Multi-Site Pig Production

Multi-site Pig Production D. L. (“Hank”) Harris Department of Microbiology College of Agriculture and Department of Veterinary Diagnostic and Production Animal Medicine College of Veterinary Medicine Iowa State University

Iowa State University Press /Ames

Multi-site Pig Production

Multi-site Pig Production D. L. (“Hank”) Harris Department of Microbiology College of Agriculture and Department of Veterinary Diagnostic and Production Animal Medicine College of Veterinary Medicine Iowa State University

Iowa State University Press /Ames

D. L. (“Hank”) Harris, DVM, PhD, is professor, Department of Microbiology, College of Agriculture, and Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, at Iowa State University. Dr. Harris returned to academia after serving as vice president of veterinary services for a commercial breeding stock company. © 2000 Iowa State University Press All rights reserved Iowa State University Press 2121 South State Avenue Ames, Iowa 50014 Orders: Office: Fax: Web site:

1-800-862-6657 1-515-292-0140 1-515-292-3348 www.isupress.edu

Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by Iowa State University Press, provided that the base fee of $.10 per copy is paid directly to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923. For those organizations that have been granted a photocopy license by CCC, a separate system of payments has been arranged. The fee code for users of the Transactional Reporting Service is 0-8138-2699-3/2000 $.10. Printed on acid-free paper in the United States of America First edition, 2000 Library of Congress Cataloging-in-Publication Data Harris, D. L. (Delbert Linn) Multi-site pig production / D. L. “Hank” Harris.—1st ed. p. cm. ISBN 0-8138-2699-3 1. Swine. I. Title. SF395 .H297 1999 636.4—dc21 99-049092 The last digit is the print number: 9

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In memory of Ken Woolley, Al Leman, and Lauren Christian Each contributed in many ways to the evolution of the swine industry, including concepts that led to modern-day multi-site pig production systems.

Contents

Foreword by R. D. Glock ix Preface xi Acknowledgments xiii 1. Introduction 3 2. Multi-site Rearing Systems 37 3. Exclusion and Elimination of Microbes 57 4. Immunity, Pig Performance, and the Emergence of Disease 79 5. Control of Common Infectious Swine Diseases 97 6. Policy Decisions and Opportunities for Owners and/or Senior Management 125 7. Management of Multi-site Rearing Systems 158 8. Breeding Stock Production 175 9. Standardized Nomenclature, Alphanumeric Notation, and Diagrams 187 10. Future Rearing Systems and Facilities 205 Index 209

Foreword

Multi-site Pig Production is the first comprehensive description of the most profound changes that have occurred in swine production methodology in many years. Techniques involving various forms of multi-site rearing have recently evolved. Dr. Hank Harris is singularly qualified to author this work because he has played a pivotal role in the initiation of techniques that are being applied throughout the world. The term isowean evolved from medicated early weaning (MEW), or isolated weaning, and was first used by Hank Harris. Its copyrighted status has been rescinded because it has become a common industry term. Terminology regarding multi-site rearing techniques has been somewhat disorderly and confusing. Information in this book provides final definition for a variety of terms that are being used to describe swine production methods. Various industry publications and glossaries have been considered in the formation of a framework for precise communication. A system of nomenclature is provided to facilitate more accurate future interactions between participants in swine production systems that involve multiple sites, buildings, and rooms with different age groups and functions. Multi-site Pig Production is designed for use by anyone interested in swine production. This includes students as well as production personnel. The writing style is easily understood and the book is arranged so it can be read in its entirety or it can be used as a chapter-specific reference. (However, no one should attempt to use this book without addressing the sections on definition of terms [Chapters 1 and 9].) The relaxed style of this book reflects the personality of the author, who has managed throughout his professional career to remain informal while providing profoundly innovative ideas. The reader may be challenged to seek further applications of some of the concepts that are presented. Major changes in disease management and, more importantly, in profitability have already occurred, but innovative applications of the information provided will result in even more significant applications. This book is a necessity for those seriously interested in the economic future of the swine industry. R. D. Glock, D.V.M., Ph.D. University of Arizona Veterinary Diagnostic Laboratory Tucson, Arizona ix

Preface

The thought of writing this book occurred to me for the first time while I was chairing a mini-symposium on multi-site production organized by Barry Wiseman and held prior to the Al Leman Swine Conference in 1997. The rather large amphitheater was filled to standing-room-only and the questions by the participants carried on well past the cocktail hour. As the symposium progressed, it became rather obvious that considerable confusion existed regarding terminology of multi-site farms and the elimination of infectious agents via isowean. In particular, Howard Hill and I couldn’t even agree on how to describe the Murphy Family Farms rearing system—a system that I helped design and that he works in every day. Several veterinarians in the room expressed the belief that multi-site production exacerbates the severity of porcine reproductive and respiratory syndrome (PRRS) outbreaks on pig farms. My reactions were Why is there so much confusion regarding a rather simple concept? (Pigs weaned in isolation away from adult swine have fewer infectious agents and grow faster on less feed.) Why can’t the other speakers and I answer all the questions posed by the participants? Does multi-site production really increase the severity of disease in some situations or is it simply due to other factors related to management and biosecurity?

Shortly after the mini-symposium, I was interviewed for a Morrison Group tape recording (see “From MEW to Multi-site Isowean Production,” Chapter 1). During the interview, those same reactions occurred plus there were more questions: How many others associated with the swine industry are having difficulty in successfully implementing multi-site technology? Are animal scientists, geneticists, pork producers, building companies, lenders, feed dealers, veterinarians, and students communicating effectively regarding multi-site production systems? Why are so many new and renovated farms using multi-site isowean technology?

The motivation to start (and finish) this book came from a fear that the Isowean Principle was correct in theory but not in practice. Was it possible that isolated weaning (isowean) should not be the basis for how most pigs in the world will be reared well into the next century? While attempting to answer this question, I learned many things by collecting information from the literature and by interviewing veterinarians and pork

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Preface

producers. As expected, not all of my original hypotheses were correct regarding the application of the Isowean Principle. But overall, I became convinced that there are many benefits to be gained by any-sized pork production operation if multi-site isowean technology is properly implemented. Thus, I felt compelled to explain the evolution, advantages, pitfalls, and practical application of modern-day multi-site pig production.

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Acknowledgments

Several individuals worked very closely with me; without their help the book would not have been finished. They are my wife, Isabel, who contributed constructive criticism to most chapters and made many significant suggestions, especially in the content of Chapter 9; Bob Glock, who edited the entire manuscript and wrote the Foreword—a true friend indeed; and Stephanie Wedel, who prepared the tables, figures, and manuscript on the computer. In the very early stages, Anita Nimtz was a very helpful assistant, and Susan Aldworth created the template for some of the illustrations. I am particularly indebted to my sons, Joel and Dill, and daughters, Wendi and Sue, for understanding my absences due to this project. There are many pork producers to thank. They are my dad, Arnie, for purchasing our first Duroc boar on the day I was born; my mom, Marie, for teaching me how to revive a chilled baby pig by the stove in our living room; my brother, Bob, for convincing me to minor in biochemistry; my sister, Patsy, and Mike Larson for use of their nursery for the first pseudorabies isowean trial; my mentors, Bill Switzer and Tom Alexander; Chuck Sand for building the first three-site farm in the world; Linus Solberg for his support even though he may disagree with the changes brought on by isowean; and Howard Hill for convincing me on the use of three-site production terminology. Many of the ideas and concepts in the book came from discussions with Joe Connor, Tim Loula, Paul Armbrecht, Steve Henry, Jack Anderson, Butch Baker, Bill Christianson, Jer Geiger, Barry Wiseman, Eldon Wilson, Jose Doporto, Jose Barcelo, Eldon Wilson, Hugh Dorminy, Randy Stoecker, and Gregg BeVier. Pork producers Gonzalo Castro, Gary Gausman, and Tim Cumberland kindly provided unpublished data found in some of the tables and figures. A special thanks to Richard Clothier for helping me create the term isowean and to Phil David for the removal of the trademark on the term by PIC (Pig Improvement Company, Inc.). The support of Iowa State University administrators is greatly appreciated and was essential for the book to be completed: Deans Richard Ross and Dave Topel, Provost John Kozak, and President Martin Jischke. I am indebted to the faculty colleagues who

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Acknowledgments

willingly increased their teaching and advising duties during my sabbatic leave: Joan Cunnick, Jim Dickson, Bob Andrews, and Chuck Thoen. I am greatly indebted to the team at Iowa State University Press. I especially appreciate Jim Ice and Gretchen Van Houten for taking the time and effort to convince me to take on the project and to keep me motivated until its completion. To my editors, Lynne Bishop and Carla Tollefson: Thanks for demanding clarity, accuracy, and completeness.

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Multi-site Pig Production

1. Introduction

Multi-site pig production refers to the rearing of the various age groups of swine at different locations or farmsteads. Tom Alexander’s (Figure 1.1) 1979 discovery that the separation of naturally farrowed piglets away from their mothers at weaning would exclude infectious agents led to a profound development in multi-site rearing technique. Tom coined the term medicated early weaning (MEW) for his discovery because he weaned the pigs early, with heavy medication, into an isolated location away from all other pigs. Based on studies whereby Tom’s approach was modified (and now is referred to as isowean), I proposed in 1987 that entire new pig farms be constructed where the three stages of production would be separated and located on three isolated sites or locations.

Figure 1.1 Dr. Tom Alexander, originator of MEW, is a lecturer in the Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, England. He has consulted for PIC for over 30 years. Dr. Alexander’s contributions to pig rearing include principles of disease control and eradication, etiologic investigations on swine dysentery, and mechanisms of disease causation by Streptococcus suis type 2.

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Multi-site Pig Production

Table 1.1 The 50 Largest Producers of Pork in the United States in 1998 Name of Operation

Murphy Family Farms Carrol’s Foods Continental Grain Company Smithfield Foods Seaboard Corporation Prestage Farms Tyson Foods Cargill DeKalb Swine Breeders Iowa Select Farms Purina Mills (Koch) Goldsboro Hog Farm The Hanor Company Land O’Lakes Heartland Pork Enterprises Farmland Industries/Alliance Pipestone System/Hawkeye Christensen Farms and Feedlots Sand Systems Bell Farms National Farms Progressive Swine Technologies Clougherty Packing Company D & D Farms Holden Farms Hostetter Management Company Lundy Packing PIC International Group, USA Texas Farms Triple Edge Pork Vall Hastings Pork/MPI Farms J. C. Howard Farms DeCoster Farms of Iowa Coharie Farms Gold Kist Hog Slat Oakville Feed and Grain Hitch Pork Production J & K Farms Wakefield Pork Consolidated Nutrition Garland Farm Supply Swine Graphics Enterprises Sand Systems Newsham Hybrids, USA Western Pork Production Corp.

Headquarters

Number of Sows

Rose Hill, North Carolina Warsaw, North Carolina New York, New York Smithfield, Virginia Shawnee Mission, Kansas Clinton, North Carolina Springdale, Arkansas Minneapolis, Minnesota DeKalb, Illinois Iowa Falls, Iowa St. Louis, Missouri Goldsboro, North Carolina Spring Green, Wisconsin Minneapolis, Minnesota Alden, Iowa Kansas City, Missouri Pipestone, Minnesota Sleepy Eye, Minnesota Columbus, Nebraska Wahpeton, North Dakota Kansas City, Missouri Columbus, Nebraska Los Angeles, California Pierre, South Dakota Northfield, Minnesota Lititz, Pennsylvania Clinton, North Carolina Franklin, Kentucky Perryton, Texas Chandlerville, Illinois Texhoma, Oklahoma Hastings, Nebraska Deep Run, North Carolina Clarion, Iowa Clinton, North Carolina Atlanta, Georgia Newton Grove, North Carolina Oakville, Iowa Guymon, Oklahoma Harrells, North Carolina Gaylord, Minnesota Omaha, Nebraska Garland, North Carolina Webster City, Iowa Farmville, North Carolina Colorado Springs, Colorado Yuma, Colorado

337,000 183,000 162,000 152,000 125,000 125,000 123,500 120,000 97,000 90,000 75,000 64,000 64,000 63,700 61,000 48,500 46,800 44,000 43,000 41,000 34,000 27,500 23,000 22,000 22,000 20,000 20,000 20,000 20,000 20,000 20,000 19,400 19,000 18,200 17,400 16,500 16,000 16,000 15,000 15,000 15,000 14,000 14,000 14,000 14,000 13,500 13,000

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Table 1.1 continued Name of Operation

Neuhoff Farms Esbenshade Mills/Hershey Ag N. G. Purvis Farms

Headquarters

Richland, North Carolina Mt. Joy, Pennsylvania Robbins, North Carolina

Number of Sows

12,000 11,500 11,000 Total: 2,599,000

Source: Betsy Freese, Successful Farming, October 1998

Multi-site pig-rearing is not a new form of production: extensive outdoor systems have been perfected in the United Kingdom and the production of 8- to 10-week-old feeder pigs (40–50 pounds body weight) occurs in most swine-rearing countries. But the multisite rearing initiated in the United States in 1988 on a newly constructed 2000-sow farm where the three main stages of pig production were placed on three separate sites was an entirely new concept. This was the first farm ever constructed specifically for the separation of recently weaned pigs away from the adult swine population. In a 1995 study by the National Animal Health Monitoring System (NAHMS) of the U.S. Department of Agriculture, it was found that 60% of U.S. pork producers with over a 10,000-head inventory were using isowean technology (moving piglets from the farrowing phase to a separate-site nursery). In 1998, the total number of sows of the top 50 U.S. producers (Table 1.1) had increased by 500,000 sows. These sows were all placed in multi-site isowean production systems. Prior to 1987, no farm in the world was built in this manner for the purpose of excluding disease. This book is about this new era of pork production and why and how modern-day multi-site systems evolved. Both the advantages and disadvantages of this approach will be discussed.

Historical Perspective Pigs of all age groups (suckling pigs through adults) were usually placed either in outside pens or within buildings in close proximity to one another. Beginning around 1950, pigs began to be reared more in confined buildings and the various stages of production became more defined: breeding, gestation, farrowing, lactation, pre-nursery, nursery, grower, and finisher. Some farmers totally confined the pigs in buildings, while others used a combination of dirt lots and buildings (semi-confined). The phrase farrow-to-finish operation was used to describe farms situated on one site that were associated with the farmstead along with the residence and buildings housing other livestock. The “feeder-pig” industry that evolved in most swine-rearing countries during the 20th century was based on rearing the pig to slaughter weight on a farm or site different than the one on which it had been farrowed, or born. Farrow-to-feeder pig farms weaned the pigs into a pre-nursery or nursery. This type of operation usually sold the pigs (at 30–50 pounds body weight and 6–10 weeks of age) to another individual, who placed them in a grower/finisher building or in open dirt lots. 5

Multi-site Pig Production

When farmers had a grower/finisher building separate from the farrow-to-feeder pig facilities, the operations were called two-site farms (now referred to as traditional two-site production). Sometimes, the grower/finisher building could only “finish” a portion of the pigs reared at the farrow-to-feeder pig facility. Feeder pigs often originated from many different (multiple) sources. Prior to 1988, both finisher pigs and breeding stock were reared either on one-site farrow-to-finish or on traditional two-site production systems.

Breeding Stock Production on One-site and Traditional Two-site Farms Until the mid-1970s, boars were almost the exclusive means of transfer of genes among farms in the United States. Purebred breeders would supply boars (rather than both boars and gilts) to slaughter-pig and feeder-pig producers, who in turn would save back their own replacement gilts. Beginning in the 1960s in the United Kingdom and about 10 years later in the United States, the pyramid system of producing both gilt and boar breeding stock originated; it has been replacing traditional purebred breeding ever since. Breeding stock companies, such as DeKalb, Kleen Lean, and PIC, were the first in the United States to promote and utilize the pyramid system, which placed a nucleus farm at the apex for development of superior genetic lines. (See Chapter 8, “Production Pyramids.”) Pyramid-style breeders created a convincing argument that genetic improvement could be made faster in the nucleus herd at the apex of the pyramid than by the producer of slaughter pigs simply utilizing rotational-cross boars. (With rotational-cross boars, commercial producers usually supplied their own replacement females for the breeding herd.) Thus, the customers were enticed into purchasing both boars and gilts from the pyramid breeder rather than simply boars from the purebred breeder. Interestingly, boars from purebred breeders were relatively free of disease due to age immunity. (See Chapter 4, “Herd Immunity.”) Since very few animals needed to be introduced into a commercial herd each year (only a few boars to maximize rotational-cross heterosis), the chance of disease introduction was quite limited. By contrast, customers of pyramid breeders needed their entire boar and gilt replacements supplied to them annually (30%–40% of the herd each year). The introduction of such high numbers of replacement animals per year increased the chance of disease introduction. In areas of high pig density, diseases are transmitted among farms quite readily. The disease status of pigs was very important because breeders, especially, could spread infectious agents to other farms by the sale of seedstock. For this reason, methods were developed to establish breeding herds with high–health status pigs. Considerable attention also has been given to development methods to limit the occurrence and transmission of disease in pig farms. George Young and Norman Underdahl (first at the Hormel Institute in Albert Lea, Minnesota, and subsequently in Lincoln, Nebraska) originated the specific pathogen–free (SPF) concept for disease control in the early 1950s. This idea spread rapidly around the world. It was adopted most successfully in Switzerland, Sweden, and Denmark, and these three countries still have a majority of their producers enrolled in the SPF program. Purebred breeders and breeding stock companies continue to use SPF techniques (surgical derivation and isolator rearing of colostrum-deprived piglets) to establish high–health status 6

1. Introduction

herds, but producers in all countries have had difficulty in keeping such herds free of pathogens on a long-term continual basis. Aujeszky’s disease (pseudorabies virus) was financially devastating to the seedstock business in the mid-1980s in the United States, United Kingdom, and some European countries. At that time, if a seedstock producer’s farm became infected with pseudorabies virus (PRV), the farmer had no choice but to stop selling breeding stock. If the farmer wished to continue producing breeding stock, total depopulation and repopulation with PRVfree stock was the only alternative.

The First Three-site Farm Because of the desire to avoid total depopulation if and when PRV infection occurred, I hypothesized that placing a farrow-to-finish farm on three sites would negate the need for total depopulation of the herd should PRV occur. Thus, the concept of three-site production originated, where the weaned pigs (3 to 10 weeks of age) were reared on a separate site from both the adult population and the older finisher pigs. Until then, weaned pigs were raised in close proximity to the adult breeding-age swine on farms. In 1988, CRB, the first modern-day multi-site pig production facility (a three-site isowean farm) in the world was constructed near Columbus, Nebraska, by Chuck Sand (Figure 1.2). It was built specifically to produce high–health status breeding stock to

Figure 1.2 Chuck Sand, builder and owner of CRB, is founder and president of Sand Livestock Systems and chairman of Sand Systems, Inc., of Columbus, Nebraska. His company was a leader in the evolution to totalconfinement pig rearing in the United States. In addition, Sand Construction has built multi-site pig production systems in many countries of the world, including the People’s Republic of China. (Photo reprinted by permission from the Omaha World Herald, Omaha, Nebraska)

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A. B.

Figure 1.3 Three-site production. A. Diagram of a three-site system. B. Aerial photograph of site 1 at CRB farm, near Columbus, Nebraska, consisting of two farrow-to-wean buildings with 1000-sow capacity each. C. Aerial photograph of site 2 at CRB consisting of one nursery building. D. Aerial photograph of site 3 at CRB consisting of 5 grower buildings and 11 finisher buildings.

decrease the financial risk associated with infectious diseases. On this farm, the various age groups (stages of production) were placed on three geographic sites separated from one another by over 2 miles. The breeding, gestation, and farrowing stages (breeding production stage)1 were on site 1, the pre-nursery and nursery stages (nursery production stage)1 on site 2, and the grower and finishing stages (finisher production stage)1 on site 3 (Figure 1.3). 1. The National Pork Producers Council Production and Financial Task Force has recommended the use of these terms to indicate the three stages of pork production.

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1. Introduction

C. D.

Although the farm was stocked with PRV-negative stock, the sows in site 1 became infected with PRV within 1 year. Vaccination of the sows at site 1 and depopulation of the nursery successfully eliminated the virus from the system. The pigs in the finisher never acquired PRV infection. Producers and industry leaders in many parts of the world quickly perceived this new approach to multi-site production was a way to avoid healthstatus deterioration associated with one-site and traditional two-site production systems and as a way to enhance pig performance and carcass quality. From 1989 through 1996, I have had personal involvement or knowledge of modernday multi-site farms being built either as modifications of existing structures or as new facilities in the United States (Nebraska, Colorado, Iowa, Oklahoma, North Carolina, 9

Multi-site Pig Production

Texas, Missouri, Minnesota, Illinois), Canada, Mexico, Brazil, Chile, Spain, Germany, Poland, Italy, Scotland, England, China, and France (see Tables 1.2 and 1.3).

Terminology Stages of Production. The three stages of production are the (1) breeding production stage, (2) nursery production stage, and (3) finisher production stage. Stage 1 (Breeding Production Stage). Production stage in which breeding females and boars are kept and managed for the purpose of producing weaned pigs. Breeding, Gestation, and Farrowing. The substages of breeding production that involve the adult females and males, including the mating (both by natural service and artificial insemination) and the gestating of sows. The farrowing substage also includes the farrowing and lactation of the young suckling piglets. Stage 2 (Nursery Production Stage). Production stage associated with nursery pigs. Pre-nursery. A substage of nursery production for rearing the young pig immediately after weaning. It is excluded from most pig farms. Nursery. A substage of nursery production for rearing the young pig either immediately after weaning or after the pre-nursery stage. The pigs are usually held in the nursery for 7 weeks. Stage 3 (Finisher Production Stage). Production stage associated with finisher pigs. Grower. A substage of finisher production for rearing the pig immediately after the nursery. It is excluded from most pig farms. Finisher. A substage of finisher production for rearing the pig either immediately after the nursery stage or after the growing stage until it is either slaughtered for meat consumption or used as a breeding female or male. Site. A site number indicates the placement for the various stages of production and the type of single- or multi-site production system. A site most often refers to the tier level of the production system. Although site sometimes is used to indicate location within a tier level, locus is the preferred term for location within a tier. Locus or Loci. Loci indicate the number of geographic locations for each stage of production at each site. Single Locus. A stage of production is placed entirely on one geographic location. Multiple Loci. A stage of production is placed on more than one geographic location. Medicated Early Weaning (MEW) (Figure 1.4). Pregnant sows are farrowed in isolation in all-in/all-out farrowing rooms away from the source herd. At about 5 days of age, piglets are weaned into an isolated nursery on a separate site. At 6 to 10 weeks of age, the pigs are transferred to an isolated grower/finisher on a third site. Prior to farrowing and during lactation, sows are medicated against the specific bacteria that are to be eliminated. 10

1. Introduction

Figure 1.4 Medicated early weaning (MEW).

Figure 1.5 Isowean (modified MEW).

The piglets are medicated during suckling and for the first 10 days after weaning. Where appropriate, the sows can also be vaccinated 3–4 weeks prior to farrowing. This is the classical procedure for MEW, but several variations of it have been applied successfully. Isowean or Modified Medicated Early Weaning (MMEW) 2 (Figure 1.5). Similar to MEW except that the sows are farrowed in the source farm in the normal way rather than in an isolated farrowing house. Also, the weaning age is variable (from 5 to 21–28 days of age), depending on the infections to be eliminated. Other terms that have been used for

2. These terms were used in Chapter 72 of Diseases of Swine, 8th ed. (1999), but I have suggested their usage be discontinued (see “Recommendations for the Use of Certain Terms,” Chapter 9 of this book). When these terms are used in Chapter 1, they are followed [in brackets] by the term recommended in Chapter 9.

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isowean or MMEW or variations of it are segregated early weaning (SEW),2 segregated weaning,2 age-segregated rearing (ASR),2 and isolated weaning.2 The term isowean is often used more widely to cover any system involving segregated or isolated weaning, which is how it is used in this book. (See also Isowean Principle.) Isowean Principle. The principle that piglets remain free from most of the serious potential pathogens endemic in a herd until after weaning (when, in traditional systems, they are sequentially exposed to pathogens from older, growing pigs). Furthermore, the piglets are likely to remain free of these pathogens if they are raised in isolated groups away from their cohorts and other age groups. This principle is the basis on which modern-day multi-site pig production systems (with the first stage of production [breeding, gestation, and farrowing] on site 1) have been developed. One-site Production (Farrow-to-Finish). All three stages of production take place on site 1 (see Figure 2.1). Historically, this is the way pigs have been raised. Two-site Production Traditional Two Site. Two-site production where stages 1 and 2 are placed on site 1 at one at one or more loci, and stage 3 is placed on site 2 at one or more loci. Prior to 1989, this was the only type of two-site production system (see Figure 2.2). The Isowean Principle does not apply. Two-site Isowean. Two-site production where stage 1 is placed on site 1 at one or more loci, and both stages 2 and 3 are placed on site 2 at one or more loci (see Figures 2.13 and 2.14). There can be one or more buildings at each locus. The Isowean Principle applies between sites 1 and 2. Three-site Production. Each of the three stages of production are located on separate sites, which are referred to as sites 1, 2, and 3 respectively. At each site, there can be one or more loci. The Isowean Principle applies between sites 1 and 2. There can be one or more buildings at each locus (Figure 1.3). Three-site Isowean Production.2 Sometimes this is simply referred to as three-site production because it is understood that the Isowean Principle applies by definition. Three-site isowean production has often been used to mean placement of facilities on only one locus at each site. In that case, multiple-site isowean production2 has been used to mean placement of facilities on more than one locus at each site. Multiple-site Isowean Production.2 This term incorporates the advantages of all-in/allout production by site for stages 2 and 3 with the advantage of isowean. Each week’s weaning fills the nursery accommodation on one site, and each week’s emptying of a nursery site (7 weeks after filling) populates the grower/finisher accommodation of one site. The disadvantage of this system is that a large number of sows are required, often in the order of 12,000, and ideally >24,000. They can be in several different loci. A synonym for this type of production system is three-site production on multiple loci. Based on the nomenclature proposed in Chapter 9, this is a type of three-site production in which pigs are reared on multiple loci. 12

1. Introduction

Multiple-site Production.2 This term is sometimes used to mean multiple-site isowean production. Multi-site Pig Production. A blanket term to cover any arrangement of sites and loci, including all types of two- and three-site production systems. The Isowean Principle may or may not apply. Multi-site Isowean Production. A blanket term to cover any arrangement of sites that incorporates the Isowean Principle, including the various possible configurations for two- and three-site production. Isowean pigs may be from single or multiple sources. This kind of production also is referred to as modern-day multi-site production. Source of Pigs. In multi-site production, source refers to either the number of sources of isowean pigs originating from a breeding production stage or the number of sources of feeder pigs originating from nursery buildings. Single Source. The pigs originate only from one locus of production. Multi-source. The pigs originate from more than one loci of production. Nursery/Finish Building. Isowean pigs are placed in a finisher building equipped to provide adequate comfort, waterers, feeders, and pens for pigs ranging in age from 2 to 3 weeks through slaughter weight. Other terms that have been used for nursery/finish buildings are NurFin and wean-to-finish. All-in/All-out Pig Flow by Site, Locus, Building, or Room. Populating a site, locus, building, or room in one day with pregnant sows at term or with pigs of the same age. The site, locus, building, or room is depopulated completely at the appropriate time (usually 2–3 weeks of age for piglets nursing sows, 6–7 weeks later for nursery pigs, and <15 weeks later for slaughter pigs), cleaned, disinfected, dried, and left empty for 5–7 days before it is repopulated. Continuous Pig Flow by Site, Locus, Building, or Room. An alternative of all-in/all-out pig flow. The site, locus, building, or room is never (or only rarely) depopulated. Since pigs are always present, there is no opportunity for total cleaning and disinfecting of the facility. Nomenclature for Pig Production Rearing Systems. A method consisting of terms, diagrams, and alphanumeric notation for describing in detail the design, location, and management of both one-site and multi-site pig production rearing systems (see Chapter 9).

From MEW to Multi-site Isowean Production “At the Meeting with the Morrison Group”3 Bob Morrison (B), Director of the Swine Center, University of Minnesota Robert Barch (R), Pork producer

3. This edited transcript of a tape recording is reprinted by permission of the Morrison Group.

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Multi-site Pig Production

Tom Wetzel (T), Swine practitioner Gordon Spronk (G), Swine practitioner With Hank Harris (H), Professor, Iowa State University B: Welcome to this edition of “At the Meeting with the Morrison Group.” Our guest today is Dr. Hank Harris. We’re going to talk about a pre-conference session that was held at the Allen D. Leman Swine Conference in September 1997. The session was called the “Nuts and Bolts of SEW Multi-site Systems,” organized by Dr. Barry Wiseman. Hank, what is SEW, which we used to call MEW, which before that was MMEW? What is age-segregated rearing? H: MEW stands for medicated early weaning, then came modified MEW, or modified medicated early weaning. Isowean is a term that was originally registered as a trademark by PIC [formerly called Pig Improvement Company, Ltd.], a large international pig breeding company. Richard Clothier, former president of PIC and I devised the term isowean during an airline flight to Colorado in 1989. Isowean was derived from two words: isolated weaning. We were on our way to participate in the groundbreaking ceremony for the second three-site farm built in the world (D&D Farms near Holyoke, Colorado). Since Isowean was a registered trademark, Lauren Christian suggested that the National Pork Producers Council (NPPC) use the term segregated early weaning (SEW) 4 for their genetic evaluation trials initiated in 1992. [Due to the suitability of the term to describe isolated weaning and multi-site produciton, PIC has released any and all restrictions of the use of this term by the general public and all individuals and companies associated with the swine industry.] Age-segregated rearing (ASR) 2 really fits in this group of MMEW2, isowean, and SEW.2 They’re all synonyms, actually, but are different from MEW. MEW was a term coined by Tom Alexander, a professor at Cambridge University in England, in 1979. Ken Woolley [Figure 1.6], president of PIC at the time, had asked Tom to develop a nonsurgical procedure for the elimination of Mycoplasma hyopneumoniae from pigs that would be used to stock new multiplier herds for the company. B: Prior to that, Hank, PIC had been creating new high–health status herds by surgically deriving pigs and rearing them in isolation? Why the need for MEW? H: Actually the motivation was cost and to try to avoid doing surgeries. . . . G: Hank, continue this history. It was interesting that day, and I think it would be interesting for our [readers] today for you to just tell us the progress of how things went after that early discovery.

4. At the time, segregated early weaning (SEW) seemed to be an appropriate term to describe this technology. Subsequently, it was shown that early weaning is not necessary to derive most of the benefits of the Isowean Principle. I recommend that isowean, rather than SEW, be used.

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1. Introduction

Figure 1.6 Ken Woolley (deceased), one of the original founders of PIC, developed the ‘Camborough,’ an F1 hybrid gilt, and convinced pork producers all over the world that “buying-in” replacement females was more profitable than producing their own replacement gilts. He stimulated research and provided the essential financial support for the development of MEW, isowean, and multisite technologies.

Figure 1.7 Keith Thornton was on the team with Dr. Alexander that developed MEW for PIC in 1979. Mr. Thornton travels the world advising pork producers on rearing and managerial procedures. He spent 2 years in Guangzhou, People’s Republic of China as general manager of a joint venture project for PIC.

H: Tom Alexander published the first paper regarding MEW about a year later. Co-authors on the paper were Keith Thornton [Figure 1.7] and Dick Lysons. But in the meantime, the PIC French company had a herd with atrophic rhinitis. PIC found that they could eliminate the Pasteurella organism that causes atrophic rhinitis by modifying MEW. B: I don’t recall that being published, is that . . . H: No, that was never published, but there was a publication from Hungary by Dr. Meszaros. He showed that they could eliminate several other agents as well as Mycoplasma by MEW with 5-day weaning. So they confirmed the work within 2 or 3 years after Tom’s original work. B: And so then they said, “Well, ok, we’re medicating these sows so much and we’re medicating these pigs so much.” Who said, “Well, let’s try it differently”? That was you, wasn’t it? 15

Multi-site Pig Production

H: It was several of us at PIC at the time, including in particular Barry Wiseman [Figure 1.8] and Eldon Wilson [Figure 1.9]. I’m not too sure if the French actually stopped isolating the sows, but it was clear that the step of removing the sows from the farm was the first thing to eliminate. And that’s really where the term modified MEW got coined. In the United States, we began modifying the procedure in some situations in PIC herds and just removing the piglets at weaning right out of the source farm.

Figure 1.8 Dr. Barry Wiseman worked with Dr. Harris at PIC on the development of isowean and multi-site concepts and then collaborated with Dr. Rodney Goodwin of the National Pork Producers Council in the United States and with Dr. Gary Dial at the University of Minnesota in definitive studies on multiple sourcing of isowean pigs. He is Vice President of Xenotransplantation Research at Nextran Corporation, a division of Baxter.

Figure 1.9 Dr. Eldon Wilson, a geneticist, was a research colleague with Dr. Harris at PIC during the development phases of isowean and multi-site technologies. Dr. Wilson is currently in charge of genetic technical development in the Americas region for PIC.

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1. Introduction

G: Can you explain how this technique really burst onto the American scene and the subsequent impact on American production? H: I think there were three things. First, PIC had a herd with App (Actinobacillus pleuropneumoniae), and it was one of those low-grade strains, hardly any clinical signs, but a lot of concern that it could cause problems downstream. We used the MEW technique, then, to repopulate a herd free of App. Second, Sarah Edgerton [Figure 1.10] and Jer Geiger [Figure 1.11], who were working with me at PIC, and I began to see if we could eliminate specific infectious agents simply by removing the piglets from each farm without removing the sows. These were the first large-scale modified MEW trials in the United States. We were able to readily exclude PRV and toxigenic Pasteurella multocida from weaned pigs by removing them from the farrow-to-finish farms. B: And so was the only modification that you left the sows in place and just removed the pigs? H: That was an important step of modification but we also varied the drugs used depending upon the organism to be eliminated. We also used vaccines in sows to enhance

Figure 1.10 Sarah Edgerton, an animal scientist, was in charge of the isowean research trials conducted by Dr. Harris at PIC in the mid- to late 1980s. She managed large production systems for PIC in the United States and the Ukraine and for Brown’s of Carolina. Ms. Edgerton is currently in charge of production of organ donor transgenic swine for Xenotransplantation at Nextran, a division of Baxter.

Figure 1.11 Dr. Jerome Geiger, an assistant to Dr. Harris at PIC, conducted the first large research trials on elimination of toxigenic Pasteurella multocida and pseudorabies virus (PRV) via isowean. Dr. Geiger is Western Regional Veterinarian for PIC Americas.

17

Multi-site Pig Production

B: H:

R: H:

B: H:

G: H: G:

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colostral protection to the piglets. The third thing that was really important as far as bringing this technology to the United States was an AASP (American Association of Swine Practitioners) meeting in St. Louis; Tom Alexander was invited to give the Howard Dunne lecture and he gave a complete review of MEW and modified MEW up until that time. So we’ve got these other terms that are synonymous with MMEW and we now call it SEW. Right, Hank? Yes some people do. I prefer isowean since I think it’s much more descriptive. I don’t like any term that has “early” in it, because it implies that we have to wean pigs early for this technique to work, which is not true. Rodney Goodwin at NPPC agrees that the preferred term should be isowean, not SEW. NPPC (Lauren Christian and Rodney Goodwin) originated the term SEW in 1992 [see Goodwin and Burroughs, 1995] because isowean was at that time a trademark of PIC. You don’t think there’s any age necessary in the isowean formula? Eldon Wilson and I found a tremendous improvement in performance by using isowean with 21-day weaning. Several different universities and companies have confirmed our findings that if you isolate pigs out of an existing, say, farrow-to-finish farm and compare those isolated, weaned pigs to their littermates in the farm, the performance effect is quite profound. But, Hank, at what age do you isolate them? The only time that you have to be careful about weaning age is if you specifically are trying to eliminate an infectious agent. That varies with the infectious agent that you’re trying to eliminate. So therein lies part of the confusion, if you just weaned pigs off site, or isolated as you like to use the term, there’s a performance enhancement. Right. But then the second leg of that, which apparently people have automatically layered on top of this technique is they’ve suddenly said, “Well, let’s eliminate a disease.” So then, like Dr. Sandra Amass pointed out in her paper, people just sort of go to the chart, pick a disease, pick a wean date, and well, that’s it, we’ve eliminated that disease. Unfortunately that occurs. To get the performance effect, you don’t necessarily have to eliminate infectious agents, and so I think producers and veterinarians have to be very careful about what their objectives are, and they have to remember who they are as well. If you’re a breeder, then the objectives change and become quite specific regarding infectious agents. Whereas if you’re a commercial operation, the most important thing is to get the performance effect on a consistent basis. What’s your theory as to why you’re getting that performance effect, then, if it’s not an infectious agent reason? It’s clear that you can get this performance effect even from high–health status herds. Dr. John Patience, from the Prairie Swine Center in Saskatoon, presented evidence that even isolating healthy pigs resulted in improved performance. . . .

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1. Introduction

T: Hank, would you say when you developed isowean in this country that your idea was not necessarily to utilize the multi-site technology at the same time? In my mind, the multi-site technology has been bastardized an awful lot, and I know that’s what we’re going to talk about here today somewhat is the different ways that people are utilizing that system. It seems to me that we got hung up as veterinarians on eliminating diseases and worrying about that more than performance, and not realizing that there were some very basic things that we can deal with from the standpoint of age segregation with pigs that will improve performance because of lateral infections. H: Right. It might be a good time to back up just a bit and think about the evolution of this system. In the 10 years following 1979, the various people involved were concerned about producing batches of pigs free of specific infectious agents to stock new herds. That was the purpose of MEW and isowean (modified MEW). Now, in the mid-1980s we woke up to the fact that we were seeing this tremendous performance improvement. We could consistently produce 80-pound pigs at 80 days of age— which was pretty exciting, at least at that point. In 1988, Ken Woolley at PIC wanted to know if there was a way to apply isowean technology from the very beginning of building new herds or new structures. And with that in mind, we really came up with these ideas of multi-site farms. B: Why? You had already proven with isowean that you could produce these pigs that were clean and performed well. Why did you have to go multi-site? H: PIC in the mid-1980s, as well as other producers, was having difficulties rearing seedstock free of pseudorabies virus (PRV). Ken Woolley said to me, “Look, can’t you design a system in which if it gets pseudorabies, you’ll never have to depopulate the sow farm?” And so the whole reason for multi-site was driven by a breeder, PIC, saying, “Let’s come up with a system that we don’t have to do whole-herd depopulations any longer.” B: Trying to decrease risk. It had nothing to do with performance per se. H: Correct. And by that time, we had done at least one study where Paul Armbrecht [Figure 1.12], Barry Wiseman, and I worked with a PRV-infected herd owned by the Oswald Brothers near Ft. Dodge, Iowa. It was a farrow to half-finish herd in the middle of Iowa that had been vaccinated for PRV. We simply weaned the pigs at 3 weeks of age into an isolated nursery and were able to consistently produce PRV-negative pigs. H: It was actually just another modified MEW trial. But it was what led me to propose to Woolley that we could build a new farm the same way we had modified the Oswald farm to run the study. I’ll always remember when Ken Woolley called me into his office on Easter Sunday in 1988 and said, “You know, I’ve spent enough money on your research, Harris. It’s time to really get some payback on this thing.” And he asked me to go to the board and draw up some different systems that he could sell to prospective multipliers to develop farms that they wouldn’t have to depopulate. So that Easter Sunday morning, I diagramed three-site and multiple-site concepts to Ken.

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Multi-site Pig Production

Figure 1.12 Dr. Paul Armbrecht, a veterinary swine practitioner in Lake City, Iowa, has been an independent veterinary consultant to pig breeding stock companies and producers for over 20 years. Dr. Armbrecht conducted some of the first trials on elimination of pseudorabies virus (PRV) by isowean and then helped farmers enlarge their swine operations via conversion to three-site isowean systems.

In three site [three site (single source, single locus)],5 site 1 was breeding, gestation, and farrowing; site 2, the nursery; and site 3, the finisher. Multiple site [three site (multi-source, multi-loci)]5 was different. I suggested a nursery in a different location for the first week’s production, and then the second week’s production would go into another isolated nursery, and so forth. So multiple site is quite different than three site in that, as the name implies, three site means that there’s just a sow farm with breeding, gestation, farrowing; one nursery location; and one finishing location, but there is a separate all-in/all-out nursery room for each batch of weaned pigs. G: And ultimately multiple site [three site (multi-source, multi-loci)] would be one week’s worth of production or maybe even one day’s worth of production for a site [locus].6 H: Right, all in/all out. The first farms were three site and all-in/all-out by nursery room and all-in/all-out by finisher building. I suggested 5000 sows at the first one, and Ken settled on 2000 sows, thinking that was more practical. Chuck Sand built a 2000sow three-site farm for PIC multiplication, then, in the next few months. Subsequently, Chuck in Nebraska and Dave Leurs and Dave Synder in Colorado built several more three-site farms. The creation of these three-site farms for multiplication evoked considerable discussion by the PIC management team. Ken Woolley, Randy Stoecker [Figure 1.13], Hugh Dorminy [Figure 1.14], Eldon Wilson, Barry Wiseman, and I spent many hours debating this concept. The multiple-site [three site (multi-source, multi-loci)] approach was started around 1989 after Randy joined 5. In the original tape recording, the terms three site and multiple site were used. Subsequently, these terms were redefined. I recommend using the terms placed in brackets [ ] after three site and multiple site (see Chapter 9, “Recommendations for the Use of Certain Terms”). 6. This is an example of where the word locus, rather than site, is preferred.

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Figure 1.13 Randy Stoecker, an early believer in multi-site production concepts, was Vice President of Operations for PIC in the mid-1980s. He later joined Murphy Family Farms in North Carolina and in 1989 convinced the company to build the first multiple-site isowean system in the world. Mr. Stoecker is currently President of Midwest Operations for Murphy Family Farms.

Murphy Farms in North Carolina. Later, Hugh developed a large multiple-site system, in Arkansas for Cargill, that has been quite successful. G: Well, Hank, that clarifies terminology and has given us a perspective of the history. However, there was even another term that came up that day at the meeting. Howard Hill talked about single source versus multi-source. We’ve layered on another complexity with regard to whether or not the pigs come from one sow farm [single source]7 or multiple sow farms [multi-source]7 when you start running these systems. H: I was always concerned about the three site [three site (single source, single locus)] concept. I knew there would only be one nursery site, and even though you might have all in/all out rooms, it would be under a continuous flow situation, and the reasoning was to produce pigs free of certain agents that the sow farms were positive for so you wouldn’t have to depopulate the sow farm. Then you could still sell breeding stock out the bottom. Well, obviously there’s a problem if the sow farm becomes positive. In a three-site system, you may have to depopulate the nursery or even the finisher complex if you’ve got an unwanted infectious agent. If you add many different sources of pigs to a nursery in a three-site system, you increase the chance that you may contaminate the nursery and even the finisher.

7. These terms in brackets [ ] are as proposed in Chapter 9.

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Multi-site Pig Production

Figure 1.14 Hugh Dorminy, in a trio with Dr. Harris and Randy Stoecker, was the devil’s advocate regarding multi-site production when he was Vice President of Production and Transport at PIC in the early 1980s. He is now General Manager at Cargill Pork and has developed a large multiple-site isowean system involving over 100,000 sows.

In theory, the multiple site [three site (multi-source, multi-loci)] is the best of all worlds. It was discovered that 3-week-old pigs could come from many different sources, go into an all-in/all-out nursery by week flow, and have very few disease problems. In fact, Barry Wiseman and Rodney Goodwin [Figure 1.15] did a study at the University of Minnesota, sponsored by the National Pork Producers Council, where they mixed pigs from 70 different herds, and we were all amazed at the number of agents he was able to eliminate in that study. Some agents came through, of course, especially those pigs weaned at 21 days. . . . G: But Hank, it seems that Howard Hill of Murphy Farms introduced a new dimension regarding the number of sources of isowean pigs. H: Yes, it’s based on his own experience at Murphy Farms with multiple-site isowean systems [three site (multi-source, multi-loci)] as well as some work out of Canada by Godbout and co-workers. There is a performance advantage to placing single-source isowean pigs into nurseries as compared to pigs from multiple sources. There may have been a detrimental effect if you were mixing feeder pigs (at 40 pounds body weight). 22

1. Introduction

Figure 1.15 Dr. Rodney Goodwin is Vice President for Research at the National Pork Producers Council, Clive, Iowa. Dr. Goodwin was responsible for the NPPC genetic evaluation project at the University of Minnesota with Drs. Barry Wiseman and Gary Dial.

B: But isn’t that part of the problem? In my opinion that’s why this session was so popular. Confusion lies in the fact that Wiseman and Goodwin can present data that says, “Listen, you can have up to 70 or 80 sources, and look at the good performance we have,” but yet when people went and did this in real life, they had failures. Is that true? H: The real-life failures are due primarily to the fact that people are mixing pigs into the continuous flow nurseries on one location. I think that’s the main reason for the failures if they have multiple sources. T: So they’re not all in/all out by site, they’re all in/all out by room. H: Right, and I still think this is one of the most confusing things in the industry today. Some producers assume that if they utilize isowean then the pigs will automatically perform better. B: Over time, the health status will eventually decline to a point where you’re back where you started. H: Right, and that’s going to take place whether you have one farm or multiple farms supplying that one nursery. Scott Dee recently published a review article regarding the production of PRRS [porcine reproductive and respiratory syndrome]-negative pigs via isowean. He indicated that a PRRS virus–positive sow farm produced PRRSnegative isowean pigs initially, but then the nursery became positive for the virus. That’s what you would expect. If you have a relatively calm, or stabilized, sow farm for PRRS, most batches of isowean pigs, by week, would be PRRS negative. But if you weaned all the pigs into a one nursery building, it just takes one week’s production to be PRRS positive, and then you’ve introduced the virus into the nursery. So, unless you depopulate that nursery as you would in a multiple-site isowean [three site (multi-source, multi-loci)] system, then you’re still dealing with PRRS in the nursery. 23

Multi-site Pig Production

B: Gordon, are you finding that in your Pipestone system? You presented a paper called “Multi-site Production,” explaining why this is essential to your Pipestone system. G: Well, I guess our system is single-source multiple-site isowean [three site (single source, multi-loci)]. In most cases, a farmer gets a group of pigs from one sow source, brings it to his nursery, and runs that group through his nursery as a cohort of pigs. They never get exposed to another group of pigs. Then they move as a group to a finisher, which may be off site. We may define off site as only a hundred yards away. B: And that nursery room then is depopulated, washed out, and a new group of pigs comes in. G: In both the nursery and the finisher. So to get to your question, “Do we see the problems that Hank just described”? Well, eventually you have a group of positive pigs come through. I think that’s probably true. I think in most cases, these groups of pigs perform very well, but over time, a group may pop up with some pathogen. The case Hank was just referring to was PRRS. I think that’s probably true. We would consider our sow farms to be positive, but yet in most cases, we produce negative PRRS pigs. H: You are usually running all-in/all-out nurseries then? G: Correct. H: Right. See, I think that may be unique. I think there are a lot of people who aren’t able to do that. G: I think you’re exactly right, Hank. These farmers have their own individual nurseries and their own individual finisher floors; they can run all in/all out by site. B: And so, Gordon, your data are phenomenal if you compare it to some of the large industry players. You’re top 10% of your herds from, lets say, 9 pounds to 65 pounds, average 1.15 pounds per day, with a 0.5% mortality. T: When you look at the system that is being developed with networks, this is really intriguing. Potentially, what Gordon has described here is a system that is more than competitive with the large players in the industry. Simply because what Gordon has is anywhere from an 8- to 24-site production system. And at the minimum, Hank, he is introducing pigs only once every 8 weeks. That’s the minimum amount of time between groups of introduction of pigs to one site. And the most groups you’d have on one site, Gordon, would be three. Is that correct? G: Maybe, it would depend on the individual farmer, but if he had two groups, they might be the same age. In other words, they might have been filled all at the same time. T: I would count that as one group. Then it would be 8 weeks before you introduced another group? G: Correct. That’s exactly right. H: Which is the intent of the original definition of multi-site isowean systems. B: And so when we look at Godbout’s data in Howard [Hills’] paper, he’s saying, “When you compare single source to multi-source, they went from 1.63% single-source mortality in the nursery up to 4% when they had multi-source, and in finishing, they went from .92% mortality up to close to 3% mortality.” So Hank, what we’re seeing as we go from single source to multi-source is that we really screw up those pigs in a 24

1. Introduction

H:

B:

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sense. But you’re saying, “Well, it’s not the source effect, it’s when you don’t do multiple-site isowean [three site (multi-source, multi-loci)] and you don’t depopulate that nursery or finisher.” Let’s be careful in that the data Howard [Hill] presented was based on an all-in/all-out nursery single-source multiple-site isowean [three-site (single source, multi-loci)] system. This means there was a nursery depopulation between fills. So there was a source effect as well. The ideal system is single-source multiple-site isowean. If you can afford the cost of that, where you can do all-in/all-out by site and fill it with a single source, that’s going to give you the highest health, and in turn the highest performance. . . . Well, when you take a look at this from an economic perspective, and I think, Hank, you said it’s difficult and the reason it’s difficult is that single-source multiple-site isowean [three site (single source, multi-loci)] systems are extremely capital intensive. Now we’re trying to minimize our variable components, which are feed expense and some of our yardage expenses. But a lot of it’s fixed, because we’re going to pay that yardage on that building whether it’s empty or not, so to me that’s a fixed component, and so we need to look at the total cost curves and marginal cost curves. And some will say, “Why aren’t we going to 600-sow farrow-to-finish barns because, look, our capital costs are less, we’ve got less transportation, we’ve got less sites, less headaches, and less moving, and when we keep the sows clean, it looks like it works, and performance starts rivaling the multi-site system.” So what do you say to the Canadian people when we give you that kind of rebuttal to the multiple-site isowean system? Well, what I say to them, and what I said in the meeting is that it’s quite possible they should continue to build farrow-to-finish farms. I don’t think this system’s for everybody. Maybe the best way to make this point is the reaction of Wendell Murphy to me when I drew out multiple-site isowean for him. As soon as Wendell saw that there was an opportunity for using somebody else’s capital to build contract nurseries instead of his, he went for it. So that’s a different deal than somebody who’s a producer with a 600-sow farrow-to-finish farm. Perhaps a lot of veterinarians reason that multiple-site isowean systems are being built for either performance or disease elimination, when in fact it may be pure economics and primarily capital driven. . . . Hank, what were the take-homes you think the audience left with? I asked the speakers to clarify the following points: (1) multi-source versus single source; (2) early weaning versus isolated weaning; and (3) profit comparisons between farrow-to-finish versus multi-site isowean farms. It’s the isolated weaning rather than how early you wean the pig that is significant. I challenged the speakers to tell us where the money is and why people are doing multi-site production. Where’s the profit? Another area that didn’t really come up to any great extent is the work by Tim Stahly and Noel Williams over the last 4 to 5 years at Iowa State University. They’ve 25

Multi-site Pig Production

R:

G: R: B: H: B:

shown that isowean pigs not only grow faster, but their lean gain rate also is much better compared to traditionally reared pigs. It was suggested today and in the meeting that single-source pigs are better, so I asked [Howard] Hill if building 10,000sow breeding-gestation-farrowing farms is really risk-free as well. Once these site 1 sow farms get so big, will there be increased economic risk from them? I think there are two reasons to go with multi-site [three site (single source or multisource, multi-loci)]. One, it’s growth ability. You can grow the system incrementally without having to lay down $2 or $3 million at a crack. Two, multi-site has firewalls in the system all over the place. It reduces your risk. Risk reduction, and I wouldn’t want to have $50 million worth of livestock on one site and not have any firewalls in the system. Hank, we’d like to thank you very much for joining us on this tape. You’re welcome. I enjoyed it. And we’ll see you next time “At the Meeting with the Morrison Group.”

Multi-site Production from 1987–1998 Paul Armbrecht (veterinarian from Lake City, Iowa), Barry Wiseman of PIC, and I developed the “Oswald Project” in 1987. The Oswald Brothers owned a farrow to one-half finish boar multiplier for PIC that had become infected with PRV. We got approval from PIC to try to exclude PRV by isowean in a large field trial. There were many skeptics among veterinarians and colleagues because PRV is a herpesvirus that may permanently infect some pigs. I arranged to send the 3-week-old weaned pigs to a nursery building (owned by my sister, Patsy, and her husband, Mike Larson) in Kanawha, Iowa, which was located about 40 miles north of the Oswald farm. The pigs were subsequently placed in a finisher building owned by Gene Black near Ft. Dodge, Iowa, but well away from the Oswald farm and other pigs. Hundreds of pigs were produced free of PRV in this project, and it was the final experiment that gave me confidence to suggest to Ken Woolley that new farms be constructed on three sites. The results of this study were published in 1992. As previously noted, the first three-site (single source, single locus) farm, consisting of 2000 sows, was built by Chuck Sand in 1988 in Nebraska (Figure 1.3). Beginning in 1989, Murphy Family Farms in North Carolina started building three-site (multi-source, multi-loci) isowean farms consisting of two 3600-sow facilities at site 1. The nursery buildings were constructed on isolated loci to accommodate 1 week’s weaning from both sow farms. The nurseries were well isolated from the loci in site 1 and site 3. The finishers were placed on isolated loci to accommodate 1 week’s worth of weanings that had been transferred from the nursery buildings. Murphy Family Farms had previously contracted with local farmers to build finisher buildings to receive 40- to 50-pound feeder pigs owned by the company. With the threesite production system, Murphy’s began supplying 3-week-old pigs to contract growers with site 2 nurseries on multiple loci. Subsequently, the pigs were moved to contract 26

1. Introduction

growers with site 3 finisher facilities on multiple loci. Murphy Family Farms maintained ownership of the pigs to slaughter weight. Harold Trettin in Rockford, Iowa, made the first conversions from a traditional two-site system to a three-site (single source, single locus) farm in 1989. By doing this conversion, Harold expanded his operation from a 600-sow farrow-to-70% finish to a 1200-sow farrow-to-100% finish. He was also able to eliminate pseudorabies virus without depopulation. Beginning in late 1989, Chuck Sand in Columbus, Nebraska, and D&D in Holyoke, Colorado, began building a series of additional three-site (single source, single locus) farms. Also in 1989, Joe Connor, a veterinarian from Carthage, Illinois (Figure 1.16), advised Carroll Farms (owned by Dan, David, and Darel Carroll of Carthage), which was a

Figure 1.16 Dr. Joe Connor, of Carthage Veterinary Clinic, Carthage, Illinois, was the first veterinary practitioner in the United States to utilize isowean technology on his clients’ farms. Dr. Connor pioneered the development of the wean-tofinish buildings.

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Multi-site Pig Production

multiplier farm for Lieske Genetics, to wean gilts into an isolated nursery and to finish them in an isolated finisher building. Carroll Farms called these pigs “clean-wean” gilts because of their high–health status. Beginning in 1989, Al Leman and Gene Barrick at Swine Graphics, Inc., in Webster City, Iowa, created several multi-site farms with traditional producers. Many of these were conversions of one-site or traditional two-site farms to two-site isowean systems. On site 2, either a new nursery was constructed or existing farrowing rooms were converted to nursery accommodations. Menard Farms in Quebec, Canada, began utilizing a three-site system for slaughter-pig production in 1990. Genetiporc Company began producing breeding stock by three-site production in Minnesota in 1991 and in Canada in 1992. Camille Moore (Figure 1.17) from Canada and Rod Johnson (Figure 1.18) in Minnesota were key veterinarians contributing to these systems. Hugh Dorminy at Cargill began building a three-site (multisource, multi-loci) system near Russellville, Arkansas. The Porgen Company (owned by Gonzalo and Manuel Castro) built the first three-site (single source, single locus) farm in Chile for the production of breeding stock in 1990. Serving as general manager of Super Pollo, Swine Division, Gonzalo Castro (Figure 1.19) established a large three-site (single source, multi-loci) system in 1993. Under Gonzalo’s leadership, and subsequently Marcus Garcia, Super Pollo has without question the most superior production performance records for pig production worldwide (Figures 1.20 and 1.21). Jose Manuel Doporto (Figure 1.22) of Mexico City was instrumental in advising the Proan Company to build a large multiple-site isowean system in 1990 in San Juan de Cos, Mexico, for the production of PIC breeding stock. In 1991, Grupo Poricolo Yucatan and Univasi in Cancun near Merida, Mexico, began constructing a 30,000-sow multiple-site

Figure 1.17 Dr. Camille Moore of St. Cesaire, Quebec, Canada, helped Genetiporc establish three-site farms in both the United States and Canada.

28

1. Introduction

Figure 1.18 Dr. Rod Johnson of Morris, Minnesota, set up Evergreen Farm, the first three-site multiplier for Genetiporc in the United States. He is past president of the American Association of Swine Practitioners.

Figure 1.19 Dr. Gonzalo Castro is coowner of Porgen and the former general manager of Super Pollo Company in Chile. Dr. Castro is on the senior management team of PIC.

isowean system. Ken Woolley, Gregg BeVier, Steve Thomas, and Jer Geiger were instrumental in providing technical assistance in this venture. DeKalb Swine Breeders began building three-site breeding stock production farms in Oklahoma in 1990. PIC built a three-site (multi-source, multi-loci) system in Oklahoma beginning in 1991. Newsham Hybrids built a three-site (multi-source, multi-loci) system in Colorado beginning in 1991. 29

Multi-site Pig Production

Figure 1.20 Aerial view of Super Pollo multiple-site isowean system in Chile. A nursery locus is in lower right and four large all-in/all-out finisher loci are in the middle of the photograph.

Figure 1.21 Number of pigs weaned per sow per year for the various Super Pollo herds in Chile in 1997.

30

1. Introduction

Figure 1.22 Dr. Jose Doporto is a pathologist and a specialist in swine performance record analysis. He is a university professor and has been a consultant to PIC for over 25 years.

Figure 1.23 Dr. Jose Barcelo developed the 1000-point scoring system for determining the biosecurity level of swine farms. He has been a consultant to PIC for over 15 years.

Jose Barcelo (Figure 1.23) of Barcelona, Spain, advised CEFUSA of the Comunidad Autonoma de Murcia in Spain to co-mingle isowean pigs from five different sources of variable health status in a large three-site system beginning in 1992. Tables 1.2 and 1.3 list the various multi-site isowean systems built around the world from 1988 through 1996. The list is not inclusive but is an attempt to document the first usage of multi-site isowean technology in each country. 31

Multi-site Pig Production

Table 1.2 Evolution of Early Multi-site Isowean Breeding Stock Production Year

Company

Breeding Stock Herd

Multi-site System

State/Country

Owner

1988 1989 1989 1989 1990 1990 1990 1991a

PIC PIC PIC Lieske PIC DeKalb PIC Genetiporc

Multiplier Multiplier Multiplier Multiplier Nucleus Nucleus Multiplier Nucleus

Three Siteb Three Siteb Three Siteb Three Siteb Three Siteb Three Siteb Three Sitec Three Siteb

Nebraska, USA Rockford, Iowa, USA Colorado, USA Illinois, USA Santiago, Chile Oklahoma, USA San Juan de Cos, Mexico Minnesota, USA

1991

PIC

Three Sitec

Oklahoma, USA

1991 1992 1994 1994

Newsham Genetiporc PIC PIC

Newsham Genetiporc Agroceres PIC

Lieske PIC

Minnesota, USA Long Island, Kansas, USA

Lieske Cox

1996 1996 1996 1997

PIC PIC PIC PIC

Multiplier Multiplier Multiplier Multiplier

Jutland, Denmark Poland Soria, Spain England

Dohrman Poldanor Valls PIC

1997 1997

PIC PIC

Genetic Nucleus Nucleus

Shanghai, China France

PIC PIC

1998

PIC

Scotland

PIC

1998

PIC

Production Nucleus Multiplier

Three Sitec Three Siteb Three Siteb Two-Site Isoweand Three Siteb Two-Site Isowean Three Siteb Three Sitec Three Siteb Outdoor Isoweanb Three Siteb Two-Site Isowean Three Siteb

Colorado, USA Canada Lagos MG, Brazil Germany

1994 1995

Production Nucleus Nucleus Nucleus Multiplier Al Boar Production Multiplier Multiplier

Sand Trettin D&D Carroll Farms Porgen DeKalb Proan Evergreen Partner PIC/Lamb

Three Sitec

Germany

Danials

a After 1990, farms were only included if they were either the first multi-site isowean farm in a country or the first type of multi-site system in a country. b single source, single locus c multi-source, multi-loci d multi-source, single locus

New Developments The following recent developments are discussed in detail elsewhere, but each is worthy of a brief special note.

Nursery/Finish Buildings (NurFin, Wean-to-Finish Buildings) Three individuals have been instrumental in the creation and development of combined nursery and finisher buildings. These people are Bob McCulley, Oakville Feed and Grain, 32

1. Introduction

Table 1.3 Evolution of Early Multi-site Isowean Commercial Pig Production Year

1989 1989 1990 1990 1991 1991 1991 1992 1992 1992 1992 1992 1993a 1993 1993 1994 1994 1996 1996 1996 1996 1996

Owner

City/State/Country

Multi-Site System

Murphy Family Farms Swine Graphics Sand Menard Univasi Grupo Poricolo Yucatan Robitailleet Fils, Inc. National Farmse CEFUSA Iowa Select Farms Pipestone Cargill Super Pollo Carroll Foods Paladini Perdigao Oakville Feed and Grain Poldenor Veronaris Westfliesch BOCM Pauli NFZ

Rose Hill, North Carolina, USA Webster City, Iowa USA Columbus, Nebraska, USA Quebec, Canada Merida, Mexico Merida, Mexico Quebec, Canada Dahlhart, Texas, USA Murcia, Spain Iowa Falls, Iowa, USA Pipestone, Minnesota, USA Russellville, Arkansas, USA Santiago, Chile Mexico Argentina SanteCata Rina, Brazil Oakville, Iowa, USA Poland Italy Germany United Kingdom Germany

Three Sitec Two-Site Isowean Three Siteb Three Siteb Three Sitec Three Sitec Three Sitec Three Sitec Three Sitec Three Sitec Three Sited Three Sitec Three Sitec Three Sitec Three Siteb Three Sitec NurFin Isowean Three Sitec Three Sitec Three Sitec Three Sitec Three Sitec

a After 1992, farms were only included if they were either the first multi-site isowean farm in a country or the first type of multi-site system in a country. b single source, single locus c multi-source, multi-loci d single source, multi-loci e purchased by Continental Grain 19

Oakville, Iowa; Joe Connor, Carthage Veterinary Clinic, Carthage, Illinois; and Frank Brummer, Farmweld Company, Teutopolis, Illinois. Beginning in 1994, Bob and Joe first modified an existing finisher building to accommodate 3-week-old weaned pigs. The size of the pens was reduced, nipple waterers were added, and supplemental heat was provided. The pigs remained in the building until sold to slaughter. Subsequently, Mike, working closely with Joe Connor, has become a leading manufacturer and innovator of nursery/finish buildings and equipment. The significance of this development is only just being realized by the swine industry. Nursery/finisher buildings will likely enable pork producers on farms with small numbers of sows to maximally utilize the Isowean Principle and all-in/all-out production for improved performance and infectious agent elimination (Chapters 2 and 3).

Elimination of Infectious Agents from Site 1 Without Depopulation Jorgan Plomgaard has recently eradicated three infectious agents (Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, and porcine reproductive respiratory [PRRS] 33

Multi-site Pig Production

virus) from site 1 in a 600-sow three-site farm in Denmark. Mireille Mausservey has successfully eliminated PRRS virus without depopulation of sows on several one-site farms in France. This is an extension of the methods developed by W. Zimmermann for elimination of M. hyopneumoniae without total depopulation from traditional one-site farms in Switzerland. Furthermore, Poul Baekbo in Denmark and Bjorn Lium in Norway confirmed the work of Zimmermann, particularly in small, traditional one-site farms. The methods developed by Zimmermann were based on removal of the younger pigs from the premises and on retention of the breeding stock older than 10 months of age. It is believed that the older, previously infected breeding stock no longer shed certain infectious agents later in life. Thus, the sow herd becomes free of the infectious agent(s) without total depopulation (Chapters 3 and 5). Based on these studies, perhaps the biggest advantage of modern-day multi-site production systems will be elimination of pathogens from site 1 in addition to exclusion by isowean.

Standardized Nomenclature, Alphanumeric Notation, and Diagrams Isabel Harris and I have developed an alphanumeric notation scheme for describing various types of one-site and multi-site systems. A complete glossary, key to terms and symbols, and diagrams for multi-site notation are presented in Chapter 9. In 1995 Earl Dotson created a large task force, chaired by Will Marsh, for the National Pork Producers Council to establish a standardized production and financial terminology for the pork industry in the National Pork Production and Financial Standards Technical Manual. I have used their production terms throughout this book. At the time of submitting this book for publication, the task force was initiating deliberation on multi-site production terminology.

Bibliography Alexander, T.J.L., and D.L. Harris. 1992. Methods of disease control. In Diseases of Swine, 7th ed., ed. A.D. Leman, B.E. Straw, W.L. Mengeling, S. D’Allaire, and D.J. Taylor, 808-836. Iowa State University Press, Ames, Iowa. Alexander, T.J.L., K. Thornton, G. Boon, R.J. Lysons, and A.F. Gush. 1980. Medicated early weaning to obtain pigs free from pathogens endemic in the herd of origin. Veterinary Record 106:114-119. Amass, S. 1997. The effect of wean age on pathogen removal. Nuts and Bolts of SEW Multi-site Systems, 20-32. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Baekbo, P., K.S. Madsen, M. Aagard, and J. Szancer. 1994. Eradication of Mycoplasma hyopneumoniae from infected herds without restocking. Proceedings of the 13th International Pig Veterinary Society Congress, Bangkok, Thailand, 135. Castro, G. 1998. Personal communication. Connor, J. 1990. Modified medicated early weaning. Proceedings of the American Association of Swine Practitioners, 261-265.

34

1. Introduction

Connor, J. 1994. New innovations in building design: Wean-to-finish. Unpublished presentation at the annual meeting of the American Association of Swine Practitioners, Chicago, Illinois. Dee, S.A. 1997. Elimination of PRRS virus: Is it possible? Large Animal Practice 36-38. Freese, B. 1998. Pork powerhouses 1998. Successful Farming, October (1998):19-23. Godbout, D., M. Bonneau, D. Boyaud, B. Couture, and G.P. Martineu. 1996. Segregated early weaning: Impact of number of sources of piglets on growth performances in nursery and growing/finishing. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 479. Gomez, M., E. Cervantes, D. Basto, R. Vargas, C. Canto, J.R. Bustos, and J. Cordoba. 1996a. Isowean multi-site production system in the tropics: A performance review. I. Reproductive performance. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 480. Gomez, M., E. Cervantes, D. Basto, R. Vargas, C. Canto, J.R. Bustos, and J. Cordoba. 1996b. Isowean multi-site production system in the tropics: A performance review. II. Growth performance, Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 481. Goodwin, R. 1997. Five rules of commingling SEW pigs. Nuts and Bolts of SEW Multi-site Systems, 14a-14d. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Goodwin, R.N., and S. Burroughs. 1995. NPPC Terminal Sire Line National Genetic Evaluation Results. National Pork Producers Council, Des Moines, Iowa. Harris, D.L. 1988a. Alternative approaches to eliminating endemic diseases and improving performance of pigs. Veterinary Record 123:422-423. Harris, D.L. 1988b. New approaches for the elimination of infectious diseases from swine. Proceedings of the 92nd Annual Meeting of the U.S. Animal Health Association, Memphis, Tennessee, 416-426. Harris, D.L. 1990a. Isolated weaning—Eliminating endemic disease and improving performance. Large Animal Veterinarian 10-12. Harris, D.L. 1990b. Isolating early weaners can stop disease. International Pigletter 10(2):5-8. Harris, D.L. 1993. From medicated early weaning to age-segregated rearing techniques for improving performance and disease control for swine. Animal Health Forum 7:1-4. Harris, D.L. and T.J.L. Alexander. 1999. Methods of disease control. In Diseases of Swine, 8th ed., ed. B.E. Straw, S. D’Allaire, W.L. Mengeling, and D.J. Taylor. Iowa State University Press, Ames, Iowa. Harris, D.L., S.L. Edgerton, and E.R. Wilson. 1990. Large thymus glands in isowean pigs. Proceedings of the 11th Congress of the International Pig Veterinary Society, Lausanne, Switzerland, 291. Harris, D.L., P.J. Armbrecht, B.S. Wiseman, K.B. Platt, H.T. Hill, and L.A. Anderson. 1992. Producing pseudorabies-free swine breeding stock from an infected herd. Veterinary Medicine February:166-170. Hill, H. 1997. Single sourcing versus multiple sourcing in multi-site production systems. Nuts and Bolts of SEW Multi-site Systems, 3-9. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Johnson, R.G. 1992. MMEW post-weaning performance: “Life in the fast lane.” Proceedings of the American Association of Swine Practitioners 1992:463-467.

35

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Klasing, K.C. 1994. Interactions between nutrition and immunity. Allen D. Leman Swine Conference. Vol. 21. 1994, 35-39. Veterinary Outreach Programs, University of Minnesota, St. Paul. Lium, B., A. Skomsoy, A. Jorgensen, B. Loe, and J. Szancer. 1992. An attempt to eradicate Mycoplasama hyopneumoniae from selected Norwegian farrowing-to-finishing herds. Proceedings of the 12th International Pig Veterinary Society Congress, St. Paul, Minnesota, 300. Meszaros, J., L. Stipkovits, T. Antal, I. Szabo, and P. Veszely. 1985. Eradication of some infectious pig diseases by perinatal tiamulin treatment and early weaning. Veterinary Record 116:8-12. National Animal Health Monitoring System (NAHMS). 1995. Part I: Swine Management Practices, 1-22. Veterinary Services, Animal and Plant Health Inspection Service, U.S. Department of Agriculture. National Pork Producers Council. 1998. National Pork Production and Financial Standards Technical Manual, edited by Will Marsh. National Pork Producers Council, Des Moines, Iowa. Plomgaard, J. 1998. Eradication of PRRS from the swine herd. Allen D. Leman Swine Conference. Vol. 25. 1998, 194. Veterinary Outreach Programs, University of Minnesota, St. Paul. Spronk, G., B.R. Kerkaert, J.D. Bobb, G.F. Kennedy, and J.L. Goetz. 1997. Multi-site production: Why this is essential to our system. Nuts and Bolts of SEW Multi-site Systems, 10-13. Preconference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Minnesota Extension Service, University of Minnesota. Stahly, T.S. 1996. Impact of immune system activation on growth and optimal dietary regimens of pigs. In Recent Advances in Animal Nutrition, ed. P.C. Garnsworthy, J. Wiseman, and W. Haresign, 197-206. Nottingham University Press, Nottingham, United Kingdom. Underdahl, N.R. 1973. Specific Pathogen–free Swine. University of Nebraska Press, Lincoln. Wade, D. 1997. Nuts and bolts of multi-site production. Nuts and Bolts of SEW Multi-site Systems, 15-19. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Williams, N.H., T.S. Stahly, and D.R. Zimmerman. 1994. Impact of immune system activation on growth and amino acid needs of pigs from 6 to 114 kg body weight. Journal of Animal Science 72(supplement 2):57. Abstract. Zimmermann, W. 1990. Experiences in the EP sanitation programme to eradicate EP. Tierarztl Umschau 45:556-562.

36

2. Multi-site Rearing Systems

Multi-site rearing systems are defined as any pig production farm in which various stages of production or age groups are reared on separate sites and locations (loci). In general, multi-site rearing systems have most commonly been referred to by the following names: medicated early weaning (MEW), modified medicated early weaning (MMEW), isowean, segregated early weaning (SEW), age-segregated rearing (ASR), segregated disease control (SDC), traditional two-site, two-site isowean, three site, three-site isowean, multiple-site isowean, and multiple-source (two-site, three-site, multiple-site) isowean production. Some of these terms are synonyms. Multi-site isowean production refers to any multi-site system where pigs are weaned at a locus separate from the sows. Diagrams of these production systems are presented in this chapter. The reader may also want to review “Terminology” in Chapter 1 and the nomenclature, alphanumeric notation, and diagrams in Chapter 9.

One-site and Traditional Two-site Production Traditionally, farmers maintained their swine operations on one location, which is referred to as one-site production (Figure 2.1). All stages of production are on or surround the farmstead itself and are either in one building or in buildings separated by 10 to 20 yards. Alternatively, many farmers in the past began pork production with a few bred sows, reared the pigs to approximately 8 weeks of age, and then sold the “feeder pigs” to a neighbor with a grower/finisher building. This is commonly referred to as traditional two-site production (Figure 2.2), with the farrow-to-nursery buildings (stages of production 1 and 2) on one farm physically separated from the grower/finisher buildings (stage 3) on another farm. The grower/finisher could be owned either by someone else or by the owner of the farrow-to-nursery operation. When biosecurity measures (see Chapter 6, “Basic Essentials,” and Chapter 7, “Biosecurity”) are not adhered to for prevention of disease introduction, death loss and decreased pig performance occur, resulting in financial loss. Sometimes one-site and traditional two-site herds must be totally depopulated, the facilities cleaned and disinfected, and high–health status breeding stock procured. Some diseases can be eliminated from one-site and traditional two-site operations without depopulation by the use of all-in/allout pig flow (see Chapter 5, “Transmissible Gastroenteritis”). 37

Multi-site Pig Production

A. B.

Figure 2.1 One-site production. A. All stages of production are on one location. B. Five one-site farms of 1400 sows each in Weld County, Colorado.

38

2. Multi-site Rearing Systems

Figure 2.2 Traditional two-site production.

Table 2.1 Performance of Pigs in All-in/All-out and Continuous Flow Production. (Pigs from the Nursery of a Traditional Two-site Farm Reared in a Finisher.)

ADG (kg) Days to 105 kg Feed conversion

All-in/all-out

Continuous

.78 172 3.03

.69 185 3.22

Source: Scheidt et al., 1995.

Continuous versus All-in/All-out Pig Flow The pig flow in one-site and traditional two-site production is often continuous, meaning that the rooms, buildings, or loci are never empty of the various age groups of pigs. It has been recognized for many years (but not necessarily widely utilized) that all-in/all-out pig flow by room or building or loci is superior to continuous flow. Pigs reared in allin/all-out rooms or buildings or loci on one-site and traditional two-site farms have fewer cases of pneumonia and other diseases and have improved growth rates and feed efficiencies (Table 2.1). All-in/all-out pig flow lessens the economic impact of an infectious disease but does not eliminate the microbe causing the disease. Therefore, breeding stock suppliers with one-site and traditional two-site farms may find it necessary to totally 39

Multi-site Pig Production

depopulate for certain infectious agents, such as pseudorabies virus (PRV) and porcine reproductive and respiratory syndrome (PRRS) virus and toxigenic Pasteurella multocida.

Why Multi-site Isowean Production Systems? As discussed in Chapter 1, the incentive for constructing swine facilities on multiple sites via the Isowean Principle was to decrease the need for depopulating farms due to disease, especially for the production of breeding stock. After the development of medicated early weaning (MEW) and isowean (modified MEW) techniques (Figures 1.4 and 1.5), it became obvious that entire production systems needed to be built to utilize these concepts of infectious agent elimination. Soon after the construction of the first three-site (single source, single locus) system, producers of slaughter pigs also began constructing three-site (multi-source, multi-loci) systems due to economies of scale and the advantage obtained from improved growing-pig performance.

The Isowean Principle The Isowean Principle is based on the fact that piglets remain free from most of the serious potential pathogens endemic in a herd until weaning, and if reared separately from other age groups in the herd, they will remain free of the pathogens. It is the principle upon which multi-site rearing systems are based. The word isowean was derived from “isolated weaning,” which best describes the concept of separating the young suckling piglets at weaning from all other age groups of swine. The Isowean Principle was originally conceived for eliminating pathogens present in the breeding herd from being passed on to the growing pig (see Chapter 3, “Elimination of Infectious Agents by MEW and Isowean”). It was soon discovered; however, that an additional benefit was improved performance of isowean pigs compared to pigs weaned in close proximity to the other age groups on the farm (Figure 2.3). Isowean pigs reared to slaughter weight have less immune activation, an increased rate of gain, improved feed conversion, and more lean-gain than cohorts reared in close proximity to the other age groups (Chapter 4, “Pig Performance with Less Antigen Exposure via the Isowean Principle”). Isowean is synonymous with modified MEW, segregated early weaning (SEW), agesegregated rearing (ASR), and segregated disease control (SDC). Both modified MEW and SEW infer that early weaning is required, which definitely is not the case. The benefits of the Isowean Principle can be manifest in a range of weaning ages from 5 to 28 days.

Three-site Isowean Production In this type of multi-site design, the three stages of production— breeding production (stage 1), nursery production (stage 2), and finisher production (stage 3—are placed on

40

2. Multi-site Rearing Systems

Figure 2.3 Weights at days of age of isowean pigs and of littermate control pigs reared in the source herd.

Figure 2.4 Site 1 of a Gosper County, Nebraska, three-site system. The 2600 sows are housed in two farrow-to-wean facilities (breeding production stage).

three separate sites (Figures 1.3, 2.4, 2.5, and 2.6). Three-site isowean production systems were originally designed to produce breeding stock free of pseudorabies (Aujeszky’s disease) virus (PRV). It is possible for the adults in stage 1 infected with PRV to produce piglets that are free of the virus at weaning (see Chapter 5, “Pseudorabies” [Aujeszky’s disease]). All-in/all-out pig flow is practiced by room in stage 1. Depending on the size of the breeding herd, all-in/all-out pig flow by room or building can be practiced in stages 2 and 3.

41

Multi-site Pig Production

Figure 2.5 Site 2 of the Gosper County, Nebraska, three-site system. Three prenursery and three nursery buildings hold about 8000 pigs ranging in age from 3 to 8 weeks (nursery production stage).

Figure 2.6 Site 3 of the Gosper County, Nebraska, three-site system. Five grower and 14 finisher buildings hold over 20,000 head of pigs until they are sold as breeding stock or sent to slaughter (finish production stage).

Expansion of Existing One-site and Traditional Two-site Production Systems After construction of the first three-site (single source, single locus) system in 1988, it was recognized that existing operations could be expanded and renovated using the Isowean Principle. For example, a 150-sow one-site farrow to one-half finish operation can be readily expanded to a 250-sow three-site isowean system (Figure 2.7). The original farrow to one-half finish site becomes stage 1; the nursery facilities can be converted to farrowing rooms and the finisher can house gestating sows. The weaned pigs are placed on a newly constructed, leased, or contracted nursery (site 2) and finisher (site 3). Traditional two-site systems are easily expanded, as shown in Figure 2.8.

42

2. Multi-site Rearing Systems

Figure 2.7 Conversion of a one-site farrow to one-half finish operation to a three-site isowean system.

This conversion to three-site production allows the breeding herd to be expanded without necessitating depopulation for disease elimination. In addition, more pigs are produced at a higher level of health status, which results in improved rates of gain and feed conversion.

Three-site (Multi-source, Multi-loci) Isowean Production These systems often contain over 5000 sows in stage 1. All-in/all-out pig flow is practiced by site for stages 2 and 3. Each week’s group of weaned pigs fills a nursery building located on an isolated site on an all-in/all-out by locus basis. Each week’s emptying of a nursery site (usually 7 weeks after filling) is placed in a finisher building located on an isolated site (Figures 2.9 and 2.10). Pigs flow from nurseries to finishers on an all-in/all-out by locus basis. There are eight nursery loci in Figure 2.9; the eight finisher loci can have one or more buildings per locus. The disadvantage of this system is the large number of sows required to justify the cost of isolated all-in/all-out nursery and finisher sites. However, the system is particularly well suited for both large-scale breeding stock production and slaughter-pig production via contracted nursery and finisher buildings. When the breeding herd (stage 1) is placed on more than one locus, the weaned pigs originate from more than one source (or stage 1 location). Since the emergence of the PRRS virus, multiple sourcing of isowean pigs has become an important distinction in defining the nature of various multi-site production systems. Single-source isowean pigs have better production performance than pigs originating from multiple sources (Tables 2.2 and 2.3). A variety of infectious agents can be excluded by the Isowean

43

Multi-site Pig Production

A. B.

Figure 2.8 Conversion of a traditional two-site operation to a three-site system. A. Traditional two-site operation with one-half finishing at a separate location and one-fifth finishing at the same location as the breeding production and nursery production stages. B. Three-site isowean system. An isolated nursery and an isolated finisher for one-half capacity were newly constructed.

44

2. Multi-site Rearing Systems

Figure 2.9 Three-site (single-source, multi-loci) production.

Principle when pigs originate from either single- or multi-source stage 1 production sites (see Chapter 3, “Exclusion of Specific Agents by MEW or Isowean”). Figure 2.11 illustrates a three-site (multi-source, single locus) system. Stage 1 production occurs in more than one locus. Nurseries are in one locus with one or more buildings. Finishers are in a third locus with one or more buildings. Figure 2.12 illustrates a three-site (multi-source, multi-loci) system. Stage 1 production occurs in more than one location. Each batch of weaned pigs is placed in one or more allin/all-out buildings in an isolated locus. The pigs at each nursery locus are subsequently placed in one or more all-in/all-out buildings in an isolated locus. Nursery and finisher loci are all-in/all-out by locus.

Two-site Isowean Production In a two-site isowean system, stage 1 production usually is at one locus and stages 2 and 3 are on another isolated locus. The nursery and finisher buildings usually contain rooms with all-in/all-out throughput. The nursery and finisher buildings commonly are separated from one another but are on the same locus. Beginning in 1990, the late Al Leman of Webster City, Iowa, encouraged many midwestern U.S. pork producers to modify existing father and son/daughter operations to convert existing family farms to this system.

45

Multi-site Pig Production

Figure 2.10 Aerial photograph of a PIC Cochino nursery complex in Oklahoma. The nurseries are on eight separate loci consisting of four buildings per locus. The isowean pigs originate from four 3600-sow site 1 loci.

Table 2.2 Performance of Pigs in a Stage 2 Nursery of a Three-site System. (Pigs from Either a Single-source Stage 1 Locus or Multi-source Stage 1 Loci.) Performance

ADG Mortality

Single Source

Multi-source

387 g/d 1.63%

325 g/d 4.03%

Source: Adapted from Godbout et al., 1996.

Table 2.3 Performance of Pigs in a Stage 3 Finisher of a Three-site System. (Pigs from Either a Single-source Stage 1 Locus or Multi-source Stage 1 Loci.) Performance

Single Source

Multi-source

P

ADG Feed conversion Mortality

837 g/d 2.62 kg/kg 0.92%

776 g/d 2.81 kg/kg 2.68%

<0.01 <0.01 <0.01

Source: Adapted from Godbout et al., 1996.

46

2. Multi-site Rearing Systems

Figure 2.11 Three-site (multi-source, single-locus) production.

Figure 2.12 Three-site (multi-source, multi-loci) production.

The Two-farmstead Conversion Family farmers in north central Iowa first developed two-site isowean systems. Usually two farmsteads of father and son/daughter operations were consolidated from two farrowing locations to one stage 1 production site. The other farmstead, converted to contain stages 2 and 3, consists of a nursery building separated from the finisher building. The nursery at site 1 was expanded to become a farrowing room or building. The 47

Multi-site Pig Production

Figure 2.13 Two-site isowean production. Beginning in 1990, the late Al Leman of Webster City, Iowa, encouraged many midwestern U.S. pork producers to modify existing father and son/daughter operations to convert existing family farms to this system.

farrowing room or building at site 2 was converted into a nursery (Figure 2.13). Subsequently, new systems were built using this same concept.

Large Two-site Isowean Systems In order to decrease capital and operating costs, some large corporate producers have built multiple-source two-site isowean systems (Figure 2.14). Stage 1 production is at more than one loci. Stages 2 and 3 are located on isolated loci with one nursery and two finisher buildings per locus. Each batch of weaned pigs is placed in an all-in/all-out nursery building. Every 8 weeks a nursery is emptied into one all-in/all-out finisher building per locus. Every 16 weeks a finisher is emptied. Only four loci are required. Capital costs are decreased due to fewer site locations and transport vehicles (and manure storage systems unless deep pits are used under buildings). Operating costs are decreased due to fewer times the pigs need to be transported. An additional benefit is the ability to maintain pen integrity when moving pigs from the nursery to the finisher building. The two-site systems illustrated in Figures 2.13 and 2.14 are not recommended for the production of breeding stock because total depopulation of site 2 is necessary in most instances to eliminate most infectious agents should the site become contaminated.

Two-site Isowean On-site Production This system is a modification of traditional two-site production in which stage 2 pigs are placed in a nursery at site 1 but are separated from stage 1 production by several hundred 48

2. Multi-site Rearing Systems

Figure 2.14 Two-site isowean (multi-source, multi-loci) production.

Figure 2.15 Two-site isowean on-site production.

feet (usually across the waste-storage or freshwater lagoon). Stage 3 production is located at an isolated finisher site or sites (Figure 2.15). The best designs have separate air- and waste-handling systems in each all-in/all-out room of the nursery. The pigs in each nursery room are placed in all-in/all-out isolated finisher buildings. In the early 1990s, Dr. Paul Armbrecht of Lake City, Iowa, suggested this system to Land-O-Lakes for farms with approximately 2000 sows. 49

Multi-site Pig Production

NurFin Isowean Production NurFin isowean production combines the advantages of three-site (multi-loci) and twosite isowean production (Figure 2.16). In this system, stages 2 and 3 are located in one nursery/finish (NurFin) building, with pig flow being all-in/all-out by building or locus (Figure 2.17). During the stage 2 nursery period the weaned pigs are housed in either one end or the center (Figure 2.18) of the NurFin (wean-to-finish) building in a portion of the same space that later will be used to grow the pigs to slaughter weight. Additional heat, special drinkers for water, and temporary flooring (comfort boards) are required for the first few weeks after introduction of pigs into a NurFin building. Beginning in the mid-1990s, Dr. Joe Connor of Carthage, Illinois, encouraged many midwestern pork producers to expand their operations with this type of building. For some production systems NurFin isowean is the ideal approach and is well suited to both breeding stock and slaughter-pig production. The major disadvantage is that not all of the floor space is utilized when the NurFin building is used for the nursery phase. The efficiencies gained in transport, management, and manure handling may outweigh this economic disadvantage.

Figure 2.16 NurFin (wean-to-finish) isowean production.

50

2. Multi-site Rearing Systems

Figure 2.17 Aerial photograph of Carroll Farm near Carthage, Illinois. The 900sow site 1 with the breeding production stage is on the left, and four NurFin buildings with a capacity of 1000 head each on two loci are on the right.

A. B.

Figure 2.18 Farmweld Millennium Design NurFin (wean-to-finish) building. A. In the “wean position,” the pigs are penned in the center of the building and there is an alleyway along one outside wall. B. In the “finish position” for larger hogs, the gates are reconfigured to create a center hallway and allow full utilization of space. (Design kindly supplied by Farmweld, Inc., Teutopolis, Illinois.)

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Multi-site Pig Production

Outdoor Isowean Pig Production A portion of the pigs in the world likely always will be reared outdoors rather than being confined in buildings. In fact, one could argue that pigs reared outdoors are actually being produced in a multi-site system. Near Watlington in Oxfordshire, England, Mr. Richard Roadnight developed an extensive large-scale outdoor system of production in the 1950s. Stage 1 production occurs in an extensive pasture system with weekly farrowings year-round. After weaning, pigs are usually reared in confinement buildings. Nursery and finisher buildings are placed in isolated locations. If these buildings are kept well isolated from the breeding and farrowing stage 1 herd, then the advantages of isowean can be realized (Figure 2.19). In fact, I conceived the idea

Figure 2.19 Outdoor isowean production.

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2. Multi-site Rearing Systems

of three-site production in 1985 while my wife and I were farming a 150-sow farrow to one-half finish outdoor system near Rothville, Missouri.

Super Isowean Nurseries The number of pigs weaned in any given week may vary considerably, even on wellmanaged operations. Overproduction can result in crowding and stress, which reduce performance in the nurseries. The problem can be particularly severe on continuousflow one-site farms. Many producers with one-site and traditional two-site farms have found that weaning the poorest and lightest weight pigs into off-locus isolated nurseries to be quite beneficial. In addition, large corporate operations with multisite systems have built additional super nursery accommodations for periods of overproduction.

F10 Production Kirk Schuiteman helped farmers in Iowa set up systems in which the sows were removed from the farrowing crates and the piglets remained in the pens until 10 weeks of age. Marie-Claude Poulin subsequently showed that the performance of F10 pigs was similar to that of isowean pigs. Interestingly, in her studies, the F10 pigs became infected with Mycoplasma hyopneumoniae, but the isowean pigs did not. The specific stress-free systems used in the Netherlands and Denmark are somewhat similar to F10. In the Netherlands, the system is referred to as KOH production.

All-in/All-out Separation of Nursery and Finish by Pen, Room, Building, Locus, or Site Multi-site rearing systems require all-in/all-out pig flow, or throughput, rather than continuous flow (F in Figure 2.20), for transfer between facilities and overall production management. The first three-site systems were constructed with all-in/all-out nursery rooms in one building on site 2 with one locus (E) and with all-in/all-out finisher buildings on site 3 with one locus (D). The concept of three-site (multi-loci) production allows for the all-in/all-out pig flow on each locus within a site with one or more buildings per locus (A). The six types of all-in/all-out and continuous pig flow illustrated in Figure 2.20 are found either alone or in combination with the various rearing system designs discussed in this chapter. The type of pig flow design is often dictated by the size (including the number of sows in stage 1 production) of the production system.

Summary A variety of methods referred to as multi-site pig production utilize the Isowean Principle to achieve either freedom from or a reduced level of infectious agents in weaned pigs. The 53

Multi-site Pig Production

Figure 2.20 Production throughput by pen, room, building, or locus. (Modified from Gadd, 1997; Evans, 1997)

objective for the commercial producer of slaughter pigs is to raise pigs that have less mortality, improved feed conversion and rate of gain, and high lean tissue. In commercial production, the presence or absence of infectious agents is not important if the performance of the pigs is excellent. By contrast, the breeder must produce growing pigs free from certain infectious agents when utilizing the Isowean Principle of production. There are many possible designs and configurations for multi-site isowean production systems. Important features all these systems have in common are: • Three stages of production defined as the breeding production stage (stage 1), the nursery production stage (stage 2), and the finisher production stage (stage 3). The three stages are separated in three-site systems, but in two-site isowean or NurFin isowean systems stages 2 and 3 are both at site 2 and within single or multiple loci. In a three-site system, each week’s production of weaned pigs is placed in either single or multiple loci at sites 2 and 3. • Weaned pigs originating from either a single source or multiple sources in all types of multi-site production. • Strict all-in/all-out pig movement, either by room or building, with a very narrow range in ages for each weaning group (preferably 2–3 days and definitely less than 7 days). 54

2. Multi-site Rearing Systems

• Separation by more than a mile, if possible, of the various sites and loci for breeding stock production. • Separate air- and manure-handling systems for each room in a building (nursery or finisher) that houses different age groups of pigs. A recent development in the United States for two-site isowean production is NurFin isowean production, which utilizes wean-to-finish buildings. The weaned pigs are placed in one building and reared in the same building until slaughter weight. Use of the Isowean Principle applies well to expansion of existing herds without the need for depopulation, since one-site farrow-to-finish herds (containing all three stages of production) can be readily modified to two- or three-site isowean production. In herds expanded in this manner, the original site is converted to stage 1 production and the number of sows is increased, and new or used facilities on site 2 house stages 2 and 3.

Bibliography Alexander, T. J. L., and D. L. Harris. 1992. Methods of disease control. In Diseases of Swine, 7th ed., ed. A. D. Leman, B. E. Straw, W. L. Mengeling, S. D’Allaire, and D. J. Taylor, 808–836. Iowa State University Press, Ames, Iowa. Alexander, T. J. L., K. Thornton, G. Boon, R. J. Lysons, and A. F. Gush. 1980. Medicated early weaning to obtain pigs free from pathogens endemic in the herd of origin. Veterinary Record 106:114–119. Brummer, F. 1998. The quest for the perfect wean-to-finish building. Nuts and Bolts of SEW Multisite Systems, 223–227. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Connor, J. 1994. New innovations in building design: Wean-to-finish. Unpublished presentation at the annual meeting of the American Association of Swine Practitioners, Chicago, Illinois. Ekkel, D. 1996. Impact of farrow-to-finish production on health and welfare of pigs. Ph.D. thesis, Faculty of Veterinary Medicine, Utrech University, the Netherlands. Evans, M. 1997. Personal communication. Gadd, J. 1997. The segregation aspects of segregated early weaning. Animal Talk 4 (No. 9), Nottingham Nutrition International newsletter, United Kingdom. Godbout, D., M. Bonneau, D. Boyaud, B. Couture, and G. P. Martineu. 1996. Segregated early weaning: Impact of number of sources of piglets on growth performances in nursery and growing/finishing. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 479. Harris, D. L. 1988a. Alternative approaches to eliminating endemic diseases and improving performance of pigs. Veterinary Record 123:422–423. Harris, D. L. 1988b. New approaches to elimination of infectious diseases from swine. Proceedings of the 92nd Annual Meeting of the U.S. Animal Health Association, Little Rock, Arkansas, 416–426. Harris, D. L. 1990a. The use of isowean three-site production to upgrade health status. Proceedings of the 11th International Pig Veterinary Society Congress, Lausanne, Switzerland, 374. Harris, D. L. 1990b. Isolated weaning—Eliminating endemic disease and improving performance. Large Animal Veterinarian, 10–12. Harris, D. L. 1992. Multiple-site production. Proceedings of the South East Veterinary Conference, Raleigh, North Carolina, 1–10.

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Hill, H. 1997. Single sourcing versus multiple sourcing in multi-site production systems. Nuts and Bolts of SEW Multi-site Systems, 3–9. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Poulin, M. C., B. Couture, and B. W. Wiseman. 1993. Early weaning effects on growth. Allen D. Leman Swine Conference. Vol. 20. 1993, 205–210. Veterinary Outreach Programs, University of Minnesota, St. Paul. Scheidt, A. B., T. R. Cline, K. Clark, V. B. Mayrose, W. G. Van Alstine, M. A. Diekman, and W. L. Singleton. 1995. The effect of all-in/all-out growing/finishing on the health of pigs. Swine Health and Production 3(5):202–205. Schinckel, A. P., L. K. Clark, A. L. Grant, G. G. Stevenson, and J. J. Turek. 1996. Evaluation of the effects of immune system activation versus disease on pig growth. Allen D. Leman Swine Conference. Vol. 23. 1996, 107–112. Veterinary Outreach Programs, University of Minnesota, St. Paul. Schuiteman, K. D. 1992. Using pig flow to eliminate diseases. Allen D. Leman Swine Conference. Vol. 19. 1992, 163–169. Veterinary Outreach Programs, University of Minnesota, St. Paul. Stahly, T. S. 1996. Impact of immune system activation on growth and optimal dietary regimens of pigs. In Recent Advances in Animal Nutrition, ed. P. C. Garnsworthy, J. Wiseman, and W. Haresign, 197–206. Nottingham University Press, Nottingham, United Kingdom. Thornton, K. 1990. Outdoor Pig Production. Farming Press Books, Ipswich, United Kingdom. Tielen, M. J. M. 1974. Incidence and the prevention by animal care of lung and liver infections in fattening pigs. Ph.D. thesis, Agricultural University of Wageningen, the Netherlands.

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Multi-site rearing systems utilize the Isowean Principle to exclude microbes that cause disease. When disease-causing microbes are prevented from inhabiting the pre-weaned pig and thus are excluded from the growing pig, pigs perform better, have leaner carcasses, and are more profitable. Other methods of exclusion, such as surgical derivation, have been developed, but they are not as practical as multi-site isowean rearing systems. Some microbes can be eliminated from pigs by certain management procedures, including medication, sanitation, and enhanced immunity due to aging, decreased stocking density, and/or vaccination. Multi-site isowean rearing systems are particularly useful in this regard because the young growing pigs are separated from the adult breeding herd. In this way, there may be less exposure of the site 1 animals to the microbe and thus it may be more readily eliminated from the older pigs in the farm. The Isowean Principle is a sophisticated technique. Strict adherence to disease control, biosecurity, and management practices is essential during the nursery and finisher stages of production (Chapter 6, “Basic Essentials,” and Chapter 7, “Biosecurity”). Its successful implementation in multi-site rearing systems requires an understanding of microbe/pig interaction by all levels of the management and production teams. The emphasis in this chapter is on excluding and eliminating microbes by medicated early weaning (MEW) and isowean. The advantages of multi-site isowean rearing systems for eliminating infectious agents from adults in a site 1 population are included. Fundamental aspects of microbe/pig interaction and other methods of microbe exclusion and elimination also are discussed.

Microbes and Disease Microbes are microscopic in size and may or may not cause disease. Disease (from “dis” “ease”) is any abnormal state detrimental to the pig. Viruses, bacteria, mycoplasmas, and some forms of parasites can cause disease and are considered microbes. When a microbe contributes to the occurrence of disease, it is often referred to as a pathogen. A normal flora of microbes covers literally every external and internal surface of the pig’s body. These normal microbes occur on the skin, in the ears, mouth, stomach, intestine, bladder, and vagina of the pig. The feces are composed primarily of microbes, approximately 57

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100 billion microbes (1011 logs) per gram. The pig is exposed to far more helpful microbes than to harmful pathogens when reared under reasonable levels of sanitation either extensively outdoors or in confinement buildings. The helpful or good microbes produce nutrients and aid digestion of food. Whether or not disease occurs in pigs depends on the specific causal agent or agents (often microbes), host factors, and environmental factors. These determinants are variable and directly or indirectly influence the frequency and/or occurrence of disease. The presence of a pathogen on or in the pig’s body may or may not result in disease. When a pathogen is detected as being present in or on the pig, it is often referred to as an infection. A pig can be infected with a pathogenic microbe but show no disease or illness. Usually the pig produces antibodies in its blood after being infected with a pathogen. These antibodies may be detected and quantitated in laboratory serologic tests (see Chapter 4, “Antigens, Antibodies, and Immunity”). The presence of antibodies to a pathogen does not necessarily mean that disease is occurring or that the pathogen is still residing in or infecting the pig. Several situations are possible regarding an infection with a pathogen: 1. The pig could be in the incubatory stages of disease (an infection exists but disease has not yet occurred). 2. A disease or illness is occurring. 3. The pig has recovered from the disease on its own or because of treatment but is still infected with the pathogen (this situation is often referred to as a carrier state). The carrier pig may or may not be shedding the pathogen. Thus, a carrier pig may or may not be infecting other pigs. 4. The pig can be “immune” to the effects of the disease but still be infected with the pathogen. This immune state can be induced by vaccination or simply by recovery from the infection. 5. The pig can recover and eliminate the pathogen. Before the discovery of the Isowean Principle, exclusion of most pathogenic microbes could only be accomplished by separating piglets from their mothers at birth. Some pathogenic microbes can be excluded and/or eliminated by multi-site isowean production, while the levels of other microbes (both good and pathogenic ones) and their toxins are simply reduced. Just how this takes place is the main topic of this chapter.

Origin of Microbes for the Newborn Piglet Usually, piglets are sterile or microbe-free in the uterus of the dam. Some infectious microbes, such as the porcine reproductive and respiratory (PRRS) virus, can infect piglets in utero. The most common first exposure of the piglet to microbes comes as it passes through the cervix into the vagina of its mother. As naturally farrowed pigs pass through the vagina, they become infected with microbes. When the piglet is born, more microbial exposure occurs from its contact with feces, the skin of the dam, and the swine58

3. Exclusion and Elimination of Microbes

rearing facility. Some microbes grow on the skin; others are swallowed by the piglet and begin to establish themselves in its mouth, stomach, and intestines. Whether the piglet becomes diseased due to exposure to these microbes depends on the health and immune status of the sow, the overall sanitation of the farrowing facility, colostrum and milk intake, and the comfort level (stress, temperature, dampness, etc.) of the pig-rearing environment. Medicated early weaning and isowean are two of four methods that can be utilized to alter the establishment of the microbial flora of the newborn piglet.

Altering the Microbial Flora of the Newborn Piglet Hysterectomy-derivation, Colostrum-deprivation (HDCD) Germ-free (microbe-free) pigs can be procured surgically by opening the uterus and extracting the pigs by hysterectomy under aseptic conditions. This is the basis for deriving specific pathogen–free (SPF) pigs that are then reared in isolation and either are given artificial milk replacer or are cross-fostered onto surrogate nurse sows. These pigs develop an isolator microbial flora present in the environment. Pigs reared on milk replacer without colostrum are often referred to as hysterectomy-derived (or caesarian-derived), colostrumdeprived (HDCD or CDCD) pigs. It should be noted that occasionally piglets might be infected in utero, particularly with viral agents. If this is the case and if the piglets don’t receive colostrum, it is likely they will die soon after surgery. Therefore, care must be taken that each HDCD litter is kept isolated from other pigs prior to being exposed to other surgically derived litters or being introduced into a herd. High–health status herds established by using HDCD procedures combined with milkreplacer diets are considered primary SPF herds. When one-site and traditional two-site farms are established as primary SPF herds and maintain proper SPF techniques, infectious disease levels can be low and pig performance can be excellent. However, eventually breakdowns of disease will occur and performance can deteriorate, especially in the growing pigs (Figure 3.1). The rate of deterioration depends on many factors, including biosecurity and source of replacement breeding stock. Even pigs in recently derived SPF herds of high–health status have lower performance if they remain in the farm than do isoweanderived pigs from the same facility (Figure 3.2). Deterioration in performance is economically important since over 60% of operating costs is the feed for growing pigs. Death loss (mortality rates) can also increase as the health status of herds decrease.

Snatch Farrowing (SF) Doug Ross and Ross Cutler developed “snatch farrowing” to avoid deriving pigs surgically. Snatch-farrowed (SF) pigs are collected directly from the vagina at birth. When done properly, these pigs differ from HDCD pigs only in their exposure to vaginal microbial flora. These pigs are reared in isolation and either are given milk replacer or are crossfostered onto surrogate nurse sows. 59

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Figure 3.1 Degradation of the health status of pigs over time.

Figure 3.2 Performance of littermate pigs weaned under three conditions. Control: weaned at 21 days of age into a continuous flow nursery on the farm of origin. On-site: weaned at 12 days of age into an all-in/all-out nursery on the farm of origin. Off-site: weaned at 12 days of age into an all-in/all-out nursery isolated (isowean) from the farm of origin. (Modified from Patience, 1997)

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Medicated Early Weaning Tom Alexander developed medicated early weaning (MEW) as an alternative to surgical derivation for the production of SPF pigs. The technique has the distinct advantage of avoiding surgery on the donor sow. In MEW, small groups of pregnant near-term sows from one or more farms are placed in strict isolation for farrowing (see Figure 1.4). Ideally, each isolated group of sows is induced to farrow within 2 to 4 days of one another. The sows are heavily medicated both prior to and during their stay in the farrowing unit. To assure elimination of some infectious microbes, the sows can only be from second or higher parities to increase the levels of colostral and milk immunity (see Chapter 4, “Piglet and Sow Immunities”). Vaccines can be administered to the sows 4 to 6 weeks prior to farrowing to further increase these levels. Immediately after birth, the piglets are administered heavy doses of antimicrobials to lessen the chance of sow-to-pig transfer of microbes. The piglets are weaned at 5 or fewer days of age into isolated nurseries well away from the farrowing unit. The piglets often continue to be medicated for several weeks after weaning. For best results, each weaning group should be only 1 to 2 days different in age when it is placed into an all-in/all-out nursery accommodation. Subsequently, the pigs are moved to a growing and finishing unit that is well isolated from the farrowing and nursery units.

Isowean Isowean has some synonyms: modified medicated early weaning (MMEW), segregated early weaning (SEW), age-segregated weaning, and segregated disease control (SDC). The word isowean, derived from the words “isolated weaning,” more accurately describes the basis of the Isowean Principle as defined in Chapter 2 (“Isowean Principle”). The Isowean Principle denotes pigs that are weaned away from and in strict isolation from the other age groups of pigs in a multi-site rearing system. Isowean is different from MEW because in isowean the sows are not removed from the farm and placed in isolation to farrow (Figure 1.5). Also, isowean pigs are usually weaned at an older age than are MEW pigs. The weaning age of an isowean pig can vary from 8 days to 4 weeks of age, depending on the microbial agents to be eliminated. However, as in MEW, the range in age of any one farrowing group should be very narrow. In practice, it should be only 2–5 days. In isowean, the pregnant sows are farrowed in the source farms and are not moved to isolation facilities. Usually the sows are vaccinated in late gestation, as in MEW, but often they are not medicated. It is highly recommended that the sows be placed in an all-in/allout farrowing room and that all sows in the room are farrowed within a 4–7 day period. If bacterial or mycoplasmal microbes are to be eliminated, the piglets are usually medicated during the suckling and post-weaning periods. At weaning, the piglets are moved to an isolated nursery and placed in an all-in/all-out room or building. As in MEW, each weaning age group of isowean pigs is placed in an

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Table 3.1 Infectious Agents Eliminated by Isowean Medications Organism

Haemophilus parasuis Bordetella bronchiseptica Pasteurella multocida (toxigenic) Actinobacillus pleuropneumoniae Mycoplasma hyopneumoniae Salmonella spp. Lawsonia intracellularis Leptospira spp. PRV SI virus PRRS virus TGE virus

Maximum Age of Weaning

Vaccines

Sows

Piglets

Sows

Piglets

10 10

–a –

+b +b

+ +

– –

8–10 21–28 20 14–16 10 14–16 20 20 14–16 20

– – –

+b + +b

+ + +

– – –

– – – – – –

– + – – – –

– + + +c – +c

– – – – – –

Source: Harris and Alexander, 1999 a (–) denotes medication and vaccine not necessary; (+) denotes medication and vaccines may be required. b Medication a definite requirement, particularly as weaning age increases. c Vaccines may not be necessary.

isolated grower/finisher away from the isolated nursery and the source farm containing the mature swine. Table 3.1 lists weaning ages, and antimicrobial and vaccine strategies used to produce batches of isowean pigs. Whether or not antimicrobials are used depends on which infectious agents present in the source farms are to be eliminated. If only viral agents are to be eliminated, antimicrobials may not be necessary.

Comparison of HDCD, SF, MEW, and Isowean Pigs All four procedures are useful for procuring batches of pigs free of or with reduced levels of microbial pathogens. Table 3.2 shows the relative elimination efficacy of the procedures. Isowean is by far the most economical, but it is not as efficacious as MEW, except for the elimination of Streptococcus suis. Medicated early weaning is highly efficacious but not as reliable as HDCD and SF methods. Isowean and MEW pigs are easier to procure in large batches than are HDCD and SF pigs. All four procedures will not eliminate a microbial pathogen that is passed transplacentally from the dam to the piglet in utero. For this reason, it is imperative that pigs derived by any of these methods be placed in isolation or evaluated prior to directly introducing them into a herd as replacement breeding stock. If HDCD or SF pigs are to be crossfostered, the surrogate nurse sows should be placed in isolation outside the recipient herd for 2–3 weeks to allow time for evaluation of any transplacental infection. Piglets born to the surrogate mothers can be used as sentinel pigs as well. 62

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Table 3.2 Efficacy of Eradication Methods Used to Produce Disease-free Groups or Batches of Pigs for Stocking New or Depopulated Premises Agent

Surgical Derivation

Snatch Farrowing

MEW

Isowean

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae PRV (Aujeszky’s virus) TGE virus PRRS virus* Serpulina hyodysenteriae Salmonella spp. Streptococcus suis type 2 Haemophilus parasuis Bordetella bronchiseptica Parvovirus Influenza virus Leptospira spp. Eradication very likely Eradication likely but not always Eradication not likely *See Table 5.1

MEW or isowean piglets have a greater chance of being contaminated with an unwanted microbial pathogen during lactation than do HDCD or SF piglets. Experience has shown that a high percentage of MEW and isowean groups are negative for most pathogens. Still, it is important that each weaning group be reared in isolation from other weaning groups in case a microbial pathogen should infect a group of piglets. It is imperative that pigs are isolated from the other age groups on a recipient farm for several weeks prior to entry into the main farm. In some cases, it is advised that sentinel pigs be reared with the MEW or isowean pigs. The sentinel pigs would need to be from a source free of the specific infectious agents that are being eliminated by MEW or isowean. MEW and isowean piglets absorb antibodies from colostrum during the first 36 hours of life. The passively acquired antibody is slowly removed from the body; the half-life is approximately 21 days. Since MEW and isowean piglets have passive antibodies, it is more difficult to know, based on serologic tests, when an unwanted microbial pathogen has contaminated a weaning group. The piglet cannot be infected with a pathogen but contain antibodies in its serum to the pathogen received via the colostrum (see Chapter 4, “Immune Status of the Dam”). Again, sentinel pigs are useful in this regard. Alternatively, the decay in serum antibody can be plotted over time and can give an indication of whether the piglet has become infected during the suckling period with an unwanted microbial pathogen (Figure 3.3).

Elimination of Infectious Agents by MEW and Isowean Many factors are involved in creating a MEW or isowean pig free of infectious agents present in its mother or the pig-rearing environment. The factors include the level of 63

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Figure 3.3 Decline curve for maternal antibodies in naturally farrowed piglets. (Modified from Haye and Kornegay, 1979)

immunity in the dam to the infectious agent(s); the level of immunity passively acquired by the piglet either via the colostrum or the milk; the age of piglet at which colonization of a potential pathogen occurs; the medications given to the dam and/or the piglet; and the overall throughput, sanitation, and biosecurity practices on the farm. Table 3.3 summarizes the current state of knowledge concerning these factors for the important microbial pathogens of pigs.

Sow and Piglet Immunities If the dam has been previously infected with a microbial pathogen, it is likely that antibodies will be present in her colostrum and milk and that they could aid in protecting the suckling piglet against infection. However, if the dam has never been infected and the microbial pathogen is present in the pig-rearing environment (perhaps due to infection of another sow in the farrowing room), piglets nursing non-immune sows will become infected. The degree of immunity in sows varies, depending on parity, type of rearing system, presence or absence of the infectious agent in the various stages of production, and the nature of the infectious agent. In general, first-parity sows and sometimes late-parity sows can have low immunity or no immunity to a pathogen. One-site and traditional two-site farms will tend to have higher levels of sow immunity because housing various age groups of swine in the same airspace or in close proximity results in greater transmission and infection rates of pathogens. (See Chapter 4 for a detailed discussion of sow, piglet, and herd immunities.) The level of sow immunity can be enhanced by intentional exposure to infectious agents during acclimatization of replacement gilts, prior to breeding all sows, and 3–4 weeks prior 64

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to farrowing (see Chapter 7, “Gilt Development”). Some vaccines also will enhance sow immunity and aid in the protection of piglets against infection during suckling. Piglets must receive colostrum within 36 hours of birth in order to absorb protective factors (primarily antibodies). After 36 hours, the piglet’s gut closes and these colostral antibodies are no longer absorbed into the blood. The presence of antibodies in the blood is important for protection against certain types of infectious agents, such as Streptococcus suis, Haemophilus parasuis, and Erysipelothrix rhusiopathiae. Both colostrum and milk contain antibodies that also help protect the piglet against some enteric infections by coating the mouth, tonsils, stomach, and small and large intestine. Piglet immunity can be enhanced by inducing the pig to produce its own antibodies via vaccination or by intentional exposure to an infectious agent (see Chapter 4, “Piglet and Sow Immunities”).

Age Variation of Piglets in the Farrowing Room Ideally, each pig in a farrowing room should be of identical age. In practice, this is difficult to achieve, but in the original MEW experiments, sows were farrowed in isolated farrowing rooms within a 24-hour period. A variation in the age of piglets in the farrowing room could result in a wide variation in the age at weaning, which increases the possibility of lower immunity levels and increases the chance of infection in the oldest pigs in the weaned group.

Weaning Age The age of the piglet at weaning (and the length of lactation) can be critical to successful elimination of some infectious agents (Tables 3.1 and 3.3). In general, the younger the weaning age, the more likely the piglet will be weaned free of infectious agents. If a very high level of immunity can be created and maintained in the sows, the weaning age required to eliminate a pathogen may increase.

Medications Administering medications to both sows and piglets may help prevent colonization of piglets by most bacterial agents (not viruses). Medications to sows can be given via the feed or water or by injection. Piglets must receive medications by oral dosing or injection. Oral dosing can require 2–3 administrations every 24-hour period. Injectable antibiotics can need to be given every 12 hours or as infrequently as every 3–6 days, depending the pathogens involved and on the antibiotics used. Administering medications (particularly to piglets) can increase the weaning age required to eliminate a pathogen.

Sanitation Overall sanitation of the farrowing room environment will determine the levels of infectious agent exposure to the young piglet. If there is a very high level of infectious agents on floor surfaces, feeding areas, and in the air, the piglet can become infected more readily and at a younger age. All-in/all-out throughput combined with proper cleaning and disinfection is essential for minimizing the level of infectious agents in the overall pigrearing environment. 65

2–5 weeks (May prevent lesions but not infection. Sow vaccination may decrease colonization but still get clinical disease) Several weeks (Yes, antisera too)

2 days

<5 days

Suckling

7 days

12 weeks In utero?

Actinobacillus suis

Bordetella bronchiseptica

Erysipelothrix rhusiopathiae

Haemophilus parasuis

Lawsonia intracellulare Leptospira spp. (Yes)

2–4 weeks (Yes)

ELISA 28–30 d Neutralization/CF 20–21 days (PC Fenwick) (Probably not against all types) ?

<11 days

Actinobacillus pleuropneumoniae

Organism

Earliest Recorded Age of Detection

Duration of Colostral Immunity from Exposed Sows (Is colostral immunity protective against colonization?)

Table 3.3 Characteristics of Important Pathogens of Pigs

Pig-to-pig Ingestion Skin wounds Aerosol Direct contact Fecal Feces Via contact with mucous membranes Venereal Transplacental Via milk experimentally Mammals, birds, insects?

6–20 weeks Breeding stock

2 weeks to 4 months

About 5 days 1–4 weeks

Rodents, dogs, horses, hedgehogs, raccoons, skunks, opposums

Direct contact Fecal-oral Aerosol Dam-to-pig Most domestic and wild animals, rodents

24 hours

Carrier pigs

?

Days

All ages; usually suckling and recently weaned Atrophic rhinitis: 4–12 weeks Pneumonia: 3–4 days to weaning

Usually 3 months to 3 years of age

Aerosol Direct contact

Flies

Hours variable

Mode of Transmission

All ages; usually growing/finishing pigs

Other Reservoirs

Incubation Period for Disease

Age When Clinical Signs Are Usually Seen

Suckling pigs

4 days

Day 0

Day 0

<1 day

<1 day

Serpulina hyodysenteriae

Staphylococcus hyicus

Streptococcus suis

PRRS virus

Pseudorabies virus

TGE virus

Source: Modified from Amass, 1997

<21 days

20 days 21 days 7–10 days

14 days

Salmonella spp.

Mycoplasma hyopneumoniae Pasteurella multocida

Organism

Earliest Recorded Age of Detection

6–14 days (Yes)

4 months (Yes)

<6 weeks

(No)

(Yes)

(May prevent clinical signs)

(Yes)

4 weeks (2 weeks) (Probably)

Duration of Colostral Immunity from Exposed Sows (Is colostral immunity protective against colonization?)

All ages

All ages

All ages, usually piglets and weaners Suckling to finishing, recently weaned All ages

Weaned pigs <5 months old but usually growing/finishing pigs All ages; usually growing/finishing pigs

6 weeks or older, usually 3–6 months old Variable upon disease

Age When Clinical Signs Are Usually Seen

18 hours to 3 days

2–4 days

1–2 days

Hours

2 days to 3 months; usually 10–14 days Days

1–3 days

10–16 days

Incubation Period for Disease

Cats, dogs, foxes, flies

Dogs, cats, raccoons, opposums, rodents, ruminants

Probably not important Rodents, flies

Rodents, flies, birds, mice

Rabbits, dogs, cats, cattle, poultry, turkeys, goats, sheep Many hosts

Other Reservoirs

Abrasions Mange mites Direct contact during birth Transplacental Direct contact Aerosol? Direct contact Insemination Transplacental Aerosol Fomites Ingestion Feces Birds Milk

Fecal-oral

Feces Feed

Direct contact Aerosol Direct contact Aerosol

Mode of Transmission

Multi-site Pig Production

Biosecurity All farms must strive for a biosecure system to minimize the introduction of new infectious agents into the various pig-rearing rooms and/or sites of production. A thorough explanation of the various procedures for maintenance of high biosecurity is given in Chapter 7 (“Biosecurity”). If an infectious agent not found in the herd is introduced either into the farrowing room or to sows late in gestation, the likelihood is high that, at weaning, both MEW and isowean piglets will be infected with the agent, primarily because of low sow immunity or no sow immunity.

Exclusion of Specific Agents by MEW or Isowean Streptococcus suis Type 2 MEW usually excludes Streptococcus suis type 2, but isowean does not. Prior to farrowing, sows were medicated with penicillin. From birth through 10 days of age, the piglets were medicated daily with injectable penicillin or ceftiofur. The piglets were weaned at 5 days of age. (Tom Alexander indicates that this procedure cannot eliminate all types of Streptococcus suis; however, MEW can definitely be used to produce batches of pigs free of virulent S. suis, such as types 1/2, 1, 2, 9, and 14.)

Pasteurella multocida (Toxigenic Strains) Isowean has produced pigs free of the toxigenic form of Pasteurella multocida, which is the main cause of atrophic rhinitis. Four weeks and 2 weeks prior to farrowing, sows were immunized with P. multocida vaccine containing antigen to the toxin. Three to 4 days before farrowing, sows received an intramuscular injection of 500 mg of ceftiofur. Sows were housed in all-in/all-out rooms; all farrowings in each room were within 3–5 days of one another. Piglets were weaned at 7–10 days of age. Each piglet received four intramuscular injections of ceftiofur at these days of age: 1, 5, 7–10, and 12–15 (5 days post-weaning). The amount of ceftiofur injected was 10, 20, 20, and 30 mg respectively.

Mycoplasma hyopneumoniae The Isowean Principle has produced pigs free of Mycoplasma hyopneumoniae. Immunize sows with a M. hyopneumoniae vaccine 4 and 2 weeks prior to farrowing. In addition, sows can be injected with lincomycin for 3 consecutive days prior to farrowing. Inject the piglets with long-acting oxytetracycline or lincomycin at 1, 4, 8, 12, and 16 days of age. Wean the piglets on or prior to 16 days of age, but each weaning group should have very narrow age range (1–2 days preferred). The younger the weaning age, the fewer injections required. At weaning, administer tiamulin via the water for 14 days.

Pseudorabies (Aujeszky’s) Virus (PRV) Pigs free of PRV can be readily obtained from PRV-infected farms by using isowean. Sows should be vaccinated with gene-deleted vaccine prior to breeding. Piglets can be weaned at 24 days of age or less. 68

3. Exclusion and Elimination of Microbes

Collect blood from pigs less than 12 weeks of age and assay the sera for antibody to PRV. The results will be positive if the sows have been exposed to field strains of PRV. Usually, maternal antibody to field PRV is not present in pigs by 16–20 weeks of age. Sentinel pigs free of PRV can be added to each batch of newly weaned pigs. The sentinel pigs can be bled and their sera can be checked for antibodies to PRV. If sentinel pigs remain negative to the presence of serum antibody to PRV, it is an indication that the isowean pigs are free of the virus.

Porcine Reproductive and Respiratory Syndrome (PRRS) Virus Batches of pigs can be procured from PRRS virus–positive farms by using MEW or isowean. Depending on variables that are not totally understood, some batches from both MEW and isowean will be positive for the virus. The following procedures have been successful in procuring pigs free of PRRS virus from PRRS virus–infected farms by either MEW or isowean: 1. Sows can or cannot be immunized with modified live PRRS vaccine. Do not inject piglets with modified live PRRS vaccine. Killed PRRS vaccine can be used with piglets, but it is probably not necessary and can confuse subsequent serologic evaluations. 2. Maintain a closed herd for replacement of breeding stock. For best results, do not bring in replacements for 6 months prior to the initiation of the MEW or isowean programs. If replacement breeding stock is added to the herd, the gilts and boars should be acclimated for at least 90 days prior to breeding (see Chapter 7, “Gilt Development”). Preferably, replacement breeding stock should be negative for PRRS virus. 3. Wean pigs at less than 10 days of age and have an age difference within a weaning group of 1-2 days. 4. Sentinel pigs from a PRRS-negative farm can be added to each weaning group. Blood collected from the sentinel pigs can be assayed to determine if the PRRS virus is present. After 16 weeks of age, MEW and/or isowean pigs should be free of any passively acquired antibody to the PRRS virus.

Actinobacillus pleuropneumoniae (App) Batches of pigs from infected site 1 sows can be procured free of App via isowean. The pigs may be weaned from 5 to 28 days of age. Best results are obtained if the weaning age per group is not over 3–5 days different from the youngest to the oldest. Both sows and piglets should be injected with tiamulin, enrofloxacin,1 or tilmicosin.

Salmonella spp. Batches of pigs can be procured free of Salmonella spp. from infected site 1 sows via isowean. For best results, pigs should be weaned not older than 10 days of age and should 1. The use of enrofloxacin in swine is not allowed in certain countries.

69

Multi-site Pig Production

be injected with enrofloxacin every 3 days until weaned. The weaning ages per group should not be greater than 2 days, and the farrowing rooms must be cleaned and sanitized before farrowing.

Leptospira spp. Batches of pigs can be procured free of Leptospira spp. from infected site 1 sows via isowean. The following protocol is recommended: 1. 2. 3. 4.

Vaccinate sows with Leptospira bacterin 6 weeks and 2 weeks pre-farrowing. Inject sows with penicillin/dihyrostreptomycin2 prior to farrowing. Wean pigs at 10 days of age by isowean, with 1–2 days variation in age per group. Inject pigs with penicillin/dihydrostreptomycin on 1, 5, and 10 days of age.

Exclusion of Infectious Agents by Multi-site Isowean Production Exclusion of Infectious Microbes via the Isowean Principle Multi-site rearing systems rely on the Isowean Principle for the production of weaned pigs free of microbial pathogens residing in the adult population in the breeding, gestation, and farrowing site(s). The Isowean Principle can be applied to all types of rearing systems as well; however, multi-site rearing incorporates the Isowean Principle within the system either when old facilities are redesigned or when new facilities are constructed on “greenfield” sites. One-site and traditional two-site farms can utilize the Isowean Principle by incorporating an isolated nursery and finisher accommodation for all or part of the weaned pigs produced. In fact, prior to the construction of the first three-site system in 1988, all isowean experimental trials involving elimination of PRV, toxigenic Pasteurella multocida, and Mycoplasma hyopneumoniae were conducted by removing a portion of weaned pigs from existing one-site and traditional two-site farms. The successful exclusion of an infectious agent by the Isowean Principle depends on many factors. The weaning and finishing accommodations are the most important aspect of the procedure since not every weaning group is expected to be free of a particular agent or agents. For this reason, continuous flow pens, rooms, buildings, or loci are not recommended. Nursery and finisher buildings that have pig throughput on an all-in/all-out basis by locus have distinct advantages as well over systems designed with all-in/all-out by room or pen within a building. When one weaning group of pigs in multiple-site isowean or NurFin isowean designs becomes infected with a particular infectious agent, the agent need not spread to other groups weaned before or after the infected group. A generic list of steps to take to eliminate infectious agents by various multi-site isowean rearing systems is as follows: 1. Establish procedures for isolation and acclimatization of incoming replacement breeding stock. If the infectious agent has been recently introduced into the breeding herd (stage 1 loci), it may be necessary to wait until a level of immunity as been 2. The use of dihydrostreptomycin in swine is not allowed in certain countries.

70

3. Exclusion and Elimination of Microbes

2.

3. 4. 5. 6. 7. 8.

achieved in the adults. Furthermore, it may be important to add replacement stock (negative to the infectious agent in question) to the herd immediately following a disease outbreak so that the replacements also become immune to the agent. The length of acclimatization is determined by the infectious agent to be eliminated. Ideally in multiple-source isowean systems, each batch of replacements should be exposed to the infectious agents present in all site 1 (breeding, gestation, farrowing) loci. Vaccinate sows pre-farrowing with vaccines designed to prevent diseases caused by the infectious agents to be reduced or eliminated in the isowean pigs. Vaccines are available in some countries for microbes such as toxigenic P. multocida, M. hyopneumoniae, Haemophilus parasuis, Streptococcus suis, Actinobacillus pleuropneumoniae, Actinobacillus suis, swine influenza virus, and pseudorabies virus. The use of live avirulent vaccines for transmissible gastroenteritis virus and PRRS virus are not recommended for elimination of agents by the Isowean Principle. Administer medications to the sows prior to farrowing based on the infectious agents to be eliminated. Establish management procedures for all-in/all-out throughput of each farrowing room. Set the weaning age based on the infectious agents to be eliminated. Administer medications to the piglets prior to and after weaning based on the infectious agents to be eliminated. Establish management procedures for all-in/all-out throughput for each weaning group in the nursery and finisher. Maintain strict biosecurity procedures (see Chapter 7, “Biosecurity”).

Tables 3.4 through 3.8 give vaccination, medication, and throughput action steps for eliminating specific infectious agents from the following multi-site production systems: 1. Three site (single locus) (Table 3.4). Each of the three stages of production is on a separate location. 2. Three site (multi-loci) (Table 3.5). The production flow is all-in/all-out by locus for each batch of weaned piglets. Pigs then flow from nurseries to finishers on an allin/all-out by locus basis. There can be one or more buildings per locus. 3. Two-site isowean (Table 3.6). Stage 1 production is at one locus and stages 2 and 3 are on another isolated locus. The nursery and finisher buildings contain rooms with all-in/all-out throughput. The nursery and finisher buildings are usually on the same location but separated from one another. 4. NurFin isowean (Table 3.7). Each batch of weaned pigs is placed in a NurFin (weanto-finish) building located on an isolated locus; throughput is all-in/all-out. For a few weeks, temporary flooring (comfort boards), special water drinkers, and supplemental heat are provided for the newly weaned pigs. 5. Outdoor isowean (Table 3.8). Stage 1 production is in an extensive pasture system that has weekly farrowings year-round. Nursery and finisher buildings are placed in isolated locations. For each type of multi-site isowean system, assume that the infectious agent to be eliminated has been introduced into all sites of all three stages of production. If the infectious 71

Multi-site Pig Production

Table 3.4 Procedures for Eliminating Infectious Agents in Three-site (Single-locus) Production Stage 1

Stage 3

Weaners

Finishers

Infectious Agent

Breeders/suckling

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae Streptococcus suis PRRS virus

Vacc/Med.** Vacc/Med.

8–10 14–17

Depopulate Depopulate

Depopulate Depopulate

Vacc/Med.

21

Depopulate

Depopulate

Depopulate Depopulate

Depopulate Depopulate

Depopulate Virus exposure Medicate

Depopulate Virus exposure Depopulate or medicate

PRV TGE virus Serpulina hyodysenteriae

Medicate Virus Exposure No vaccine Vaccinate Virus exposure Vacc/Med.

Age*

Stage 2

5# 5–12 21 21 21

Source: Modified from Harris and Alexander, 1999 *Age to isowean in days. **Vaccinate and medicate. # Medicated early wean for best results.

Table 3.5 Procedures for Eliminating Infectious Agents in Three-site (Multi-loci) Production Stage 1

Stage 3

Weaners

Finishers

Infectious Agent

Breeders/suckling

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae Streptococcus suis PRRS virus

Vacc/Med.** Vacc/Med.

8–10 14–17

AIAO*** AIAO

AIAO AIAO

Vacc/Med.

21

AIAO

AIAO

AIAO No vaccine AIAO AIAO AIAO

AIAO No vaccine AIAO AIAO AIAO

PRV TGE virus Serpulina hyodysenteriae

Age*

Stage 2

5# 5–12

Medicate Virus exposure No vaccine Vaccinate Virus exposure Vacc/Med.

21 21 21

Source: Modified from Harris and Alexander, 1999 *Age to isowean in days. **Medicate/vaccinate. ***All-in/all-out. # Medicated early wean for best results.

72

3. Exclusion and Elimination of Microbes

Table 3.6 Procedures for Eliminating Infectious Agents in Two-site Isowean (Single-locus) Production Stage 1

Stages 2 and 3

Infectious Agent

Breeders/suckling

Age*

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae Streptococcus suis PRRS virus

Vacc/Med.**

10

Depopulate

Vacc/Med.

10

Depopulate

Vacc/Med.

21

Depopulate

PRV TGE virus Serpulina hyodysenteriae

Weaners/finishers***

5# 5–12

Medicate Virus exposure No vaccine Vaccinate Virus exposure

21 21

Depopulate Depopulate No vaccine Depopulate Virus exposure

Vacc/Med.

21

Medicate

Source: Modified from Harris and Alexander, 1999. *Age to isowean in days. **Medicate/vaccinate. ***Assumes site 2 always has both nursery and finishers pig inventories constantly.

Table 3.7 Procedures for Eliminating Infectious Agents in NurFin Isowean (Multi-locus) Production Stage 1

Stages 2 and 3

Infectious Agent

Breeders/suckling

Age*

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae Streptococcus suis PRRS virus

Vacc/Med.** Vacc/Med.

8–10 14–17

AIAO*** AIAO

Vacc/Med.

21

AIAO

PRV TGE virus Serpulina hyodysenteriae

5# 5–12

Medicate Virus exposure No Vaccine Vaccinate Virus exposure Vacc/Med.

21 21 21

*Age to isowean in days. **Medicate/Vaccinate. ***All-in/all-out. # Medicated early wean for best results.

73

Weaners/finishers

AIAO No vaccine AIAO AIAO AIAO

Multi-site Pig Production

Table 3.8 Procedures for Eliminating Infectious Agents in Outdoor Isowean (Single-locus) Production Stage 1 Infectious agent

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae Streptococcus suis PRRS virus PRV TGE virus Serpulina hyodysenteriae

Stage 2

Stage 3 Finishers

Breeders/suckling

Age*

Weaners

Vacc/Med.**

8–10

Depopulate***

Depopulate

Vacc/Med.

14–17

Depopulate

Depopulate

Vacc/Med.

21

Depopulate

Depopulate

Med. Virus exposure No vaccine Vaccinate Virus exposure

5# 5–12

Depopulate Depopulate

Depopulate Depopulate

21 21

Depopulate Virus exposure

Vacc/Med.

21

Depopulate Virus Exposure Medicate

Depopulate or medicate

*Age to isowean in days. **Vaccinate and medicate. ***If AIAO by site is not possible. # Medicated early wean for best results.

agent(s) in question has not been introduced into a particular stage of production, the action step indicated can not be required.

Eradication of Infectious Agents from the Entire Herd Modern-day multi-site production systems apply the Isowean Principle to exclude (or minimize the levels of ) infectious agents at weaning to decrease their effect on the performance of the growing pig. In multi-site isowean rearing, the adult population in site 1 loci can or cannot remain infected with the pathogen(s) being excluded via isowean. Before the development of multi-site isowean rearing techniques in the late 1980s, eradication methods focused on eliminating pathogens from the entire herd. These methods are depopulating, cleaning and disinfecting facilities, and repopulating with high–health status pigs (depop/repop); testing, then removing infected animals; increasing herd immunity; and whole-herd medication. The Jorgan Plomgaard Method has recently been developed for eradicating certain pathogens from entire multi-site isowean herds. The method is based on the work of W. Zimmermann in Switzerland on eradicating M. hyopneumoniae from small traditional herds without total herd depopulation.

The Plomgaard Method Plomgaard was able to eradicate PRRS virus, M. hyopneumoniae, and A. pleuropneumoniae from a three-site farm by: 74

3. Exclusion and Elimination of Microbes

1. Not replacing breeding stock for 3 months. 2. Using whole-herd medication directed against M. hyopneumoniae and A. pleuropneumoniae (enrofloxacin). 3. Removing all breeding animals less than 10 months of age and animals with no serologic titers to PRRS virus and A. pleuropneumoniae. 4. Replacing with stock free of PRRS virus, M. hyopneumoniae, and A. pleuropneumoniae. These steps eliminated those three agents from site 1. The nursery and finisher buildings at sites 2 and 3 were depopulated before receiving isowean pigs free of the agents. It is likely that PRV and TGE virus could be eradicated by the Plomgaard Method, but this has not yet been reported. For one-site and traditional two-site farms, elimination of most infectious agents is by depopulation and repopulation with high–health status stock. Multi-site isowean production decreases the need for total herd depopulation and repopulation via the Plomgaard Method. The efficacy for eradicating specific infectious agents from entire herds is presented in Table 3.9. Depop/repop is the surest way to eradicate infectious agents, assuming that a supply of negative animals is available and the location of the herd is such that reintroduction of the agent is unlikely. However, depop/repop is far more expensive than the other methods because of the interruption in income when no pigs are being produced or sold. Although test and remove, increased herd immunity, whole-herd medication, and the Plomgaard Method are only applicable to specific infectious agents (Table 3.9), they

Table 3.9 Efficacy of Eradication Methods for Eliminating or Removing Pathogens from Existing Pig Farm Operations Agent

Depop/ Repop

Test/ Remove

Pasteurella multocida Mycoplasma hyopneumoniae Actinobacillus pleuropneumoniae PRV (Aujeszky’s virus) TGE virus PRRS virus Serpulina hyodysenteriae Salmonella spp. Streptococcus suis type 2 Haemophilus parasuis Bordetella bronchiseptica Parvovirus Influenza virus Leptospira spp.

Increased Immunity

Medication*

Plomgaard Method**

? ? ?

?

Eradication very likely Eradication not likely *Whole-herd medication in combination with rodent control and sanitation programs. **Plomgaard, 1998, as developed for multi-site isowean herds only.

75

Multi-site Pig Production

Table 3.10 Financial Impact of Swine Dysentery (SD)

Profit margin/100 kg

SD-free

Endemic SD*

Medication Eradication**

Depop/repop

$7.44

$1.67

$4.93

$0.07

Source: Modified from Polson, Marsh, and Harris, 1992. *Controlled by medication. **Without depopulation.

are not as costly as depop/repop. For example, eradication of Serpulina hyodysenteriae, the cause of swine dysentery, by whole-herd medication is far less costly than depop/repop or “living with” the disease (Table 3.10).

Summary There are more helpful microbes, by far, than harmful ones. The harmful microbes are often referred to as infectious agents or pathogens because they can cause disease. Disease occurs when something detrimental happens to the pig. Some diseases are caused by pathogens. When disease-causing microbes are excluded from the growing pig (by being prevented from infecting the pre-weaned pig), pigs perform better, have leaner carcasses, and are more profitable. Multi-site isowean pig production reduces or excludes pathogens from the growing and finishing stages of production. By using the Plomgaard Method, pathogens can be eradicated from entire multi-site isowean production systems. The newborn piglet is exposed to microbes during and immediately following birth. Piglets rarely are infected with pathogens in utero. In general, MEW and isowean are practical methods for the exclusion of most pathogens. The main factors influencing the successfulness of infectious agent exclusion by MEW or isowean are the levels of sow and piglet immunity, weaning age and the age variation within each weaning group, medications administered to sows and piglets, sanitation, all-in/all-out throughput, and biosecurity measures. These factors, plus the ability of the older breeding-age animal to eliminate an infectious agents, are important in the Plomgaard Method. Medicated early weaning and isowean are used to exclude pathogens from most batches of pigs. These batches of high–health status pigs are used to stock new or depopulated herds. The various types of multi-site systems as described in Chapter 2 use the Isowean Principle to reduce or eliminate various pathogens for the grower and finisher phases of production within ongoing swine herds.

Bibliography Alexander, T. J. L. 1998. Personal communication. Alexander, T. J. L., K. Thornton, G. Boon, R. J. Lysons, and A. F. Gush. 1980. Medicated early weaning to obtain pigs free from pathogens endemic in the herd of origin. Veterinary Record 106:114–119.

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Amass, S. 1997. The effect of wean age on pathogen removal. Nuts and Bolts of SEW Multi-site Systems, 20–32. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Amass, S. 1998. The effect of weaning age on pathogen removal. Compendium on Continuing Education for the Practicing Veterinarian 20:5196–5203. Bruna, G., S. Cabeza de Vaca, H. Joo, and C. Pijoan. 1997. Comparison of techniques for controlling the spread of PRRS in a large swine herd. Swine Health and Production 5:59–65. Clark, L. K., M. A. Hill, T. S. Kniffen, W. VanAlstine, G. Stevenson, K. B. Meyer, C. C. Wu, A. B. Scheidt, K. Knox, and S. Albregts. 1994. An evaluation of the components of medicated early weaning. Swine Health and Production 2(3):5–11. Clifton-Hadley, F. A., T. J. L. Alexander, and M. R. Enright. 1986. The epidemiology, diagnosis, treatment and control of Streptococcus suis type 2 infection. Proceedings of the American Association of Swine Practitioners (March):473–491. Connor, J. 1990. Modified medicated early weaning. Proceedings of the American Association of Swine Practitioners 261–265. Connor, J., R. Baker, B. Christianson, and D. L. Harris. 1994. Leptospira interrogans serovar Pomona elimination through isowean. Proceedings of the 13th International Pig Veterinary Society Congress, Bangkok, Thailand, 231. Dahl, J., A. Wingstrand, D. L. Baggesen, and B. Nielsen. 1996. Eradication of Salmonella typhimurium by strategic removal of pigs in infected herds. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 173. Dee, S. A., and T. W. Molitor. 1998. Elimination of porcine reproductive and respiratory syndrome (PRRS) virus using a test and removal process. Allen D. Leman Swine Conference. Vol. 25. 1998, 187–189. Veterinary Outreach Programs, University of Minnesota, St. Paul. Donadeu, M., M. Arias, C. G.-T. M. Aguero, L. J. Romero, W. T. Christianson, and J. M. SanchezVizcaíno. 1999. Use of PCR to monitor PRRS status of piglets derived by hysterectomy and fostering, isowean, and medicated early weaning. Swine Health and Production (submitted for publication). Fedorka-Cray, P. J., D. L. Harris, and S. C. Whipp. 1997. Using isolated weaning to raise salmonella-free swine. Veterinary Medicine 375–382. Fenwick, B., D. L. Harris, M. Rider, and M. Chengappa. 1996. Serologic validation of the utility of early weaning in preventing sow-to-piglet transmission of Actinobacillus pleuorpneumoniae: Production of disease-free pigs from infected breeding herds. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 482. Geiger, J. O., D. L. Harris, P. J. Armbrecht, B. S. Wiseman, H. T. Hill, K. B. Platt, J. D. Pillen, J. L. Anderson, B. C. Kruse, L. A. Anderson, and H. Baker. 1991. Elimination of pseudorabies virus from three herds utilizing isolated weaning. First International Symposium on the Eradication of Pseudorabies, St. Paul, Minnesota, 67. Geiger, J. O., D. L. Harris, S. L. Edgerton, W. Jackson, J. M. Kinyon, R. D. Glock, J. F. Connor, and D. E. Houx. 1992. Elimination of toxigenic Pasteurella multocida utilizing isowean threesite production. Proceedings of the American Association of Swine Practitioners 45–47. Harris, D. L. 1987. Eradication of transmissible gastroenteritis virus without depopulation. Proceedings of the American Association of Swine Practitioners 555–561. Harris, D. L. 1988. Alternative approaches to eliminating endemic diseases and improving performance of pigs. Veterinary Record 123:422–423. Harris, D. L. 1990a. The use of isowean three-site production to upgrade health status. Proceedings of the 11th International Pig Veterinary Society Congress, Lausanne, Switzerland, 374.

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Harris, D. L. 1990b. Isolated weaning—Eliminating endemic disease and improving performance. Large Animal Veterinarian 10–12. Harris, D. L. 1990c. The use of isoweantm three-site production to upgrade health status. Proceedings of the 11th International Pig Veterinary Society Congress, Lausanne, Switzerland, 374. Harris, D. L. and T. J. L. Alexander. 1999. Methods of disease control. In Diseases of Swine, 8th ed., ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor. Iowa State University Press, Ames, Iowa. Harris, D. L., P. J. Armbrecht, B. S. Wiseman, K. B. Platt, H. T. Hill, and L. A. Anderson. 1992. Producing pseudorabies-free swine breeding stock from an infected herd. Veterinary Medicine (February):166–170. Haye, S. M. and E. T. Kornegay. 1979. Immunoglobulin G, A, and M and antibody response in sow-reared and artificially-reared pigs. Journal of Animal Science 48:1116–1122. Plomgaard, J. 1998. Eradication of PRRS from the swine herd. Allen D. Leman Swine Conference. Vol. 25. 1998, 194. Veterinary Outreach Programs, University of Minnesota, St. Paul. Patience, John. 1997. Segregated early weaning. Nuts and Bolts of SEW Multi-site Systems. Preconference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Polson, D. D., W. E. Marsh, and D. L. Harris. 1992. Financial considerations for individual herd eradication of swine dysentery. Proceedings of the 12th International Pig Veterinary Society Congress 510. Ross, D. R., and R. S. Cutler. 1992. “Snatch farrowing”: A new way of introducing genes to a pig farm. Proceedings of the Australian Association of Pig Veterinarians 118–120. Thompson, R. and R. Tubbs. 1998. Personal communication. Underdahl, N. R. 1973. Specific Pathogen-free Swine. University of Nebraska Press, Lincoln. Wiseman, B. S. 1997. Disease Elimination, Immunological and Growth Performance in Modified Medicated Early Weaned Pigs, Ph.D. dissertation, 1–176. University of Minnesota, St. Paul. Zimmermann, W. 1990. Experiences in the EP sanitation programme to eradicate EP. Tierarztl Umschau 45:556-562.

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A high level of immunity to a pathogen in the dam often is related to the successful elimination of the infectious agent in both the adults and the suckling pig via the Isowean Principle. Overstimulation of the immune system of growing pigs due to chronic infection and poor sanitation results in poor performance and meat quality. If managed properly, multi-site isowean pig production minimizes disease and maximizes growth rates and lean tissue deposition in growing pigs. But as the level of a pathogen is decreased in a multi-site isowean system, the level of immunity (or resistance) in the breeding herd to the disease associated with that pathogen may also decrease. Vaccines can be used to maintain a high level of immunity in the dam but highly efficacious vaccines do not exist for all possible pathogens. Many factors contribute to the overall level of immunity in the herd (herd immunity), including the pig itself (genetics), weaning age (and if and when the young pig is separated from the adult population), parity distribution, replacement rate of breeding stock, facility design, sanitation, and the nature of and degree of exposure to the infectious agent. The interaction between these factors is what determines the level of immunity in a herd, as well as whether new diseases emerge or old ones re-emerge. Understanding both this “Catch 22” between immunity and the levels of infectious agents, and the complex interactions of the pig, its environment, and microbes is critical to producing pigs via the Isowean Principle. Originally, modern-day multi-site rearing systems were developed to eliminate infectious agents from piglets, via the Isowean Principle, specifically for the production of breeding stock. But it was soon discovered that piglets grew much faster when reared by the Isowean Principle than when reared in the environment of other age groups on the farm. Thus, just as all-in/all-out production improves the performance of pigs, when allin/all-out concepts are combined with the Isowean Principle, pigs perform even better! When managed properly, multi-site pigs reared via the Isowean Principle result in as much as $12 greater profitability per pig than pigs produced in one-site and traditional two-site systems. Furthermore, the increased profitability can be achieved without total elimination of infectious agents. In many instances, the pathogen merely needs to be reduced in the growing pig to maximize profitability and pig performance.

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Isowean pigs can be more profitable. This is because isowean pigs have more efficient feed conversion, and improved growth rates and lean-gain. Isowean pigs are exposed to fewer microbial antigens that are associated with chronic disease and poor sanitation. This decrease in antigen exposure is due to: 1. Elimination and/or reduction of exposure to disease-causing microbes. 2. Reduced exposure to non-disease-causing microbes normally present in the pigrearing environment. 3. Reduced exposure to the endotoxins derived from decomposing microbial cell walls and other microbial toxins present in the pig-rearing environment.

Antigens, Antibodies, and Immunity Microbes and microbial toxins that can cause harm or endanger the pig are recognized as being foreign by the pig’s immune system. The immune system produces antibodies in response to the microbes and their toxins. The more antigens the pig encounters, the more antibodies it produces. Antigens and antibodies react in a lock and key arrangement when they encounter one another (Figure 4.1). When antibody interlocks with an antigen, it usually helps the pig eliminate the antigen from the body. The elimination of antigens associated with an infectious agent usually results in a reduction of the severity of any disease associated with the pathogen. Immunity is a term indicating that antibodies in the pig’s body are playing a role in counteracting the detrimental effects of microbial antigens. There are three main types of antibodies: IgG, IgM, and IgA. IgM is a large antibody that is produced quickly by the body in response to an antigen. IgM can interlock with more than two antigens, so it is very efficient. IgG and IgA are produced later than IgM. IgG and IgM function mainly in the blood and in large body organs like the liver and spleen. IgA functions mainly in the intestinal and respiratory tracts and in areas of the body with secreting surfaces such as the eyes, joints, and reproductive organs. IgG and IgA can bind only two antigens at once, but they are produced in larger amounts than is IgM. The sow provides the piglet with passive immunity until it can develop its own active immunity. The piglet acquires IgG, IgM, and IgA antibodies (passive immunity) from the dam. IgG from the colostrum is absorbed into the blood by the piglet. IgA and IgM present in the colostrum and milk protect the piglet against intestinal disease during their passage through the gut (Figure 4.2A, B; Table 4.1). These colostral antibodies protect the pig against disease from a wide range of infectious agents until it can produce its own antibodies and have active immunity. However, these antibodies do not last very long. By the time the piglet is 3 weeks old, over one-half of the antibodies received via the colostrum have disappeared. Fortunately, as the pig grows older, it produces its own IgG, IgM, and IgA antibodies, which is referred to as active acquired antibody production (Figure 4.2A,C). This comes

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Figure 4.1 The lock and key configuration of antibody/antigen interactions.

about because as the pig ages, it is exposed to more and more antigens in its environment. In one-site and traditional two-site systems, the levels of exposure to antigens are much greater than in multi-site systems utilizing the Isowean Principle. Poor sanitation in any production system increases the amount of antigen exposure to the growing pig. Antibodies are proteins composed of amino acids. Antibodies require some of the same amino acids for their creation as the proteins in muscle tissue do. Thus, there is a competition between antibody production and protein deposition for muscle development. Amazingly, if amino acids are diverted into antibody production, the body also tends to increase its production of fat. To maximize protein deposition into muscle, piglets should be reared with as little exposure to infectious agents and harmful antigens as possible to reduce antibody production (Table 4.2). The overproduction of antibodies can literally rob the body of amino acids necessary for growth and protein deposition in muscle!

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Figure 4.2 Antibodies in colostrum and milk (passive immunity) protect the piglet prior to the production of its own antibodies (active immunity). (Modified from Porter and Allen, 1972)

Table 4.1 Characteristics of Colostral and Milk Antibodies for Passive Immunity Before the Piglet Initiates Active Immunity • Antibody colostral concentrations increase with increased parity • Antibody concentrations decline in colostrum about 3.4%/hour for the first 24 hours after parturition • Colostrum contains IgG, IgA, IgM antibodies, while milk contains primarily IgA antibodies • Antibody concentration varies among adjacent mammary glands, with the highest concentration in caudal glands • Intestinal absorption of IgG antibody occurs for the first 24–36 hours after birth • Absorption time may be increased for pigs that were starved during this period of time • Intestinal absorption of IgA and IgM is not efficient, but it provides intestinal protection • After first exposure to pathogen, approximately 7–10 days are needed for the piglet to initiate an active immune response (Figures 4.2 and 4.9) Source: Modified from Amass, 1997.

Exposure of MEW and Isowean Pigs to Antigens Pigs reared via the Isowean Principle are exposed to fewer infectious agents and harmful microbial antigens. As a result, the pig’s immune system is not as highly stimulated by the various components (antigens) of these pathogenic microorganisms. In addition, due to separation of age groups and all-in/all-out management procedures in multi-site systems, pigs are usually reared under very sanitary conditions. This results in less stimulation of 82

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Table 4.2 Effects of Different Rearing Systems on Antigenic Exposure, Fat Deposition, Protein Accretion, and Rate of Growth of the Pig Multi-site AIAO High–Health Status Sanitary

➞➞

➞➞

➞➞

➞➞

Antigenic Exposure Fat Deposition Protein Accretion Rate of Growth

One Site Continuous Pig Flow Chronic Disease Unsanitary

Figure 4.3 Levels of endotoxin in the air of nursery rooms of isowean pigs reared in an isolated nursery and of littermate control pigs reared in a nursery on a one-site farm.

the pig’s immune system by antigens associated with the non-disease microorganisms normally present in the feces. The environment of the isowean nurseries contains less endotoxin (cell wall lipopolysaccharides of bacteria normally found in feces) in the air than in nursery rooms on one-site farms (Figure 4.3).

Pig Performance with Less Antigen Exposure via the Isowean Principle Less antigen exposure improves pig performance. Pigs reared via the Isowean Principle gain weight more rapidly and efficiently (see Figure 2.3). The profoundly improved performance is due to less antigenic exposure of the pig’s immune system to non-pathogenic microbes normally found in the feces, microbial components (such as endotoxin), and pathogenic agents associated with various infectious diseases. When the pig’s immune 83

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Table 4.3 Body Growth of Isowean Pigs and Control Pigs Reared in a Nursery on a One-site Farm Item

Isowean

Control

Change

.231 .149 .64

.144 .138 .95

+.087 +.111 –.31

Composition of body growth Protein gain (lb/d) Fat gain (lb/d) Fat to protein gain Source: Modified from Stahly, 1996.

Figure 4.4 Thymus glands of an isowean pig reared in an isolated nursery (bottom) and of a control pig reared in a nursery on a one-site farm (top).

system is exposed to high levels of antigens, energy and amino acids needed to produce antibodies are diverted away from muscle protein accretion (Table 4.3). Pigs reared by isowean have larger thymus glands and produce less antibodies than pigs reared in one-site farms (Figures 4.4 and 4.5). In addition, when the pig’s immune system is overly stimulated by disease-causing microorganisms and other antigens, hormonelike compounds called cytokines are released into the body. These cytokines decrease food 84

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Figure 4.5 Mean thymus gland weights of isowean pigs reared in an isolated nursery and of control pigs reared in a nursery on a one-site farm. (Data from approximately 20 pigs per experiment.)

intake, decrease the body growth rate and the efficiency of food utilization, and decrease protein synthesis associated with lean-tissue deposition. Antigenic stimulation of the immune system involves a very complex series of steps and cellular interactions within the body. Isowean pigs appear to have large thymus glands because the monocytic (lymphocyte) cells present in the gland are not “called out” to respond to antigens. Monocytic cells in the thymus are named T lymphocytes and can be categorized by components on their surfaces referred to as clusters of determination (CD). The CD 4 lymphocytes are called T helper cells and are active in defense against bacterial infections. The CD 8 lymphocytes, which are called cytotoxic T cells, help destroy pig cells infected with viruses. When the CD 4 and CD 8 T lymphocytes begin proliferating (outside the thymus gland) and participate in defending the body by activating antibody production, cytokines are produced. The cytokines are necessary for antibody production but, unfortunately, they also have a profound negative effect on metabolism. Three important cytokines are interleukins 1 and 6 (IL-1, IL-6) and tissue necrosis factor (TNF). For example, IL-1 and TNF both can decrease voluntary food intake, while IL-1 and IL-6 can increase corticosterone release. Cytokines released from monocytes after antigenic stimulation cause increased adrenocorticotropic hormone (ACTH) production in the pituitary and corticosterone in the adrenal gland. This decreases thymosin output and continues the depletion of monocytic cells from the thymus, which results in decreased growth hormone production by the pituitary.

Piglet Nutritional Requirements and the Lean/Gain Ratio Nutritional requirements for pigs have been established under various housing and management conditions. Some of the variation in previous studies used to determine these 85

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requirements can now be explained because the level of antigen exposure was not controlled, which confounded the results. The Isowean Principle has altered the nutritional requirements of piglets. Pigs reared via isowean have a higher requirement for lysine (Tables 4.4 and 4.5). The additional lysine is needed due to the increase in lean tissue accretion. Requirements for other nutrients by pigs reared in this manner may also need to be adjusted. The increased lysine requirement results in an increase in protein accretion in muscle tissue and a decrease in fat deposition. Therefore, pigs gain weight more rapidly and efficiently and have improved lean tissue/gain ratios compared to pigs reared in one-site farms. In addition, less nitrogen (N) is excreted from the pig reared in via isowean due to increased amino acid (lysine) consumption and increased N retention in the form of protein. The health status of pigs also is related to the type of ration (food) the pig consumes. Profits could be profoundly effected if a costly ration is fed to pigs of low health status.

Table 4.4 Average Daily Gain and the Body Weight Gain per kg of Feed as Influenced by Percent Lysine in the Ration for Isowean Pigs and Control Pigs Reared in a Nursery on a One-site Farm Dietary lysine (%)

.60

.90

1.20

1.50

1.80

ADG (g)

Isowean Control

475 359

577 478

652 531

677* 475

624 494

GF (g/kg) Isowean Control

425 417

550 515

658 585

696 551

632 564

Source: Modified from Williams, Stahly, and Zimmerman, 1997. Note: Pig weight increased from 6 kg to 27 kg during the nursery stage. *Bold type indicates the highest number in each group.

Table 4.5 Average Daily Gain, Body Weight Gain per kg of Feed, and Percent Carcass Muscle as Influenced by Percent Lysine in the Ration for Isowean Pigs and Control Pigs Reared in a Finisher on a One-site Farm Dietary lysine (%)

.45

.60

.75

.90

1.05

ADG (g)

Isowean Control

657 510

884 792

923 792

896 778

967* 703

GF (g/kg)

Isowean Control

259 281

328 315

372 318

363 329

347 298

Muscle (%) Isowean Control

48.5 48.8

51.7 50.7

54.9 52.3

57.0 52.5

Source: Modified from Williams, Stahly, and Zimmerman, 1994. Note: Pig weight increased from 27 kg to 114 kg during the finisher stage. *Bold type indicates the highest number for each group.

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Interactions of the Nervous and Immune Systems The nervous and immune systems of the pig interact in complex ways. Physical, visual, and emotional stress can activate the same cytokines that are induced by exposure to the antigens of infectious agents and other microbes. Thus, environmental stress, overcrowding and chilling in particular, can affect the growth, protein accretion, and fat deposition of pigs. The nervous and immune systems may interact to depress growth hormone production. The immune system is affected by chronic infection and poor sanitation, which results in high antigenic stimulation. The nervous system may be stimulated by physical, emotional, and visual stressors. Stimulation of either or both systems can activate monocytes (lymphocytes), which trigger cytokine releases that eventually depress growth hormone output and growth. Isowean minimizes antigenic stimulation of the immune system and thus, in the absence of neurologic stressors, enhances protein accretion and growth. Large thymus glands indicate high health status, little or no depletion of T lymphocytes due to minimal antigenic stimulation, and maximal growth hormone output. Figure 4.6 illustrates the effect of stress, chronic infection, and poor sanitation on pig growth. Figure 4.7 illustrates the enhanced growth hormone effect present in isowean pigs.

Figure 4.6 The effect of stress, chronic infection, and poor sanitation on pig growth.

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Figure 4.7 The enhanced growth hormone effect present in isowean pigs.

Management and Biosecurity Measures Excellent management and biosecurity measures are critical for rearing pigs via the Isowean Principle. If isowean pigs are reared in conditions of poor hygiene or improper biosecurity or in stressful conditions, the advantages in pig performance are readily compromised (Table 4.2). In such situations, diets may need to be adjusted accordingly to reduce the cost of production.

Performances of Isowean Pigs and Pigs Weaned from Traditional Two-site Farms Repeated experimentation has shown that isowean pigs outperform littermate pigs that are reared in one-site or traditional two-site farms. In most of these studies, some level of infectious agents were present, even though the farms may have been considered of relatively high health status. 88

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Table 4.6 Performance in the Finisher Stage of Single-source and Multiple-source Pigs on Multi-site Farms in Chile, January–August 1998. (Data kindly supplied by Gonzalo Castro, Super Pollo.)

No. pigs in Weight in (kg) Age In (days) No. pigs out Age out (days) Weight out (kg) ADG, from birth (g) ADG, grower (g) ADFI (kg) F/C First Class (%) Mortality (%)

Traditional Two Site (Multi-source)a

Three Site (Multi-source, Multi-loci)b

Three Site (Single source, Multi-loci)c

310,730 28.46 74.53 298,714 174.46 112.08 641 836 244.36 2.94 98.70 0.957

374,275 27.58 69.83 370,740 171.72 111.92 652 829 246.84 2.93 98.74 0.945

59,027 26.64 69.30 58,555 170.65 110.38 647 826 238.69 2.85 98.80 0.824

Source: Gonzalo Castro, Super Pollo, October 1998 aPigs were mixed from multiple sources at 74.53 days of age. bIsowean pigs originated from multiple sources and then reared in an all-in/all-out nursery at site 2 and all-in/all-out finisher at site 3. cIsowean pigs originated from a single source and then reared in an all-in/all-out nursery at site 2 and an all-in/all-out finisher at site 3.

Gonzalo Castro has compared the performance in the finisher production stage of pigs reared on traditional two-site (multi-source), three-site (multi-source, multi-loci), and three-site (single source, multi-loci) farms (Table 4.6). These pigs were born and reared in Chile from herds known to be free from the infectious agents of porcine reproductive and respiratory syndrome (PRRS) virus, coronaviruses, and transmissible gastroenteritis (TGE) virus. The herds were infected with Mycoplasma hyopneumoniae. The results indicate there is no advantage of rearing isowean pigs over traditionally grown pigs when isowean pigs are from multiple sources. Steve Drum reported similar results in a study in the United States with fewer numbers of pigs per group. It is possible that differences between isowean and traditionally reared pigs will not vary considerably if the pigs are derived from very high–health status herds.

Piglet and Sow Immunities If the dam has been exposed to an infectious agent (antigens), she will produce antibodies to the infectious agent in her colostrum and milk (Table 4.1). Thus, a piglet nursing such a dam will often be protected against disease. This contributes to the weaning of isowean pigs free of certain pathogens. When the isowean piglet is weaned into a clean and biosecure environment, its immune system is more robust and able to resist infections because large thymus glands respond better to antigens and thus produce antibodies. 89

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In any group (defined as pigs weaned at the same time by the same method of rearing) of isowean pigs, littermates from one non-immune sow could become infected prior to weaning. Because of passive immunity, this occurrence of a few infected pigs does not usually result in a serious deterioration of performance of the group as whole. Although the nature of the infectious agent is important in such situations, the immune system of the isowean pig is primed to handle such relatively mild onslaughts of pathogen exposure.

Herd Immunity A newly introduced pathogen will often spread rather rapidly through all pigs in a herd. The more virulent or pathogenic the infectious agent, the more severe the disease. If the pathogen does not cause death of the entire herd, pigs that recover from the disease will likely become immune to reinfection and resistant to reoccurrence of disease symptoms. As more and more pigs become resistant in this manner, the level of herd immunity increases. The reasons for this increase in herd immunity are quite complex. The main contributing factors are decrease in the virulence of the infectious agent, age resistance, genetic resistance, and passive immunity. In some instances, the phenomenon may account for the disappearance of an infectious agent from a herd. Herd immunity is more apt to develop in a closed herd that does not bring in susceptible mature replacement breeding stock. The concept of herd immunity is utilized frequently for the elimination of transmissible gastroenteritis virus from entire one-site and multi-site herds without depopulation (see Chapter 5, “Transmissible Gastroenteritis”). Herd immunity also plays an important role in eliminating pathogens from multi-site isowean herds by the Plomgaard Method (see Chapter 3, “Eradication of Infectious Agents from the Entire Herd”). In this case, the separation of the weaned growing pigs by the Isowean Principle seems to hasten the disappearance of certain pathogens (PRRS virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae) from the site 1 adult population. Thus, the development of herd immunity is favored in one-site and traditional two-site farms due to the greater chance of continual exposure (the common air-space shared by pigs in the various stages of production) of all population age groups to pathogens present in the herd. Therefore, herd immunity may wane or not develop as expected in a multi-site isowean production system. If this occurs, subpopulations of adults with varying degrees of immunity (zero to high) may develop. In such cases, elimination of an infectious agent by the Isowean Principle that is dependent upon the immune status of the sow may be compromised. By contrast, if the older adult population does get exposed to a pathogen and develop an immune response, multi-site isowean systems can favor the elimination of the agent from the adult population under certain management procedures. In the Plomgaard Method of eradicating pathogens from the entire herd, replacement stock to the breeding herd must be negative for the pathogen(s) of concern. If replacement animals are infected with the pathogen or if a large number of uninfected replacement gilts are being added frequently to the herd, eradication of the pathogen will be unlikely. 90

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Immune Status of the Dam In one-site and traditional two-site farms, there is a greater chance for exposure of all age groups to the various microbes resident within the facility. The separation of age groups in multi-site isowean rearing can result in a decrease in antigen exposure of the dam. This fact is contradictory to the general objective of maximizing the immune protection to the isowean piglet via passively acquired antibodies in the colostrum and milk. One can theorize that the isowean pigs procured in batches from either one-site or traditional two-site farms may have a greater frequency of microbial elimination due to the better immune status of sows (high herd immunity) in such systems. By contrast, sows in multi-site farms, by the very design of the system using the Isowean Principle, may have a lower immune status (low herd immunity) due to minimizing antigenic exposure. In multi-site isowean farms, the sows may not be exposed to as high levels of antigens as on one-site farms because of the separation of the stages of production. Whether this is, in fact, true has never been tested experimentally. It is less likely to be a factor when efficacious vaccines for the particular infectious agent to be eliminated are used prior to farrowing to immunize the sow. (See Chapter 3, “Elimination of Infectious Agents by MEW and Isowean,” for exceptions or difficulties associated with this, depending upon the pathogen in question.)

Emerging Infectious Diseases In one-site and traditional two-site farms, particularly in those using replacement females reared on the same farm, the level of herd immunity to the pathogens endemic in the breeding herd is maximized. This is because infectious agents are maintained most commonly in the young growing pigs. In multi-site isowean production, there is distinct separation of wean-to-finish pigs from the endemic pathogens in the breeding herd. Therefore, pigs reared via the Isowean Principle and introduced into the breeding herd can be extremely naive to many microorganisms present in stage 1 of production. Furthermore, the lack of a steady supply of pathogens being carried into stage 1 by replacement animals may decrease the level of maternal immunity provided to the pigs weaned by the Isowean Principle. As time passes, new pathogens emerge and known pathogens of the past re-emerge in swine populations (as with infectious diseases in all animals and humans). Before the development of multi-site isowean systems of production in the late 1980s, the weaning age of piglets had been gradually decreasing in modern pig production. For example, piglets were routinely weaned at 6–8 weeks of age in the midwestern United States in the 1950s. Whereas since 1980, weaning age has decreased to around 17–21 days of age. Decreasing the weaning age of pigs and all-in/all-out management procedures may have resulted in the emergence of Streptococcus suis type 2 infections, Glasser’s disease caused by Haemophilus parasuis in the 1980s. With a weaning age of 21 days, producers were able to stop continuous flow nursery management and to more readily improve 91

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sanitation. This may have decreased the level of infectious-agent exposure of suckling pigs. An early-weaned pig (less than 3 weeks of age) may not be infected with a pathogen until after weaning. Whereas a pig weaned at 8 weeks of age is more likely to be exposed to pathogens prior to weaning and before the loss of antibodies passively acquired from the dam in the colostrum (Figure 4.2). If piglets are exposed to pathogens around 1–3 weeks of age while high levels of passively acquired antibodies are present, it may allow time for active acquired antibody production by the pig to resist disease occurrence. If the pig is exposed to a pathogen for the first time after the loss of passively acquired antibodies from natural decay (50% of IgG is lost every 21 days), then the piglet may not have time to develop an acquired active immunity and disease will occur (Figure 4.8). Multisite isowean production systems may exacerbate this situation by decreasing the level of herd immunity and thus decreasing the level of maternal colostral and milk protection available to the piglet during lactation. These facts may help explain certain experimental results, around 1985 to 1990, of studies of isowean technology. Many scientists and veterinary practitioners determined that a variety of infectious agents could be eliminated by isowean if the pigs were procured from one-site or traditional two-site farms. The pigs in these farms had a high level of herd immunity to a variety of pathogens. Subsequently, many multi-site farms were built around the world that mixed isowean pigs at weaning from multiple sources. Sometimes increased levels of disease occurred in the weaned pigs, probably due in part to the waning of herd immunity and the variation in herd immunity by locus in the site 1 adult population in three-site (multi-source, multi-loci) herds.

Figure 4.8 Influence of age of exposure of pigs to infectious agents on immunity and disease level.

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Carlos Pijoan, Lucina Galina, and Montserrat Torremorell at the University of Minnesota have extensively studied the respiratory tract colonization patterns of the bacterial flora of the pig. They list five risk factors for the development of disease from Streptococcus suis type 2 and Haemophilus parasuis: • • • • •

Early weaning Isowean Degree of virulence of the infectious agents in the pig population Proportion of sows of lower parity (high numbers of gilt introductions) Immunosuppressive infectious agents (such as PRRS virus) present in the population

The development of multi-site systems may be contributing to the emergence and reemergence of pathogens. Depending upon the infectious agent to be eliminated, the weaning ages for isowean pigs vary considerably but are nearly always less than 21 days of age. The evolution toward multi-site isowean systems has further supported the concept of all-in/all-out production coupled with improved sanitation methods. The combination of weaning at less than 21 days, all-in/all-out throughput, and improved hygiene certainly decreases the likelihood of microbial exposure of the piglet prior to weaning. Therefore, multi-site isowean systems require high standards of biosecurity to minimize the introduction of infectious agents into the facilities of growing pigs postweaning. There appears to be an emergence of some infectious agents in multi-site isowean systems that have not been significant problems in one-site or traditional two-site farms. Emerging pathogens include Actinobacillus suis, H. parasuis, circovirus, and S. suis type 2. Emerging pathogens like H. parasuis were not significant pathogens in one-site and traditional two-site herds except when first introduced into a herd. After the initial outbreak of Glasser’s disease, adequate herd immunity would develop in most herds and the piglets would be exposed prior to weaning. It has been suggested by Pat Halbur and Eileen Thacker that herds infected with either or both porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae may be immunologically suppressed and thus more susceptible to these emerging pathogens. The immune status of the breeding-age animals (and thus herd immunity) can be increased by the use of vaccines and a proper acclimatization program for replacement breeding stock. In the United States, it is rather common for sows to be vaccinated for the following disease agents: M. hyopneumoniae, H. parasuis, Leptospira spp., Erysipelothrix rhusiopathiae, and swine influenza virus. Porcine reproductive and respiratory syndrome (PRRS) avirulent live virus vaccine is frequently used as well. In order to decrease the reproductive problems due to PRRS, many farms now acclimatize gilts for 60–90 days prior to introducing them into the breeding herd. Often, these animals are exposed to cull sows and boars that have been placed in the acclimatization facilities (Figure 4.9). When the replacement gilts are from PRRS-negative source farms, this acclimatization procedure has been quite successful for decreasing respiratory disease due to PRRS virus, particularly in multi-site production systems. A long-term acclimatization period also enhances immunity of the gilt to other pathogens and thus 93

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Figure 4.9 Acclimatization for PRRS virus.

increases herd immunity and decreases the negative effect of low parity (see Chapter 5, “Porcine Reproductive and Respiratory Syndrome”).

Summary The complex interactions of factors associated with immunity and pig performance relate to both resistance to disease and to the emergence of disease. Piglets produced by the Isowean Principle are far more susceptible to disease than traditionally reared pigs; thus 94

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management requirements and biosecurity measures must not be compromised in multisite production systems. Rearing pigs in multi-site production systems via the Isowean Principle can result in greater profits than with one-site production. Isowean pigs require additional lysine to maximize lean tissue deposition, which increases production costs. However, when properly managed, pigs produced by multi-site are more profitable due to the realization of their genetic potential in lean gain and feed efficiency. If the health status of multi-site isowean pigs is decreased by infectious-agent introduction during the growing period, the economic advantage may be lessened considerably unless dietary adjustments are made. The Isowean Principle, and thus multi-site pig production, may be contributing to the emergence of infectious disease agents, especially in poorly managed operations. This possibility combined with immune suppression induced by PRRS virus and M. hyopneumoniae infections may contribute to the emergence of new infectious agents. Adherence to well-established biosecurity measures and acclimatization procedures decreases the likelihood of disease in growing pigs reared in multi-site systems. The use of efficacious vaccines in sows prior to farrowing and in the isowean pigs also decreases the economically negative impact of disease during the growing period.

Bibliography Allan, G. M., F. McNeilly, J. P. Cassidy, G. A. C. Reilly, B. Adair, W. A. Ellis, and M. S. McNulty. 1995. Pathogenesis of porcine circovirus: Experimental infections of colostrum-deprived piglets and examination of pig fetal material. Veterinary Microbiology 44:49–64. Allen, W. D., C. G. Smith, and P. Porter. 1973. Localization of intracellular immunoglobulin A in porcine intestinal mucosa using enzyme-labelled antibody. Immunology 25:55–70. Amass, S. 1997. The effect of wean age on pathogen removal. Nuts and Bolts of SEW Multi-site Systems, 20–32. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Amass, S. 1998. The effect of weaning age on pathogen removal. Compendium on Continuing Education for the Practicing Veterinarian 20:5196–5203. Castro, G. 1998. Personal communication. Crowe, C. K., D. L. Harris, L. P. Elliott, E. R. Wilson, and B. S. Wiseman. 1996. A possible relationship between low facility dust and endotoxin levels and improved growth rates in pigs reared by isowean. Swine Health and Production 4(5):231–236. Drum, S. S., R. D. Walker, W. E. Marsh, M. M. Mellencamp, and V. L. King. 1998. Growth performance of segregated early-weaned versus conventionally weaned pigs through finishing. Swine Health and Production 6(5):203–210. Galina, L. 1995. Possible mechanisms of viral-bacterial interaction in swine. Swine Health and Production 3:9–14. Halbur, P. 1995. Swine pneumonia: The complicating role of porcine reproductive and respiratory syndrome (PRRS). Veterinary Scope 4(1):8–11. Halbur, P. G. 1998. PRRSV interactions with Streptococcus suis and Mycoplasma hyopneumoniae. Proceedings of the Swine Disease Conference for Swine Practitioners 9–18. Harris, D. L., G. W. Bevier, and B. S. Wiseman. 1987. Eradication of transmissible gastroenteritis virus without depopulation. Proceedings of the American Association of Swine Practitioners 555–561.

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Holck, J. T., A. P. Schinckel, J. L. Coleman, V. M. Wilt, M. K. Senn, B. J. Thacker, E. L. Thacker, and A. L. Grant. 1998. The influence of environment on the growth of commercial finisher pigs. Swine Health and Production 6:141–145. Hurt, C. 1995. Summary and conclusions. In Anonymously Positioning Your Pork Operation for the 21st Century, 183–193. Cooperative Extension Service Publication, Purdue University, West Lafayette, Indiana. Klasing, K. C. 1994. Interactions between nutrition and immunity. Allen D. Leman Swine Conference. Vol. 21. 1994, 35–39 Veterinary Outreach Programs, University of Minnesota, St. Paul. Matzinger, P. 1994. Tolerance, danger, and the extended family. Annual Review of Immunology 12:991–1045. Morozov, I., T. Sirinarumitr, S. D. Sorden, P. G. Halbur, M. K. Morgan, K. J. Yoon, and P. S. Paul. 1998. A novel strain of porcine circovirus in pigs with post-weaning multisystemic wasting syndrome. Journal of Clinical Microbiology 36:2535–2541. Pijoan, C. 1997. Colonization patterns by the bacterial flora of young pigs. American Association of Swine Practitioners 463–464. Pijoan, C., and M. C. Torremorell. 1996. Colonization patterns by Streptococcus suis in young pigs. Allen D. Leman Swine Conference. Vol. 23. 1996, 194. Veterinary Outreach Programs, University of Minnesota, St. Paul. Plomgaard, J. 1998. Eradication of PRRS from the swine herd. Allen D. Leman Swine Conference. Vol. 25. 1998, 194. Veterinary Outreach Programs, University of Minnesota, St. Paul. Porter, P., and W. D. Allen. 1972. Classes of immunoglobulins related to immunity in the pig. Journal of the American Veterinary Medical Association 160:511–518. Schinckel, A. P., L. K. Clark, A. L. Grant, G. G. Stevenson, and J. J. Turek. 1996. Evaluation of the effects of immune system activation versus disease on pig growth. Allen D. Leman Swine Conference. Vol. 23. 1996, 107–112. Veterinary Outreach Programs, University of Minnesota, St. Paul. Schinckel, A. P., L. K. Clark, G. Stevenson, K. E. Knox, J. Nielsen, A. L. Grant, D. L. Hancock, and J. Turek. 1995. Effects of antigenic challenge in growth and composition of segregated early-weaned pigs. Swine Health and Production 228–234. Stahly, T. S. 1996. Impact of immune system activation on growth and optimal dietary regimens of pigs. In Recent Advances in Animal Nutrition, ed. P. C. Garnsworthy, J. Wiseman, and W. Haresign, 197–206. Nottingham University Press, Nottingham, United Kingdom. Thacker, E. L. 1998. Disease Mechanisms. An overview of how microbes cause disease. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 95–101. Thacker, E. L., P. G. Halbur, R. F. Ross, and B. J. Thacker. 1998. Potentiation of PRRSV Pneumonia by dual infection with mycoplasma hyopneumoniae. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 261. Torremorell, M., M. Calsamiglia, and C. Pijoan. 1998. Colonization of suckling pigs by Streptococcus suis with particular reference to pathogenic serotype 2 strains. Canadian Journal of Veterinary Research 62:21–26. Williams, N. H., T. S. Stahly, and D. R. Zimmerman. 1994. Impact of immune system activation on growth and amino acid needs of pigs from 6 to 114 kg body weight. Journal of Animal Science 72(supplement 2):57. (Abstract) Wiseman, B. S., D. L. Harris, and B. J. Curran. 1988. Elimination of transmissible gastroenteritis virus from a herd affected with the enzootic form of the disease. Proceedings of the American Association of Swine Practitioners, St. Louis, Missouri, 145–149.

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It is beyond the scope of this book to discuss all of the infectious diseases of pigs. I have selected nine microbial diseases that are quite common in one-site and multi-site systems worldwide. Each of the nine diseases can cause economically significant losses to a pig producer. As explained in Chapter 3, pig herds can be established free of these diseases, but depending on several factors, these diseases tend to occur commonly in all pig herds around the world. Multi-site pig production provides the opportunity to maintain freedom from disease introduction, to exclude certain infectious agents from the growing phase of production, or to eliminate infectious agents from the entire system. The separation of pig farm systems into sites and loci (particularly all-in/all-out by locus) allows producers to rear pigs free of more infectious diseases than they could in the past. The nine diseases are Glasser’s disease, mycoplasmal pneumonia, pleuropneumonia, porcine reproductive and respiratory syndrome (PRRS), pseudorabies (Aujeszky’s disease), rhinitis (including atrophic rhinitis), streptococcal meningitis, swine dysentery (SD), and transmissible gastroenteritis (TGE). The difficulty in keeping pigs free of these diseases varies. If a pig farm is free of the following five diseases, it is relatively easy to keep the causative agents out: • • • • •

Atrophic rhinitis (most herds have some degree of mild, nonprogressive rhinitis) Pleuropneumonia Pseudorabies (PRV) Swine dysentery Transmissible gastroenteritis

It is more difficult to rear pigs free of these two diseases: • Mycoplasmal pneumonia • Porcine reproductive and respiratory syndrome It is even more difficult to rear pigs free of these two diseases: • Glasser’s disease • Streptococcal meningitis 97

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It is possible to eliminate PRV, SD, and TGE from both one-site and multi-site herds without total depopulation (see Table 3.9). The Plomgaard Method can be used to eliminate pleuropneumonia, mycoplasmal pneumonia, and porcine reproductive and respiratory syndrome from multi-site isowean herds without total depopulation. Glasser’s disease and streptococcal meningitis cannot be eliminated from one-site and traditional two-site farms without total depopulation and restocking with pigs free of the causative agents. It is possible to exclude the causative agent of Glasser’s disease (Haemophilus parasuis) by isowean and the causative agent of streptococcal meningitis (Streptococcus suis) by medicated early weaning (see Table 3.2). However, exclusion does not always occur, and reintroduction after weaning is very likely with both H. parasuis and S. suis. Most producers with multi-site farms should be able to maintain freedom from the first five diseases (atrophic rhinitis, pleuropneumonia, PRV, SD, and TGE). Multi-site isowean farms should also be free of both mycoplasmal pneumonia and PRRS. It is unlikely that most herds will maintain total freedom from Glasser’s disease and/or streptococcal meningitis, but these two diseases will tend to be less severe in herds free of the other seven diseases. The methods for control of infectious diseases are often complicated by the unique set of circumstances associated with each pig production system. The following factors should be considered when attempting to apply control methods to any infectious disease: • • • • • • • • • •

facility design location of the farm with respect to other pig farms and livestock level of biosecurity precautions purpose of the enterprise, i.e., breeding stock or solely slaughter-pig production the microbial agent(s) involved in the disease process antimicrobial and vaccine usage managerial approach to introduction of new stock or genes source and type of food level of sanitation whether pig flow is all-in/all-out or continuous by room, building, locus, or site

The microbial agents and control approaches discussed in this chapter pertain to a few of the most common infectious diseases of pigs. The reader is referred to the following texts for more detailed information (Muirhead and Alexander, 1997; Straw et al., 1999; Taylor, 1999).

Glasser’s Disease Nature of the Causative Agent and the Disease Glasser’s disease is caused by a bacterium called Haemophilus parasuis. Glasser’s disease is characterized by a severe septicemia in which a large amount of pus will accumulate in the brain, the joints, and around the heart and lung, resulting in severe pericarditis, pleuritis, arthritis, and meningitis. The agent is present in most pig herds around the world. Therefore, if piglets are nursing a sow that has been previously exposed to the agent, antibodies 98

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from the colostrum protect the piglet against the symptoms of Glasser’s disease. However, some piglets suckling such immune dams will likely become infected with the agent if exposed, even though clinical signs of the disease may not occur before weaning. Haemophilus parasuis is considered an emerging respiratory pathogen of the pig. Glasser’s disease is emerging as a significant disease due to the failure of herd immunity to develop in the adult population of some herds and to the apparent possible immunesuppression (see Chapter 4, “Herd Immunity” and “Emerging Infectious Diseases”) induced by other infectious agents. The lack of herd immunity is likely due to weaning pigs at less than 21 days of age, particularly in multi-site herds. It is common in multisite herds for outbreaks of Glasser’s disease to occur in nursery or grower/finisher pigs. It would appear that in such herds, some pigs may never have received protective antibodies to the agents from their mothers or when the protective antibodies the piglet received in colostrum begin to decay, perhaps Glasser’s disease then will occur in certain pigs in the growing period. The source of the organism in such situations is apparently piglets that have been infected with the agent while nursing the sow. It is also likely that the immune-suppression induced by a combination of both PRRS virus (PRRSV) and Mycoplasma hyopneumoniae (the cause of mycoplasmal pneumonia) enhances the severity and/or occurrence of Glasser’s disease. Glasser’s disease is also quite common in newly derived SPF, MEW, or isowean herds in which the original pigs were free of the agent. Haemophilus parasuis gains entrance to such herds usually within 1 to 5 years after they have been established, and severe outbreaks of Glasser’s disease occur. The route of entry is unknown, although it is suspected that perhaps the organism is carried in by the pig caretakers or by rodents.

Transmission and Spread Haemophilus parasuis is spread from pig to pig by direct contact. It readily becomes established in the nasal cavity of the pig. Haemophilus parasuis tends to enter surgically derived or MEW-derived or isowean-derived high–health status herds rather quickly (within months to a few years) after being established. In these situations, it is not known exactly how the organism is introduced.

Diagnosis The signs and lesions of Glasser’s disease are extremely characteristic, and usually a diagnosis can be made without submission to a laboratory. However, the disease could be confused with a polyserositis disease of the joints, pericardium, and pleura caused by Mycoplasma hyorhinis. Haemophilus parasuis is readily cultured in the laboratory if samples are submitted immediately after collection. The organism will die very rapidly in specimen samples such as swabs, so samples should be submitted and set up by the laboratory within a few hours after collection. In most instances, it is important to submit samples to the laboratory and to request that the laboratory save the isolate of H. parasuis in order for an autogenous bacterin to be produced. In pigs, Haemophilus parasuis produces antibodies that are detectable by a complement fixation test. In general, serologic tests have not proven to be necessary or useful regarding diagnosis of the disease. 99

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Treatment Usually, pigs infected with Haemophilus parasuis will respond to treatment with penicillin, lincomycin, or oxytetracycline. However, if symptoms of Glasser’s disease have been present for a few hours, pigs may die even after they have been treated.

Prevention There are commercially prepared bacterins that are efficacious for the prevention of Glasser’s disease caused by H. parasuis. However, there are at least eight different serotypes of H. parasuis, and in some instances, the commercial bacterins are not protective. In such cases, it is recommended that autogenous bacterins be prepared from the isolate of H. parasuis that is present in the herd suffering from Glasser’s disease. Bacterins are usually administered to the sow 3 to 4 weeks prior to farrowing, as well as to the pigs at about 7 to 8 weeks of age. It is extremely difficult to prevent the introduction of H. parasuis into a pig farm, especially since it is not known exactly how the organism enters it.

Control Although H. parasuis can be eliminated by MEW or isowean, it appears as though this is not a fruitful objective. At present, the use of commercial or autogenous bacterins in both sows prior to farrowing and in growing piglets is the best method of control of Glasser’s disease. Furthermore, maintaining a herd free of PRRSV, Mycoplasma hyopneumoniae, and other respiratory pathogens will likely decrease the severity of Glasser’s disease.

Mycoplasmal Pneumonia Nature of the Causative Agent and the Disease Mycoplasmal pneumonia is caused by Mycoplasma hyopneumoniae. This disease is a very mild form of pneumonia, and the agent M. hyopneumoniae occurs in the vast majority of pig herds in the United States and throughout the world. When M. hyopneumoniae is the only respiratory pathogen infecting a pig, the disease is extremely mild, but the pig will exhibit a rather light, low unproductive cough. It is believed to exert a slight depression in growth rates when the organism is alone in the lungs of pigs. More importantly, Eileen Thacker has elegantly proven that the presence of M. hyopneumoniae in the lung is likely helpful in establishing other infectious agents, especially PRRSV, which leads to immune suppression and more severe forms of pneumonia.

Transmission and Spread Mycoplasma hyopneumoniae is passed from pig to pig via an aerosol of the respiratory secretions. It is readily introduced into herds by infected carrier pigs that may appear asymptomatic at the time of introduction. The organism can apparently be spread in the air between buildings and possibly between farms, but it is generally believed that a separation of buildings or farms by approximately 1–2 miles is an adequate distance to prevent spread of the organism. 100

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Diagnosis An indication of the presence of M. hyopneumoniae in lung tissue can be ascertained by necropsy of affected pigs or by examination of lungs at slaughter. The small lobes of the lung—apical and cardiac—near the heart may be affected with plum-colored lesions. Confirmation of the presence of the organism must be made by laboratory examination of the lung tissue by impression smears or the direct florescent antibody (IFA) test. Pigs infected with M. hyopneumoniae will have antibodies in their serum detectable by complement fixation and the ELISA tests. These tests are not particularly accurate on an individual pig basis, but can be very beneficial in determining if a group or herd of pigs is infected with the agent. A polymerase chain reaction (PCR) test can be used to detect the organism in nasal secretions or in tracheal/bronchial swabs.

Treatment A variety of antimicrobial compounds are available for treatment of pigs affected with M. hyopneumoniae. These include tilmicosin, tiamulin, enrofloxacin1, oxytetracycline, and lincomycin. Often the treatment for pneumonia, when M. hyopneumoniae is a causative factor, must include treatment for the other agents that can be exacerbating the infection. Medication with antimicrobials does not result in elimination of the M. hyopneumoniae organisms from previously infected pigs; however, drugs given to isowean pigs prior to infection are effective in aiding in exclusion of the microbe.

Prevention Antimicrobials can be used to prevent the symptoms of M. hyopneumoniae infection. If young piglets are treated individually with tetracycline prior to becoming exposed to the infectious agent, they will not become infected. In recent years, very effective vaccines have been developed that are quite efficacious for reducing the severity of pneumonia caused by M. hyopneumoniae. These vaccines have been shown to be economically cost effective in that the performance improvement in pigs infected with the organism helps offset the cost of the vaccines, particularly in the growing period. The vaccines have also been shown to be quite helpful when used on M. hyopneumoniae– negative gilts that are being introduced as replacement-breeding stock into M. hyopneumoniae–infected herds.

Control Eradication Programs — Until recently, total depopulation was recommended for the eradication of M. hyopneumoniae from one-site and traditional two-site farms. In 1989, Zimmermann in Switzerland was able to eradicate M. hyopneumoniae with only partial depopulation from small (approximately 20–30 sow) one-site farms. He eliminated all breeding-age animals less than 10 months of age and depopulated the nursery and finishers. Tiamulin was given to the sows in the feed and was injected into newly born piglets 1. In some countries, this drug cannot be used legally in meat-producing animals. The same footnote number occurs throughout the chapter referring to this note.

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for a 2-week period. Subsequently, Poul Baekbo in Denmark and Bjorn Lium in Switzerland have had similar success in one-site farms. In 1997, Jorgan Plomgaard was able to eliminate M. hyo from a 600-sow three-site farm by using enrofloxacin1 in a similar approach. Plomgaard’s Method was as follows: 1. Removing all females 10 months of age or less from site 1. This occurred 6 years after the introduction of M. hyo into site 1. 2. Closing site 1 to further introductions for 4 months. 3. Conducting an off-site breeding project with M. hyopneumoniae–negative replacements. 4. Depopulating site 2 (nursery production stage) and site 3 (finisher production stage). 5. Medicating sows for 14 days with enrofloxacin1 (5 gm/kg per os) and suckling piglets on 0, 7, and 14 days with enrofloxacin injectable (5 gm/kg); this 14-day medication period was only done once when negative replacements began to be introduced. 6. Simultaneously also eliminating Actinobacillus pleuropneumoniae and PRRSV (see “Pleuropneumonia” and “Porcine Reproductive and Respiratory Syndrome”). Elimination by Isowean — Mycoplasma hyopneumoniae is readily eliminated by the Isowean Principle. If the adult population has been recently infected with the organism, it appears that antibodies in the colostrum are beneficial in protecting the piglet during the suckling period. (To decrease shedding of Mycoplasma by the sow, lincomycin can be injected each day for 3 days prior to farrowing.) However, to assure prevention of infection during lactation, the piglet should be injected with enrofloxacin, oxytetracycline, or lincomycin every 3 to 5 days. In addition, for 2 to 3 weeks following weaning, it is recommended that the pigs be given tiamulin in the feed or water.

Pleuropneumonia Nature of the Causative Agent and the Disease Pleuropneumonia means that both the surface covering (pleural membrane) and the inside of the lung (pneumonia) is diseased. The main cause of pleuropneumonia in swine is Actinobacillus pleuropneumoniae (App). Other bacteria, such as Pasteurella multocida, can cause pleuropneumonia, but the disease is sporadic and less severe. In severe outbreaks of pleuropneumonia, up to 50% of nursery- or finisher-aged pigs may die of acute respiratory symptoms. In these situations, pigs may die within 4–6 hours of exhibiting respiratory distress that is characterized by coughing, abdominal breathing (thumping), and sitting on their rear legs. Near the time of death, pigs may have blood-tinged saliva and nasal secretions.

Transmission and Spread Actinobacillus pleuropneumoniae is spread via respiratory and salivary droplets. The organism does not appear to travel long distances via aerosol because it is relatively easy to prevent trans102

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mission between herds with sound biosecurity precautions. Robert Desrosiers and Camille Moore recently found five farms that may have become infected with App from non-pig sources. Jacque Nicolet has isolated App from cattle, deer, and lambs in Switzerland.

Diagnosis In general, a diagnosis is made based on clinical signs and gross lesions observed in the lungs of affected pigs. The isolation and identification of App from affected pigs with typical clinical signs and gross lesions is confirmatory for the disease. The mere isolation of App and subsequent serotyping in the absence of clinical signs and gross lesions is not necessarily confirmatory for presence of economically significant disease. There are several serotypes of App. Some serotypes have been considered avirulent. Some serotypes can be considered virulent in some countries but less virulent or avirulent in other countries. Under experimental conditions, Vibeke Sorensen in Denmark has shown that isolates cultured from herds with no evidence of pleuropneumonia can cause pleuropneumonia when susceptible pigs are experimentally inoculated with them. There have been at least three serologic tests developed for the diagnosis of pleuropneumonia in swine: complement fixation (CF), hemolysin neutralization (HN), and enzyme-linked immunosorbent assay (ELISA). Each serotype must be assayed separately in both the CF and ELISA tests. Not all serotypes have hemolysin; thus the HN test does not detect antibodies to all serotypes. Since the identical gene that codes for the hemolysin in App is also present in other bacteria, such as Escherichia coli and Actinobacillus suis, it is possible that App-negative pigs could be positive in the HN test. The interpretation of serologic test results is difficult, particularly if no clinical signs or gross lesions of the disease are present in the pigs. In some situations, pleuropneumoniafree breeding stock with serologic titers to App have been supplied to customers over a period of many years without the disease occurring.

Treatment The following medications are currently the most effective for treatment of pleuropneumonia: tiamulin, tilmicosin, and enrofloxacin.1

Prevention Commercial bacterins are produced for the prevention of pleuropneumonia. However, most bacterins have questionable to low efficacies. In some cases, autogeneous bacterins have appeared to be beneficial.

Control Eradication Programs Actinobacillus pleuropneumoniae has been eradicated from one-site and traditional two-site farms by partial depopulation, but it is a not a very reliable method. Total herd depopulation is usually required. 103

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Jorgan Plomgaard has eradicated the organism from site 1 of a three-site farm by the following procedure: 1. Removing all females from site 1 that were 10 months of age or less. This occurred 5 months after the introduction of App into site 1. 2. Closing site 1 to further introductions for 4 months. 3. Conducting an off-site breeding project with App-negative replacements. 4. Depopulating site 2 (nursery production stage) and site 3 (finisher production stage). 5. Removing App sero–negative animals from site 1 prior to introducing PRRSVnegative pregnant and open replacements. 6. Medicating sows for 14 days with enrofloxacin and of suckling piglets on 0, 7, and 14 days with enrofloxacin injectable; this 14-day medication period was only done once when negative replacements began to be introduced. 7. Simultaneously also eliminating Mycoplasma hyopneumoniae and PRRSV. Elimination by Isowean — Actinobacillus pleuropneumoniae can be readily eliminated by isowean with weaning ages from 5 to 28 days. Administration of tiamulin, enrofloxacin1, or tilmicosin to sows and piglets is recommended. Modified Multiple-site Production — Jer Geiger, assisted by Bill O’Hare, converted 11 individual 1400-sow one-site farms to all-in/all-out production. Each week they mixed weaned pigs from all breeding production stages into one nursery production stage. Mortality rates and drug costs associated with App were dramatically reduced compared to retrospective data collected prior to the pig flow conversion.

Porcine Reproductive and Respiratory Syndrome (PRRS) Nature of the Causative Agent and the Disease Porcine reproductive and respiratory syndrome is caused by an Arteriviridae virus, a type of RNA virus. The disease occurs primarily as a reproductive disorder in adults and a respiratory ailment in suckling and growing pigs. In the pregnant sow, the virus can pass through the placenta and infect the unborn piglet. These piglets may be born weak and infected with the virus. When PRRSV is first introduced into a herd, very serious reproductive and respiratory symptoms may appear. Subsequently in well-managed herds, the virus may only cause low-grade sporadic infections, particularly if replacement gilts are well acclimatized prior to breeding. As with most RNA viruses, PRRSV changes rapidly so herd immunity to one strain may not protect against infection by another strain.

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Transmission and Spread PRRSV is spread from pig to pig by direct contact, probably saliva transfer, and can be transmitted via infected placentas and stillborn piglets. Although the virus is highly infectious, it is often not particularly transmissible. That is, some strains require direct contact to transfer the infection, whereas other strains are more readily transmitted via aerosol. It is also spread venereally and has been transmitted to herds via artificial insemination. PRRSV is most often introduced into herds by infected replacement breeding stock and/or semen. Persistent infection of PRRSV — PRRSV can persistently infect pigs for over 250 days. It is not known if the virus from such persistently infected pigs is still infectious for other pigs. The work by Jorgan Plomgaard, Bill Christianson, Meritxell Donadeau, Marie Gramer, Rick Tubbs, and Bob Thompson (see “Control”) tends to indicate that persistent infections are not that common in field cases of PRRS.

Diagnosis A diagnosis of PRRS is sometimes difficult to ascertain. In early infections, the virus can be isolated or demonstrated in the blood of infected pigs by virus isolation or the PCR test. Collection of macrophages from dead or live pigs by lung lavage may be necessary to demonstrate the virus in chronically affected pigs. The IDEXX enzyme-linked immunosorbent assay (ELISA) is the most common method of serologic test used to diagnose and monitor PRRSV infection in pigs. The antibodies detectable by the ELISA test remain in the serum for a long time after initial virus infection. Modified live and killed PRRSV vaccines induce antibodies detectable by the ELISA test as well. Other serologic tests used primarily in research that measure antibody to PRRSV are serum neutralization (SN), the indirect fluorescent antibody (IFA) assay, and the immunoperoxicase monolayer assay (IPMA). Both the IFA and IPMA tests are positive very soon after initial infection with PRRSV and decrease in titer more rapidly than the ELISA tests. After viremia ceases, the ELISA tends to remain positive, while the other three tend to become negative. The IFA and IPMA can detect the same antibody. Annette Botner in Denmark believes that declining levels of antibody in the IPMA test may reflect whether a pig has stopped shedding the PRRSV. Pigs born from sows not infected with PRRSV do not become infected or have antibodies to PRRSV if no exposure to the virus occurs (Figure 5.1). Pigs born from infected immune sows will have antibodies to PRRSV but will not become infected or shed the virus if no exposure occurs post-weaning. If pigs born from infected immune sows become infected post-weaning, the pigs will likely produce antibodies to PRRSV and shed PRRSV once their maternal antibody levels

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Figure 5.1 Shedding of PRRSV in pigs with no exposure to the virus. (Modified from Christianson, 1998)

decline (Figure 5.2). Eventually, these pigs will stop shedding the virus and their antibody levels will decrease.

Treatment As with most viral infections, there is no drug treatment for the disease.

Prevention Efficacious live avirulent vaccines are available, but these are not effective against all strains of the virus. Avirulent vaccine virus also can cause respiratory disease in young piglets and reproductive problems if given at the wrong stage of pregnancy. Killed vaccines are not harmful to pigs but may not be as efficacious as avirulent live vaccines. Owners/managers of all herds, whether PRRS-infected or not infected, should only purchase PRRSV-negative breeding stock. This way, there is less chance of introducing a new mutant form of the virus into the herd. Well-managed herds, with good biosecurity practices, that are infected with PRRSV usually have few problems with clinical PRRS if care is taken to only introduce replacement stock free of PRRSV. Some infected herds appear to perform better if they use avirulent vaccines, particularly prior to breeding replacement stock. Gilt development — Gilt development refers to the process of isolating and acclimatizing gilts prior to being bred. During gilt development, gilts are prepared for breeding by (1) being exposed to and recovering from infectious agents, (2) receiving vaccinations and producing antibodies to various infectious agents, and (3) becoming sexually mature to 106

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Figure 5.2 Shedding of PRRSV in pigs exposed to the virus. (Modified from Christianson, 1998)

maximize litter size in all parities. Properly conducted gilt development aids in the management of the gilt pool and the breeding program that is essential for proper throughput of isowean pigs. PRRSV- NEGATIVE RECIPIENT HERD

— Only PRRSV-negative replacement gilts should be used. Replacement gilts that are free of PRRSV can be readily introduced at or near sexual maturity into PRRSV-negative site 1 loci after they have been isolated for a minimum of 21 days. During isolation, it can be determined if the gilts are infected with any other infectious agents not present in the recipient farm. When the replacement gilts and the recipient farm are both free of PRRSV, the acclimatization process can take place in site 1 facilities of the recipient farm. Prior to breeding, the gilts should be acclimatized for at least 21 days. During acclimatization, the gilts should be exposed to cull sows, feces, urine, and saliva from the breeding area of the site 1 loci to develop immunities against other infectious agents in the recipient farm. PRRSV- POSITIVE RECIPIENT HERD

— Ideally, only PRRSV-negative gilts should be utilized as replacements for PRRSV-positive herds. An avirulent live PRRSV vaccine administered during acclimatization can be beneficial in preventing disease due to PRRSV infection. However, since PRRSV is an RNA-type virus that readily mutates, PRRSV vaccines are not always effective in preventing mutant strains. PRRSV- POSITIVE SOURCE OF REPLACEMENT GILTS

— PRRSV-positive replacement gilts may need to be used when PRRSV-negative gilts are not available. The replacement gilts should be isolated for 21 days prior to acclimatization. During isolation, it can be 107

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determined if the gilts are infected with any other infectious agents not present in the recipient farm. The acclimatization process must take place in isolation away from site 1. The acclimatization period may need to be 60–90 days prior to breeding in order to allow time for exposure to and recovery from PRRSV present in the recipient farm. Live avirulent PRRSV vaccines can be administered to the gilts either prior to delivery or during acclimatization. During acclimatization, the gilts should be exposed to cull sows, feces, urine, and saliva from the breeding area of the site 1 farm. Breeding must not occur during acclimatization until all replacement gilts have been infected with PRRSV from the recipient herd and have recovered from the infection. If only one source farm was used for the initial stocking and it continues to be the supply herd and no new strains of PRRSV are introduced into either the source or recipient farm, a minimal problem with PRRSV can be anticipated (see Chapter 8, “Production Pyramids”). PRRSV- NEGATIVE SOURCE OF REPLACEMENT GILTS

— The replacement gilts should be isolated for 21 days prior to acclimatization. During isolation, it can be determined if the gilts are infected with any other infectious agents not present in the recipient farm. The acclimatization process must take place in isolation away from site 1. The acclimatization period may need to be 60–90 days prior to breeding to allow time for exposure to and recovery from the PRRSV present in the recipient farm. Live avirulent PRRSV vaccines can be administered to the gilts either prior to delivery or during acclimatization. During acclimatization, the gilts should be exposed to cull sows, feces, urine, and saliva from the breeding area of the site 1 farm. Breeding must not occur during acclimatization until all replacement gilts have been infected with PRRSV and recovered from the infection.

Control Eradication Programs Total depopulation, cleanup, and repopulation with PRRSV-negative breeding stock is one method of eradication; however, in some countries the PRRSV-negative replacement stock may not be available. Scot Dee has reported successful eradication in two herds without depopulation by test and removal. In these two herds, all replacement stock was PRRSV-negative for over one year and then replacements were not brought in for several months during the test and removal phase of the program. Bob Thompson and Rick Tubbs have eliminated PRRSV from a two-site isowean system without total depopulation and without testing and removal. It appeared that depopulation of the nursery and partial depopulation of the finisher was essential for this to have worked. In addition, the finisher building in closest proximity to the nursery was left empty for several months, which allowed time for the virus excretion to cease in the older finisher pigs. The animal caretakers were careful not to track the virus back from the finisher to the nursery or to site 1. 108

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Table 5.1 Three Methods of Procuring PRRSV-negative Piglets from PRRSV-infected, Unvaccinated Herds in the United Kingdom Procedure

Hysterectomies Isowean MEW

Total Batches of Piglets

Negative Batches

Success

62 34 17

57 31 16

91.93% 91.18% 94.12%

Source: Modified from Donadeu et al. (1999).

Jorgan Plomgaard in Denmark was able to eliminate PRRSV from a 600-sow three-site farm by 1. Removing all females from site 1 that were 10 months of age or less. This occurred 6 months after the introduction of PRRSV into site 1. 2. Closing site 1 to further introductions for 4 months. 3. Conducting an off-site breeding project with PRRSV-negative replacements. 4. Depopulating site 2 (nursery production stage) and site 3 (finisher production stage). 5. Removing the PRRSV sero-negative animals2 from site 1 prior to introducing the PRRSV-negative pregnant and open replacements. 6. Simultaneously also eliminating Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae. Elimination of PRRSV by MEW and Isowean — Bill Christianson and colleagues at PIC (see Donadeu et al. 1999 and Marie Gramer et al. 1998) have conclusively shown that PRRSV can be eliminated from PRRSV-positive sow farms by either MEW or isowean (Table 5.1). In some cases, MEW may be required if high levels of circulating virus are present. A weaning age of less than 8 days was used.

Pseudorabies (Aujeszky’s Disease) Nature of the Causative Agent and the Disease Aujeszky’s disease is caused by a herpesvirus that is usually referred to as pseudorabies virus (PRV). There are many types of herpesviruses. In humans, one type of herpesvirus causes cold sores, another type causes venereal disease, and yet another type causes chicken pox. Pseudorabies virus does not infect humans. The various types of human herpesviruses do not infect pigs. Pseudorabies virus can infect dogs, cattle, sheep, and certain species of wildlife, but the primary source of the virus to other pigs is the infected carrier pig. 2. Most people might think that the sero-positive animals should be removed, but Jorgan Plomgaard believed the susceptible sero-negative animals should be removed.

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All herpesviruses share a common characteristic in that after an animal or human has recovered from the initial infection and disease symptoms, the virus can continue to reside in the nerves of the body. Later, the virus can become reactivated due to stress or the exposure to ultraviolet rays, and disease can occur again. The recurrence of disease in a human who recovered from chicken pox is called shingles. The ability of PRV to reside in the nerve endings of a pig recovered from the clinical signs of Aujeszky’s disease requires that all recovered pigs be considered potential reservoirs of the virus. Swine that have never been exposed to PRV can become infected with PRV if they are mixed with pigs that had recovered from signs or infection with PRV. Pseudorabies virus can cause illness in the pig’s respiratory or reproductive tract. If the virus infects a pregnant sow, the piglet(s) can die before being born, depending upon the stage of pregnancy. Such piglets killed in utero are either born dead (stillborn) or mummified.

Transmission and Spread The virus is spread or transmitted to other pigs via respiratory and reproductive tract secretions. It can be venereally transmitted via natural service or by artificial insemination. Pseudorabies virus can travel for over 20 miles via the wind and contaminate other pig farms. Improper load-out or load-in procedures are the most common methods of virus introduction into a susceptible herd, such as when the transport vehicle either contains infected pigs or has been previously contaminated with the virus.

Diagnosis and Vaccination Very sophisticated and accurate means of diagnosis can be conducted in a properly equipped diagnostic laboratory. The virus itself can be isolated and identified or demonstrated in tissues collected at necropsy of dead piglets or adults. Based on blood testing (serum antibody levels or titers), an enzyme-linked immunosorbent assay (ELISA) is used worldwide to diagnose the disease. The ELISA was designed specifically to be used in conjunction with gene-deleted vaccines for the prevention of Aujeszky’s disease. The ELISA antigen is a protein coded for by the field or wild-type virus (the virus occurring in pigs affected with Aujeszky’s disease in farms). Thus, antibodies are produced to this protein when pigs are infected with field or wild-type PRV. Gene-deleted vaccines do not contain the gene coding for the protein used in the ELISA; therefore, pigs immunized with the gene-deleted vaccine do not produce antibodies to the protein used in the ELISA and are negative in the ELISA. Pigs immunized with a PRV gene-deleted vaccine can become infected with field or wild-type virus but usually will not show signs of Aujeszky’s disease. However, such vaccinated and infected pigs can spread the disease to other susceptible pigs, which will produce antibodies to PRV and their sera will be positive in the ELISA. In countries or provinces with eradication or control programs for PRV, pigs testing positive in the ELISA must not be sold as breeding stock.

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Prevention Immunization of sows and piglets with gene-deleted modified live PRV vaccines will prevent pseudorabies. Routinely, gilts and sows are vaccinated prior to breeding and immediately after farrowing to maximize protection during the reproductive cycle. Boars should be vaccinated twice yearly. Piglets can be vaccinated beginning around 8 weeks of age.

Control Eradication Programs If a country or region is attempting to eradicate PRV, vaccines may be used selectively, depending upon the incidence of the disease. Continual use of vaccines in infected herds will eventually result in elimination of the virus from the herd if strict biosecurity measures are followed to avoid reintroduction of the PRV. Elimination of the Virus by Isowean — Multi-site systems are ideal for producing growing pigs that are free of PRV. If all stages of production have become infected with the virus, two steps are required to begin producing PRV-negative isowean pigs: 1. Vaccinate all breeding production stage swine; do not vaccinate nursery and finisher stage pigs. 2. Wean the pigs into all-in/all-out buildings or loci that have been properly depopulated and sanitized to remove PRV; the pigs can be weaned at 21 or fewer days of age. If a source of PRV-free pigs from non-vaccinated sows free of PRV is available, these piglets can be placed with the isowean pigs in step 2 as sentinels. The sera of pigs (step 2) from PRV-vaccinated/infected sows will contain antibodies to the field virus of PRV in the ELISA; however, the sera of the sentinel pigs will test negative in the ELISA unless they become infected with PRV. Thousands of pigs have been produced by isowean from multi-site herds and used as breeding stock to either stock new units free of PRV or to supply replacements to existing PRV-negative herds in the United States.

Rhinitis and Atrophic Rhinitis Nature of the Disease and the Causative Agents Rhinitis and atrophic rhinitis are multifactorial diseases and are caused by a variety of infectious agents. Environmental factors and nutrition may play a role as well. An allergic reaction to an antigen such as ragweed pollen is one of the most common causes of rhinitis in humans; in pigs, mild rhinitis or nasal discharge can be caused by environmental factors such as dust, manure pit gases, and pollen. Atrophic rhinitis is a disease that affects the nasal turbinate bones.

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Before discussing the various causes of rhinitis, and even the different types of rhinitis that can affect the pig, it’s important to go over some of the important anatomical aspects of the nose. Inside the nose, there are several turbinate bones that are covered by a mucous membrane. The turbinates themselves are very thin and have a rich blood supply; their primary functions are to warm the air before it reaches the trachea and lungs and to serve as a filtration apparatus to keep dust particles and microbial agents from entering the trachea and lungs. Rhinitis occurs when the mucous membrane covering the turbinates becomes irritated by infectious agents or environmental factors. The membrane responds by secreting excess fluid and mucous (nasal discharge) to dilute the irritant. The factors causing the rhinitis can also irritate the eyes and ears of the pig. A common extension of rhinitis is excess lachrymal secretions, which results in staining on the outside of the face below the eye. In the normal pig, the turbinates occupy almost the entire space of the nasal cavity. The shape and size of the turbinates are determined by the bone underneath the mucous membranes. Hypoplasia of the turbinates is a failure of the turbinate bone to grow properly, particularly in pigs younger than 8 weeks of age. Hypoplasia of the turbinates is associated primarily with infection by Bordetella bronchiseptica and possibly with calcium and phosphorus deficiencies. Atrophy of the turbinate bone occurs when there is loss of bone tissue and the entire turbinate shrinks. The primary cause of atrophy is Pasteurella multocida, toxigenic type. Bordetella bronchiseptica is often the initiating infection, which can contribute to atrophy when it is present with P. multocida in the nasal cavity. The infectious causes of rhinitis are quite numerous: B. bronchiseptica, P. multocida, Haemophilus parasuis, Mycoplasma hyorhinis, and inclusion-body rhinitis virus. The main cause of atrophy of the turbinates, on the other hand, is P. multocida, toxigenic type. Nontoxigenic strains of P. multocida do not cause atrophy but do cause pneumonia when they are present in the lungs. The toxin produced by the toxigenic strains of P. multocida is one of the most potent bacterial toxins ever discovered. In pigs heavily infected with toxigenic P. multocida, the toxin circulates in the body and can cause damage to facial and leg bones and can depress the growth rate. The hypoplasia of the turbinates caused by B. bronchiseptica is usually quite mild, and the damaged turbinate often regenerates as the pig matures. In some cases of severe hypoplasia, the turbinate that regenerates is malformed and may be confused with atrophy induced by P. multocida, toxigenic type.

Transmission and Spread The infectious agents associated with rhinitis and atrophic rhinitis are spread primarily through the air. Piglets can become infected with these agents while nursing their mothers. The sources of the infectious agents are the mothers themselves and/or the pig-rearing environment. Bordetella bronchiseptica and H. parasuis can infect the young piglet as early as 3 to 8 days after birth. By contrast, P. multocida may not infect the young pig until it is 2 to 3 weeks of age. Pasteurella multocida will not infect a young pig unless the mucous membranes have become irritated by environmental factors or have been infected with

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agents such as B. bronchiseptica. If the farrowing-room environment is very clean and all-in/all-out management is in place, piglets may not become infected with these agents until after they are 3 weeks of age. Another factor influencing transmission is the level of immunity of the sow to these particular agents (see Chapter 4, “Immune Status of the Dam”). MEW and isowean pigs may be reared free of P. multocida, B. bronchiseptica, and H. parasuis, especially if they are weaned prior to 10 days of age. Pasteurella multocida and B. bronchiseptica survive well in the pig-rearing environment. Bordetella bronchiseptica, for example, can survive for up to 3 weeks in moist soil in a shaded area. All-in/all-out pig flow in thoroughly cleaned and disinfected confinement buildings readily eliminates the organisms from the pig-rearing facilities. Buildings and rooms within buildings may be readily contaminated via aerosolization of respiratory secretions from infected pigs.

Diagnosis Rhinitis itself is readily diagnosed by simple observation. The pigs will exhibit excessive sneezing, teary/watery eyes, and tear staining below the eyes. With severe rhinitis and some forms of atrophic rhinitis, the snout may appear enlarged and puffy. To confirm the presence of turbinate atrophy, it is necessary to kill the pig and perform a necropsy in which the snout is opened in such a manner that the turbinates can be observed. It is possible to use radiologic or x-ray examination, but most veterinarians consider this too impractical. Nasal secretions or a tonsil biopsy collected from live pigs or from pigs at necropsy can be used to culture bacterial infectious agents. To confirm the presence of toxigenic P. multocida, it may be necessary to collect nasal secretions and/or tonsil biopsies from several age groups of pigs on the farm, beginning with 5- to 8-week-old pigs, then 3-month-old pigs and 4- to 5-month-old pigs. The routine method of monitoring the presence of atrophic rhinitis is to conduct slaughter inspections on finisher pigs. The snouts are sawed in a cross-sectional manner at slaughter, and an index score—usually of 0 through 5, with 5 being the most severe— is applied to each snout. Severe atrophy with the majority of the snouts having scores of 4 and 5 is usually indicative of the presence of toxigenic P. multocida. Snouts that have scores of less than 3 with septal deviations (when the septum is displaced to the right or to the left) may indicate the presence of rhinitis due to B. bronchiseptica in the absence of toxigenic P. multocida.

Treatment Treatment of rhinitis and atrophic rhinitis with antimicrobials is not always effective. Injection of young piglets with either ceftiofur or long-acting oxytetracycline every 3 to 6 days during lactation may reduce the severity of toxigenic P. multocida. If the strain of B. bronchiseptica infecting the pigs is sensitive to sulfonamides, then administration via feed or water with sulfonamides may reduce the severity of rhinitis. Sulfonamides need to be given for at least 3 weeks to eliminate B. bronchiseptica.

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Prevention Due to the detrimental economic significance of toxigenic P. multocida, pig herds should be maintained free of this organism. Toxigenic P. multocida is readily eliminated by isowean technology, and it is easy to maintain one-site farrow-to-finish farms free of toxigenic P. multocida, as long as pigs that are introduced are not infected with the organism. Inactivated vaccines prepared with the toxin of P. multocida are very efficacious for the prevention of atrophic rhinitis. Inactivated vaccines prepared from B. bronchiseptica are effective for the prevention of septal deviations. These vaccines are usually administered to both sows and piglets. On the other hand, it appears extremely difficult to maintain herds free of agents causing rhinitis, such as B. bronchiseptica and H. parasuis. Herds established by SPF techniques or MEW or isowean that are free of these two infectious agents have readily become reinfected with these organisms within 1 to 5 years after initial stocking. Inactivated bacterins prepared with isolates of B. bronchiseptica and H. parasuis are efficacious in preventing signs of rhinitis. Sulfonamides in the feed and some injectable antibiotics may also be beneficial in preventing clinical signs of rhinitis caused by these organisms.

Control Eradication Programs — It has not been possible to eradicate the causative agents of rhinitis or atrophic rhinitis without total depopulation of one-site and traditional two-site farms. Elimination of Atrophic Rhinitis by Isowean — Pasteurella multocida (toxigenic strains) can be eliminated by injecting the piglets with ceftiofur every 3-5 days during lactation and isoweaning them at less than 12-14 days of age. Sows are usually immunized with a vaccine that produces antibodies to the toxin. New or depopulated herds have been stocked in this manner and, subsequently, have been successfully maintained free of the agent. Elimination of B. bronchiseptica and H. parasuis by Isowean — These agents can be readily eliminated by isowean with vaccination of the sows and appropriate medication to the piglets. A weaning age of less than 14 days is preferred. Unfortunately, pigs become reinfected with these two agents rather easily, so using isowean for this purpose seems impractical and unwarranted except for experimental purposes.

Streptococcus suis Infections Nature of the Disease and Causative Agent Disease caused by Streptococcus suis is manifest as a neurologic (meningitis) syndrome. In severe cases, up to 30% mortality rates can occur in nursery-aged pigs. There are many strains of S. suis, but serotypes 1, 1/2, 2, 9, and 14 appear to cause the most severe forms of meningitis. Several other serotypes are commonly isolated from the lung in combina114

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tion with other infectious agents, such as Mycoplasma hyopneumoniae and Pasteurella multocida.

Transmission and Spread Streptococcus suis is spread from pig to pig via respiratory or salivary droplets. The organism, which becomes established on the tonsil, gains access to the blood via the tonsil. The more virulent strains then invade the central nervous system and cause meningitis. Flies can serve as vectors for pig-to-pig transmission. Streptococcus suis can infect humans; primarily, slaughter-plant workers are affected.

Diagnosis Streptococcal meningitis is diagnosed by isolation and identification of S. suis from affected brain tissues. Isolation of S. suis from the tonsil does not necessarily mean that meningitis is occurring or is likely to occur.

Treatment The treatment of choice is injectable penicillin or ampicillin. Lincomycin, ceftiofur, and chloramphenicol1 also are effective. Antibiotics in combination with corticosteroids are recommended. Administration of drugs via feed or water often is not effective.

Prevention Bacterins have been developed but appear to have had somewhat limited success. Some practitioners believe that autogenous bacterins used both in sows and piglets are efficacious. Montserrat Torremorell and Carlos Pijoan have described a method of immunization in which the virulent strain originating from within the herd is used to inoculate each piglet at 3 days of age with live culture. These workers believe that uniform exposure of all suckling piglets may protect against disease during the waning of maternal immunity in the nursery production stage.

Control Eradication Programs — There is no effective method for eradication. Total depopulation and repopulation will not assure total absence from S. suis. Low-virulent strains of S. suis commonly infect high–health status herds but may not cause serious disease problems. Elimination by Isowean — Streptococcus suis cannot be reliably eliminated from pigs via isowean. Felicity Clifton-Hadley and Tom Alexander were able to produce pigs free of S. suis type 2 by MEW by dosing both the sow and piglets with penicillin and weaning the piglets at 5 days of age. Other workers have not always been successful in eliminating other types of S. suis from pigs by MEW or isowean. It is difficult to determine if pigs are free of the virulent strains of the organism since low- or non-virulent serotypes are found in virtually all pigs. 115

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Concurrent Infections with Other Agents — Lucina Galina showed that pigs infected with PRRSV are more likely to have meningitis when concurrently infected with S. suis, type 2. Herds that are not infected with either PRRSV or M. hyopneumoniae appear less likely to have major problems with S. suis.

Swine Dysentery and Spirochetal Diarrhea Nature of the Causative Agent and the Disease Swine dysentery is caused by a bacterium called Serpulina (Treponema) hyodysenteriae. (Recently, the name Brachyspira hyodysenteriae has been proposed for this organism.) Serpulina are spirochetal microbes that have a snake-like appearance and movement when viewed through the microscope. Swine dysentery (SD) is a severe diarrheal disease characterized by blood and mucus in the stool of acutely affected pigs. Only the large intestine is affected in SD, and millions of S. hyodysenteriae are present along the intestinal wall of the colon, cecum, and rectum of sick pigs. Pigs affected with S. hyodysenteriae may die from dehydration and electrolyte imbalance. Spirochetal diarrhea is caused by Serpulina pilosicoli and is characterized by a mild diarrhea that usually does not cause death loss. This organism also only infects the large intestine. Four main species of Serpulina can be present in the pig intestine: S. hyodysenteriae, S. pilosicoli, S. innocens, and S. succinifaciens. Serpulina pilosicoli causes a mild diarrheal disease in pigs and has a broad host range, including humans. It is unknown if S. pilosicoli produces disease in humans. Serpulina innocens and S. succinifaciens are believed to only infect pigs and do not cause disease.

Transmission and Spread Pigs infected with Serpulina but not showing signs of diarrhea can shed the organisms in their feces for several months. Susceptible pigs are readily infected by ingesting feces containing Serpulina. Serpulina survive for several days in feces at refrigerator temperature. The organisms are susceptible to drying and common disinfectants. Serpulina can infect rodents (particularly mice), and mice can carry and spread the organisms for over a year.

Diagnosis Swine dysentery causes distinct damage to the large intestine. When pigs first become sick with S. hyodysenteriae, necropsy of dead pigs can be enough to diagnose the disease. However, the differentiation of swine dysentery from spirochetal diarrhea caused by S. pilosicoli is difficult, and usually specimens (feces and/or tissues from dead pigs) must be sent to a laboratory for an accurate diagnosis. Although spirochetes can be observed readily via microscopic examination of large intestinal tissues, the various species of Serpulina cannot be differentiated by simple darkfield or phase contrast microscopy.

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Treatment and Prevention The clinical signs of swine dysentery can be reduced by treatment with several antimicrobials. The following are commonly used: lincomycin, tiamulin, and carbadox. The dinitroimadazole compounds (ronidazole1, nitroimadazole1, and ipronidazole1) are very effective, but usage of these drugs is restricted in North America. The most rapid response to therapy is by administration of the drug in the water. Drugs administered in the feed (such as carbadox1) are usually for prevention or elimination rather than for treatment of the disease. Recently, D. Hampson and co-workers in Australia have found that a low-protein diet will completely prevent the occurrence of swine dysentery without the use of antimicrobials. Experimentally, vaccines have been shown to decrease clinical signs and death loss. However, no highly efficacious vaccine has been developed that also is effective under field conditions.

Control Eradication Programs — Serpulina hyodysenteriae can be readily eradicated from pig farms without depopulation by using whole-herd medication with drugs to which S. hyodysenteriae is susceptible. Medication must be given to all pigs on the farm, and S. hyodysenteriae must be removed from the environment by a thorough sanitation program. In addition, the rodent population must be eliminated or substantially decreased. Elimination by Isowean — Pigs previously infected with S. hyodysenteriae can shed the organism for several months; therefore, suckling piglets are usually infected while nursing the dam. Either medication of the sows prior and during farrowing or medication of the piglets each day during lactation will prevent infection of the young piglets. Thus, isowean pigs can be produced free of S. hyodysenteriae.

Transmissible Gastroenteritis (TGE) Nature of the Causative Agent and the Disease Transmissible gastroenteritis is caused by a coronavirus. Piglets are very susceptible to TGE virus, which causes severe diarrhea. Every susceptible piglet less than 3 days of age that nurses a sow which has not previously been exposed to the TGE virus will die of severe diarrhea and dehydration. When 3- to 7-week-old pigs first encounter the virus, severe diarrhea will occur but less than 50% of the pigs will die if properly managed. When fully susceptible pigs 8 weeks of age or older, including adults, are exposed to the virus, they will only suffer mild to moderate diarrhea and there usually will be minimal or no death loss. The TGE virus attacks the intestinal cells lining the small intestine of the pig. The age resistance of older pigs to the virus is due to the fact that in young piglets, these intestinal cells are replaced at a much slower rate than in the older animals. In addition, the older

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animals are able to mount a greater immune response to the virus than the suckling piglet can. Once pigs in a one-site farrow-to-finish farm or a traditional two-site farm become infected with TGE virus, the virus is maintained in the herd, and it is considered a herd enzootically infected with TGE. In an enzootic herd with TGE, the pigs that have been exposed to TGE and recovered will be immune to the virus if they are re-exposed to it. Therefore, it is common that after introduction of the virus in such herds, there can be an initial loss of suckling pigs but no clinical reoccurrences of TGE for 2 to 3 years. This is especially true if no introductions of susceptible (TGE virus–negative) animals are made. However, when replacement breeding stock that has not been exposed to TGE is introduced into the breeding and gestation stage either from the finishers or from an outside source, it is common for the disease to reoccur due to a decrease in herd immunity (see Chapter 4, “Herd Immunity”).

Transmission and Spread Transmissible gastroenteritis virus is primarily spread from farm to farm by infected pigs. The virus can survive well in feces, particularly in colder climates. Transport vehicles that haul pigs but also haul grain from the field to elevators or feed mills are another source of the virus. Corn can be contaminated with TGE virus in this manner; the virus infects the pigs when they eat the corn. TGE virus can be transiently carried by birds, dogs, and possibly rodents from farm to farm. In addition, TGE virus can spread via surface water. Within the farm, the virus is spread via the feces, but also via the aerosol in respiratory secretions. In a young pig infected with TGE virus, the virus can be readily isolated from the lungs of the pig as well as the intestinal tract. However, the virus appears to cause very little damage to the lungs. Persistent Infection with TGE Virus — TGE virus has been shown to persistently reside in the tonsils of pigs for over 100 days after infection. However, after acute outbreaks of the disease in farms (see below in “Control”), previously infected pigs appear to cease transmitting the disease to sentinel pigs within a few weeks of the first exposure to the virus. Possibly, the TGE virus from persistently infected pigs is not infectious for other pigs.

Diagnosis In a pig herd that has never been exposed to TGE virus, the disease is readily diagnosed because of the high mortality rates and severe diarrhea in suckling pigs. Observation of the intestinal mucosae with a simple magnifying lens reveals stubby, shortened villi. The TGE virus can be readily demonstrated in intestinal tissues of sick pigs by the direct florescent antibody test in a laboratory. Serological tests (serum neutralization and ELISA) can be used to detect the antibody in pigs previously exposed to TGE virus. Interpretation of serologic tests for TGE virus is often complicated by the widespread occurrence of porcine respiratory coronavirus (PRCV). Pigs infected with PRCV will have antibodies that cross-react with the TGE virus serum neutralization test and the ELISA test. Some 118

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laboratories will conduct an ELISA test called the differential TGE PRCV test, which is supposed to differentiate antibodies to TGE from PRCV; however, the accuracy or specificity of these tests is somewhat in question. In herds with enzootic TGE and infection with PRCV, it can be extremely difficult to establish an accurate diagnosis due to the cross-reaction between the two viruses.

Prevention Only TGE virus–free replacement breeding stock should be introduced. Modified live vaccines that have been developed have limited efficacy. In cold climates, the virus has been introduced into herds via the feed. Feed becomes contaminated with TGE virus when grain is transported on trucks previously used to transport swine. The grain is usually used immediately to make pig feed. Producers can avoid this problem by carefully purchasing grain with regard to source and transport and by demanding that grain be stored a minimum of 3 months after transport before being used to make feed. During storage, the TGE virus will be killed. TGE virus has also been transmitted into pig farms via contaminated water and via birds.

Control Eradication Programs — TGE virus can be eliminated from one-site and traditional two-site farms without depopulation. In addition, isowean pigs can be reared free of the virus once clinical signs of the disease have disappeared and the breeding herd has become immune to virulent field virus. In an acute outbreak in one-site and traditional two-site farms, it is important that the lungs and intestinal tracts from infected piglets be saved and/or immediately inoculated into all other age groups of pigs on the farm. The purpose of this is to infect all pigs on the farm as rapidly as possible with virulent field virus. Simultaneously, replacement breeding stock, enough for a possible 5 to 6 months, should be brought into the farm and exposed to virulent virus as well. After all animals have recovered or have died from exposure to virulent virus, no replacements should then be allowed into the farm for at least 6 months, and a management program of extreme high sanitation and all-in/all-out pig flow should be instituted. As this program is followed, TGE virus will be eliminated from the farms. Elimination by Isowean — If an acute outbreak of TGE occurs in the breeding production stage in multi-site farms, it is important that the virus is spread through the entire population at site 1. In about 2 to 3 weeks after clinical signs have disappeared in site 1, isowean pigs will be weaned free of the virus. It is important that these isowean pigs are placed into nursery and finisher accommodations that are not contaminated with TGE virus. If more than one locus of production exists at site 1 (multiple sources of isowean pigs), some or most loci may not be infected with TGE virus. Some producers do not allow the TGE-positive isowean pigs to be mixed with the TGE-negative isowean pigs until the infected site 1 source is producing TGE-negative pigs. 119

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Summary The causative agents, the nature of the disease, routes of transmission, and spread of infection for nine common infectious diseases of pigs were discussed. A detailed explanation of the control and prevention of the disease, especially in multi-site production systems, was presented.

Bibliography Alexander, T. J. L. 1998. Personal communication. Alexander, T. J. L., and D. L. Harris. 1992. Methods of disease control. In Diseases of Swine, 7th ed., ed. A. D. Leman, B. E. Straw, W. L. Mengeling, S. D’Allaire, and D. J. Taylor, 808–836. Iowa State University Press, Ames. Amass, S. 1998. The effect of weaning age on pathogen removal. Compendium on Continuing Education for the Practicing Veterinarian 20:5196–5203. Baekbo, P., K. S. Madsen, M. Aagard, and J. Szancer. 1994. Eradication of Mycoplasma hyopneumoniae from infected herds without restocking. Proceedings of the 13th International Pig Veterinary Society Congress, Bangkok, Thailand, 135. Botner, A. 1998. Field experiences with PRRS and with the use of a live PRRS vaccine in Denmark. Proceedings of the Swine Disease Conference for Swine Practitioners 59–66. Botner, A., K. J. Strandbygaard, P. H. Sorensen, K. G. Madsen, and S. Alexandersen. 1997. Appearance of acute PRRS-like symptoms in sow herds after vaccination with a modified live PRRS vaccine. Veterinary Record 141:497–499. Christianson, W. T. 1998. Personal communication. Connor, J. F. 1996. PRRS control in multiple-site operations. Swine Health Summit 1996:59–61. Dee, S. A. 1998a. An overview of production systems designed to prepare naive replacement gilts for impending PRRSV challenge: A global perspective. Swine Health and Production 5:231–239. Dee, S. A. 1998b. The role of the replacement gilt in the maintenance of the PRRS infectious process. Allen D. Leman Swine Conference. Vol. 25. 1998, 96–99. Veterinary Outreach Programs, University of Minnesota, St. Paul. Dee, S. A. and T. W. Molitor. 1998. Elimination of porcine reproductive and respiratory syndrome (PRRS) virus using a test and removal process. Allen D. Leman Swine Conference. Vol. 25. 1998, 187–189. Veterinary Outreach Programs, University of Minnesota, St. Paul. DeJong, M. C. M. 1998. Personal communication. Desrosiers, R., and C. Moore. 1998. Indirect transmission of Actinobacillus pleuropneumoniae. Swine Health and Production 6(6):263–265. Donadeu, M., M. Arias, C. G.-T. M. Aguero, L. J. Romero, W. T. Christianson, and J. M. SanchezVizcaíno. 1999. Using polymerase chain reaction to obtain PRRS-free piglets from endemically infected herds. Swine Health and Production (November): (In press). Fenwick, B. 1992. Critical comparison of the serologic tests used to diagnose porcine pleuropneumoniae. Proceedings of the 12th International Pig Veterinary Society Congress, The Hague, Netherlands, 226. Fenwick, B., D. L. Harris, M. Rider, and M. Chengappa. 1996. Serologic validation of the utility of early weaning in preventing sow-to-piglet transmission of Actinobacillus pleuorpneumoniae: Production of disease-free pigs from infected breeding herds. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 482.

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Fenwick, B. W., and B. I. Osburn. 1986. Immune responses to the lipopolysaccharides and capsular polysaccharides of Haemophilus pleuropneumoniae in convalescent and immunized pigs. Infection and Immunity 54:575–582. Galina, L. 1995. Possible mechanisms of viral-bacterial interaction in swine. Swine Health and Production 3:9–14. Galina, L., C. Pijoan, M. Sitjar, W. T. Christianson, K. Rossow, and J. E. Collins. 1994. Interaction between Streptococcus suis serotype 2 and porcine reproductive and respiratory syndrome virus in specific pathogen-free piglets. Veterinary Record 134:60–64. Geiger, J. O. 1995. Control of Actinobacillus pleuropneumoniae with modified multiple-site production techniques. Proceedings of the American Association of Swine Practitioners 1995:447–451. Geiger, J. O., D. L. Harris, S. L. Edgerton, W. Jackson, J. M. Kinyon, R. D. Glock, J. F. Connor, and D. E. Houx. 1992. Elimination of atrophic rhinitis utilizing isowean three-site production. Proceedings of the 12th International Pig Veterinary Society Congress, The Hague, Netherlands, 166. Geiger, J. O., D. L. Harris, S. L. Edgerton, W. Jackson, J. M. Kinyon, R. D. Glock, J. F. Connor, and D. E. Houx. 1992. Elimination of toxigenic Pasteurella multocida utilizing isowean threesite production. Proceedings of the American Association of Swine Practitioners 45–47. Geiger, J. O., D. L. Harris, J. D. Pillen, L. Anderson, H. Hill, and H. Baker. 1991. Occurrence and elimination of pseudorabies in an isowean three-site production system. Proceedings of the American Association of Swine Practitioners 87–91. Geiger, J. O., D. L. Harris, P. J. Armbrecht, B. S. Wiseman, H. T. Hill, K. B. Platt, J. D. Pillen, J. L. Anderson, B. C. Kruse, L. A. Anderson, and H. Baker. 1991. Elimination of pseudorabies virus from three herds utilizing isolated weaning. Proceedings of the First International Symposium on the Eradication of Pseudorabies, St. Paul, Minnesota, 67. Glock, R. D. and D. L. Harris. 1993. Disease management strategies: Treat, control, or eliminate? Proceedings of the Swine Disease Conference for Swine Practitioners, Ames, Iowa, November 4–5, 1993, 1–16. Gottschalk, M. 1998. An update on Actinobacillus pleuropneumoniae and Actinobacillus suis. Proceedings of the Swine Disease Conference for Swine Practitioners, Ames, Iowa, 37–44. Gottschalk, M., and R. Bilodeau. 1995. Detecting carrier animals in herds chronically infected by Actinobacillus pleuropneumoniae: The detection of antibodies and the detection of the bacteria. Allen D. Leman Swine Conference. Vol. 22. 1995, 82–88. Veterinary Outreach Programs, University of Minnesota, St. Paul. Gottschalk, M., S. D’Allaire, J. D. Dubreuil, J. Harel, R. Higgins, M. Jacques, G.-P. Martineau, and B. Martineau-Doize. 1995. An update on Streptococcus suis infections: The University of Montreal experience. Allen D. Leman Swine Conference. Vol. 22. 1995, 89–92. Veterinary Outreach Programs, University of Minnesota, St. Paul. Gramer, M. L., W. T. Christianson, and D. L. H. Harris. 1998. Producing PRRS-negative pigs from PRRS-positive sows. Allen D. Leman Swine Conference. Vol. 25. 1998, 190–193. Veterinary Outreach Programs, University of Minnesota, St. Paul. Halbur, P. G. 1998. PRRSV interactions with Streptococcus suis and Mycoplasma hyopneumoniae. Proceedings of the Swine Disease Conference for Swine Practitioners, Ames, Iowa, 9–18. Hampson, D. J., Z. F. Fu, and W. C. Smith. 1988. Pre-weaning supplementary feed and porcine post-weaning diarrhea. Research in Veterinary Science 44:309–314. Harris, D. L. 1988. Alternative approaches to eliminating endemic diseases and improving performance of pigs. Veterinary Record 123:422–423.

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Harris, D. L., and T. J. L. Alexander. 1999. Methods of disease control. In Diseases of Swine, 8th ed., ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor. Iowa State University Press, Ames. Harris, D. L., G. W. Bevier, and B. S. Wiseman. 1987. Eradication of transmissible gastroenteritis virus without depopulation. Proceedings of the American Association of Swine Practitioners 555–561. Harris, D. L., D. Hampson, and R. D. Glock. 1999. Swine dysentery. In Diseases of Swine, 8th ed., ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor. Iowa State University Press, Ames. Harris, D. L., P. J. Armbrecht, B. S. Wiseman, K. B. Platt, H. T. Hill, and L. A. Anderson. 1992. Producing pseudorabies-free swine breeding stock from an infected herd. Veterinary Medicine (February):166–170. Joo, H., K. Direksin, C. Johnson, W. Lee, and N. DeBuse. 1998. PRRS virus serum neutralizing antibody as a measure of protection. Allen D. Leman Swine Conference. Vol. 25. 1998, 183–186. Veterinary Outreach Programs, University of Minnesota, St. Paul. Lium, B., A. Skomsoy, A. Jorgensen, B. Loe, and J. Szancer. 1992. An attempt to eradicate Mycoplasama hyopneumoniae from selected Norwegian farrowing-to-finishing herds. Proceedings of the 12th International Pig Veterinary Society Congress, The Hague, Netherlands, 300. Mengeling, W. L., K. M. Lager, and A. C. Vorwald. 1996. Alveolar macrophages as a diagnostic sample for detecting natural infection of pigs with porcine reproductive and respiratory syndrome virus. Journal of Veterinary Diagnostic Investigation 8:238–240. Mengeling, W. L., K. M. Lager, and A. C. Vorwald. 1998. Clinical effects of porcine reproductive and respiratory syndrome virus on pigs during the early postnatal interval. American Journal of Veterinary Research 59:52–55. Mengeling, W. L., A. C. Vorwald, K. M. Lager, and S. L. Brockmeier. 1996. Diagnosis of porcine reproductive and respiratory syndrome using infected alveolar macrophages collected from live pigs. Veterinary Record 49:105–115. Montaraz, J. A., M. Rider, and B. Fenwick. 1996. Evaluation of a class-specific ELISA, complement fixation and apx-1 hemolysin neutralization test to measure serum antibodies in pigs infected with Actinobacillus pleuropneumoniae. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 193. Muirhead, M. R., and T. J. L. Alexander. 1997. Managing Pig Health and the Treatment of Disease. 5M Enterprises Ltd., Sheffield, England. Nicolet, J. 1985. Haemophilus pleuropneumoniae: Bacteriology and epidemiology. Haemophilus pleurpneumoniae Compendium 7–11. Nicolet, J. 1987. Current status of the serodiagnosis of enzootic pneumonia in swine. Israel Journal of Medical Sciences 23:650–653. Nicolet, J. 1988. Taxonomy and serological identification of Actinobacillus pleuropneumoniae. American Veterinary Journal 29:578–580. Nielsen, R. 1985. Haemophilus pleuropneumoniae diagnosis, immunity and control. Haemophilus pleuropneumoniae Compendium 18–22. Nielsen, R. 1986. Serology of Haemophilus (Antinobacillus) pleuropneumoniae serotype 5 strains: Establishment of subtypes A and B. Acta vet. scand. 27:49–58. Nielsen, R. 1988. Seroepidemiology of Actinobacillus pleuropneumoniae. Canadian Veterinary Journal 29:580–582. Nielsen, R. 1993. Pathogenicity and immunity studies of Haemophilus parasuis serotypes. Acta vet. scand. 34:193–198.

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Ochiai, O., A. Yoshikazu, and K. Mori. 1997. Unification of the genera Serpulina and Brachyspira: Proposals of Brachyspira hyodysenteriae Comb. Nov., Brachyspira innocens Comb. Nov., and Brachyspira pilosicoli Comb. Nov. Microbiology and Immunology 41:445–452. Pijoan, C. 1995a. Disease of high–health pigs: Some ideas on pathogenesis. Allen D. Leman Swine Conference. Vol. 22. 1995, 16–17. Veterinary Outreach Programs, University of Minnesota, St. Paul. Pijoan, C. 1995b. Pathogenesis of Haemophilus parasius. Allen D. Leman Swine Conference. Vol. 22. 1995, 54. Veterinary Outreach Programs, University of Minnesota, St. Paul. Pijoan, C. 1997a. Colonization patterns by the bacterial flora of young pigs. Proceedings of the American Association of Swine Practitioners 463–464. Pijoan, C. 1997b. Pathogenesis of disease in SEW pigs. Pig News and Information 18:65–66. Plomgaard, J. 1998. Eradication of PRRS from the swine herd. Allen D. Leman Swine Conference. Vol. 25. 1998, 194. Veterinary Outreach Programs, University of Minnesota, St. Paul. Pluske, J. R., P. M. Siba, D. W. Pethick, B. P. Mullan, and D. J. Hampson. 1996. Reduced incidence of swine dysentery in pigs fed diets that were selected or processed to have reduced fermentation in the large intestine. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 282. Saif, L. J. and R. D. Wesley. 1992. Transmissible gastroenteritis. In Diseases of Swine, 7th ed., ed. A. D. Leman, B. E. Straw, W. L. Mengeling, S. D’Allaire, and D. J. Taylor, 362–386. Iowa State University Press, Ames. Solano, G. I., E. Bautista, T. W. Molitor, J. Segales, and C. Pijoan. 1998. Effect of porcine reproductive and respiratory syndrome virus infection on the clearance of Haemophilus parasuis by porcine alveolar macrophages. Canadian Journal of Veterinary Research 62:251–256. Solano, G., V. Rapp-Gabrielson, L. Carvalho, J. Collins, N. Winkelman, and C. Pijoan. 1996. Impact of maternal immunity on subsequent challenge of piglets with Haemophilus parasuis. Proceedings of the 14th International Pig Veterinary Society Congress, Bologna, Italy, 382. Sorensen, V. 1997. Evaluation of laboratory diagnostic assays for monitoring respiratory infections in pigs, 1–99. Denmark. Ph.D. thesis, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark. Straw, B. E., W. L. Mengeling, S. D’Allaire, and D. Taylor (eds.). 1999. Diseases of Swine, 8th ed. Iowa State University Press, Ames. Suh, D., S. Rutten, S. A. Dee, H. S. Joo, and C. Pijoan. 1998. Effect of nursery depopulation on the seroprevalence of Mycoplasma hyopneumoniae in nursery pigs. Swine Health and Production 6:151–155. Taylor, D. J. 1999. Pig Diseases. The Burlington Press (Cambridge) Ltd., Cambridge, England. Thacker, E. L. 1998. Disease mechanisms: An overview of how microbes cause disease. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 95–101. Thacker, E. L., P. G. Halbur, R. F. Ross, and B. J. Thacker. 1998. Potentiation of PRRSV pneumonia by dual infection with Mycoplasma hyopneumoniae. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 261. Thompson, R. 1998. Personal communication. Torremorell, M., M. Calsamiglia, and C. Pijoan. 1998. Colonization of suckling pigs by Streptococcus suis with particular reference to pathogenic serotype 2 strains. Canadian Journal of Veterinary Research 62:21–26. (Abstract) Torremorell, M. and C. Pijoan. 1998a. Dynamics of mucosal colonization of young pigs by Streptococcus suis. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 89.

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Torremorell, M. and C. Pijoan. 1998b. Experimental colonization of young pigs with Streptococcus suis and its effect on disease. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 90. Torremorell, M. and C. Pijoan. 1998c. Identification of epidemic strains of Streptococcus suis in swine farms. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 88. Torremorell, M., C. Pijoan, K. Janni, R. Walker, and H. Soo Joo. 1997. Airborne transmission of Actinobacillus pleuropneumoniae and porcine reproductive and respiratory syndrome virus in nursery pigs. American Journal of Veterinary Research 58(8):828–832. Tubbs, R. 1998. Personal communication. Wills, R. W., J. J. Zimmerman, K. J. Yoon, S. L. Swenson, M. J. McGinley, H. T. Hill, K. B. Platt, J. Christopher-Hennings, and E. A. Nelson. 1997. Porcine reproductive and respiratory syndrome virus: A persistent infection. Veterinary Microbiology 55:231–240. Wiseman, B. S., D. L. Harris, and B. J. Curran. 1988. Elimination of transmissible gastroenteritis virus from a herd affected with the enzootic form of the disease. Proceedings of Aamerican Association of Swine Practitioners, St. Louis, Missouri, 145–149. Zimmerman, J., K. J. Yoon, G. Stevenson, and S. A. Dee. 1998. PRRS Compendium, 1–128. National Pork Producers Council, Des Moines, Iowa. Zimmermann, W. 1990. Experiences in the EP sanitation programme to eradicate EP. Tierarztl Umshau 45:556–562.

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Multi-site isowean pig production systems originated in 1988 to reduce the impact of disease and to minimize risk for breeding stock production. Subsequently, commercial slaughter-pig producers became aware that pigs reared in this manner are more efficient in gaining weight and have more lean protein in their carcasses. The higher input costs associated with multi-site production are more than offset by increased profits (Figures 6.1, 6.2, 6.3) due to improved feed efficiency and lean gain. Table 6.1 contains the break-even analyses for three-site farms and a high-performing one-site farm. Consistent production performance for maximal profits in a multi-site system requires a far more disciplined management approach than for one-site and traditional two-site farms. All-in/all-out pig flow is required to maximize efficiency in multisite systems. All-in/all-out flow is more demanding of management than continuous pig flow and certain tasks must be done daily, without exception.

Figure 6.1 Net income from a three-site (single-source, single-locus), 2000-sow system, CRB Farm, near Columbus, Nebraska. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

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Figure 6.2 Profit per head of slaughter pigs sold per year from a three-site (single-source, single-locus), 2000-sow system, CRB Farm. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

Figure 6.3 Percent return on original cash equity of a three-site (single-source, single-locus), 2000sow system, CRB Farm. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

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Table 6.1 Break-even Analyses of Three-site Farms and a One-site Farm Three-site (Single-source, Single-locus) Farms

One-site Farm

Farm A

Farm B

Farm C

Average

Total

Feed Cost Wages/Bonus/Benefits Drugs/Vet Services Utilities Supplies Repair/Maintenance Ground Maintenance Lagoon Maintenance Fuel Trucking Management Pro. Fees Insurance Taxes Miscellaneous Net Breedstock

$22.58 $3.51 $1.22 $1.16 $0.38 $0.24 $0.11 $0.15 $0.00 $1.48 $1.28 $0.17 $0.61 $0.48 $0.07 $1.33

$22.96 $3.65 $0.53 $1.31 $0.31 $0.17 $0.05 $0.22 $0.02 $0.82 $1.28 $0.16 $0.41 $0.35 $0.03 $1.32

$22.90 $4.23 $0.89 $1.36 $0.47 $0.17 $0.10 $0.02 $0.02 $1.33 $1.27 $0.32 $0.55 $0.39 $0.01 $1.30

$22.81 $3.72 $0.85 $1.27 $0.37 $0.20 $0.08 $0.15 $0.01 $1.17 $1.28 $0.20 $0.51 $0.41 $0.04 $1.32

$26.57 $4.68 $2.07 $1.28 $0.52 $0.95 $0.00 $0.27 $0.00 $1.14 $1.53 $0.35 $0.94 $0.58 $0.05 $1.58

Direct Cash Expenses Less Feeder Pigs Slaughter Prem. Misc. Income Inventory Adjust.

$34.77

$33.59

$35.33

$34.39

$42.51

$0.15 $3.75 $0.08 $0.16

$0.22 $3.44 $0.04 $4.18

$0.00 $3.73 $0.04 $5.11

$0.15 $3.61 $0.05 $2.94

$1.71 $3.26 $0.07 $2.11

Breakeven Before Debt Plus Interest Principal

$30.63

$25.71

$26.45

$27.63

$35.36

$1.81 $4.62

$4.91 $3.35

$4.58 $3.54

$3.73 $3.85

$1.17 $2.74

$37.06 2100 5106

$33.97 2500 5662

$34.57 1250 5308

$35.21 1950 5387

$39.87 500 4025

Breakeven Including Debt Number of Sows Lbs. Pork Per Sow

Source: Gary Gausman, Sand Livestock, Columbus, Nebraska, 1998.

Multi-site isowean systems allow the specialization of workers for the various labor components of production, including certain types of repetitive tasks. On one-site and traditional two-site farms, workers usually must do a variety of different tasks, often in the same day. Owners and managers are urged to consider the policy decisions discussed in this chapter carefully before creating a multi-site system. They may find multi-site production to be much more inflexible managerially than in one-site and traditional two-site farms. The management of multi-site isowean systems is discussed in Chapter 7.

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Production and Financial Targets A combination of production and financial targets are used to monitor modern porkproduction farms (Tables 6.2 and 6.3). Financial efficiency is measured by calculations for return on assets (ROA) and return on equity (ROE). Thus, every stage of production and subsystem on the farm is included in determining whether financial targets are being met. As explained by Dennis DiPietre and co-workers, the DuPont Equation is used to diagnose and address substandard performance. Production and financial influences on the three components of ROE are: 1. Asset management: Wean-to-service interval; mortality rates by age group; nonpregnant sow days; average daily gain; pigs per litter born; pigs per sow per year; age of weaning; days in the nursery; market weight; cull rates; and farrowing rate.

Table 6.2 Financial Performance Measures Liquidity

Target

Working Capital Current Ratio Working Capital/Gross Revenue Working Capital/Sow

$ >1.50 >20% >$400

Solvency Total Equity Term Debt/Equity Owner Equity Adjusted Total Debt/Equity

$ <60% >50% <150%

Profitability Net Income Return on Equity (ROE) Return on Assets (ROA) Operating Profit Margin Net Profit Margin

$ >15% >10% >9% >6%

Coverage (Repayment Capacity) Capital Debt Retirement Capacity (CDRC) Interest Coverage

>150% >4.00

Financial Efficiency Asset Turnover Ratio Labor Costs/Lb Produced Depreciation Costs/Lb Produced Interest, Lease & Rent Costs/Lb Produced Feed Costs/Lb Produced (3-year Average) Total Cost/Lb Produced (Breakeven)

>0.90 <$4 <$4 <$5 <$22 <$40

Source: Modified from DiPietre, Fuchs, and Tubbs, 1997.

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2. Expense management: Labor expense; depreciation; feed expense; feed efficiency; market price; percent lean; average backfat; and sort loss. 3. Debt management: Working capital; current ration; working capital/gross revenue; working capital/sow inventory; total equity; term debt/equity; total debt/equity; and interest expense. Overemphasis on production targets can have a negative impact on profitability. For example, a high herd inventory of breeding animals can achieve the target of pounds of pork produced but increase the cost of production disproportionately. However, reliance on a few financial indicators alone without monitoring production targets can be misleading and make it difficult to diagnose low profitability.

Table 6.3 Production Performance Measures Production Efficiency

Target

Breeding/Gestation Wean-to-service Days Nonproductive Sow Days Breeding Herd Mortality Cull Rate Average Herd Parity (in litters)

<7 <50 <3% <35% <3%

Farrowing Farrowing Rate Pigs Born Alive/Litter Pigs Weaned/Sow/Year Pre-weaning Mortality Litters/Sow/Year

>85% >11 >23 <10% >2.40

Nursery Average Age at Weaning (in days) Days in Nursery Average Daily Gain Nursery Feed Conversion Nursery Death Loss (includes culls)

<15 <40 >1.00 <1.65 <2.5%

Finish Average Daily Gain Finish Feed Conversion Finish Death Loss (includes culls)

>1.65 <2.90 <1.5%

Whole Herd Feed Conversion Carcass Yield Average Percent Lean Sort Loss/CWT

>75% >52% <$1.00

Source: Modified from DiPietre, Fuchs, and Tubbs, 1997.

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Table 6.4 Costs of Production ($/cwt) of Five Pork Production Systems 1200-sow Three Site

600-sow Three Site

9.19 5.53 3.84

9.19 5.53 3.84

9.81 5.89 4.10

9.81 5.89 4.10

10.72 6.45 4.49

18.56

18.56

19.80

19.80

21.66

Herd Health Utilities Marketing Miscellaneous Mortality Disposal AI Costs

.51 1.71 1.00 .21 .03 .04

.51 1.71 1.00 .21 .03 .04

.53 1.78 1.00 .22 .04 N/A

.55 1.68 1.00 .23 .04 N/A

.58 1.79 1.00 .24 .06 N/A

TOTAL DIRECT

22.07

22.07

23.37

23.29

25.33

Market Inventory Breeding Inventory Equipment Buildings Land Labor Management

.04 1.59 4.04 2.67 .02 2.06 1.39

.40 1.66 4.53 2.79 .03 2.84 1.39

.44 1.20 5.66 2.67 .05 3.86 1.38

.51 1.48 6.84 2.86 .07 4.11 1.38

.72 1.73 9.27 3.70 .05 5.70 1.38

12.17

13.64

15.26

17.25

22.55

$34.25

$35.72

$38.63

$40.54

$47.88

N/A

+$1.47

+$4.38

+$6.29

+$13.63

Corn Soybean meal Other Feed TOTAL FEED

TOTAL INDIRECT TOTAL COSTS Costs vs. 1200 Sow

300-sow Three Site

150-sow Three Site

150-sow One Site

Source: Modified from Hurt, 1995.

Multi-site Production Systems Multi-site isowean pig production is not for everyone. Due to the variety of opportunities for entering pork production, no one blueprint fits all situations. All pork producers, regardless of size, can utilize multi-site production. Based on projections by Purdue University, the costs of production of various types and sizes of operations are presented in Table 6.4. Available capital can limit the number of sows at the entry level, but opportunities for small- to medium-sized producers to expand via multisite technologies should be pursued. Table 6.5 identifies the key technologies that are available to producers to increase profitability, their impact on financial return, and their ease of implementation by producers. Major mistakes made by small- to medium-sized producers are the failures to manage leverage and to reinvest in their operations to gain the advantage of scale (i.e., spreading the cost of production over larger numbers of animals produced). 130

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Table 6.5 Ranking of Technologies by Returns and Ease of Implementation Rank

1 2 3 4 5 6 7 8

Technology

Tested On

Impact $/cwt

Isowean/AIAO Genetics-Production Throughput Genetics-Revenue Split Sex/Phase Feeding All-In/All-Out Network Selling Network Buying

150 low technology 150 low tech vs 1200 150/300 vs 600/1200 150/300 vs 600/1200 150 low technology 150 low technology Judgment onlye Judgment onlye

4.73 3.38 3.09 2.24 1.79 .73 .75 .70

Ease of Impact $/head Adoptionf

11.59 8.28a 7.57b 5.48c 4.39 1.79d 1.83 1.72

7 3 8 4 1 2 5 6

aEstimated impacts of genetics on feed efficiency, pigs/litter, and fixed costs. bEstimated as 30% of difference in costs for breeding inventory, buildings, equipment, labor, and management costs. cRevenue impact of improving from 150/300 level to 600/1200 level at $45/cwt. dImpact of implementing AIAO by itself, without Isowean. The impact for Isowean/AIAO on the first line includes both

Isowean and AIAO. eBased on human judgment only. fEase of adoption by the producer is estimated on a scale of 1–8, with 8 being the most difficult. Source: Modified from Hurt, 1995.

Multi-site systems can provide traditional farmers with opportunities to add an enterprise and to diversify their farming operation by owning and operating only one stage of production (site 1, 2, or 3). Owning and managing one stage of production in diversified farming operations can be more advantageous than operating a complete farrow-tofinish one-site or two-site traditional farm. In 1992, Gordon Spronk and Gerald Kennedy started the Pipestone three-site (single-source, multi-loci) system, where producers can have joint ownership of the site 1 sow farm, which is under a central management team. Each owner then can own and manage his own site 2 and/or site 3 production loci. Hugh Dorminy at Cargill developed the Pork Works three-site (multi-source, multi-loci) system, where farmers purchase pigs from site 2 loci and place them in their own site 3 finisher buildings. The farmer has the option of “locking in” feed cost and slaughter-pig price at the time of purchase of the site 2 pigs.

Choosing a Multi-site Isowean System When choosing the type of system for pork production, one should consider many factors, including: 1. 2. 3. 4. 5. 6.

Size of the operation. How rapidly the business should grow. Ownership of land, buildings, transport vehicles, and pigs. Human resources. Nature of the business (breeder, slaughter-pig producer, or both). Type of producer (farrow-to-finish, farrow-to-isowean, farrow-through-nursery, nursery only, finish only, or vertical integrator). 131

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7. 8. 9. 10.

Zoning laws and restrictions Other business(es) owned. Waste management and environmental stewardship. Availability and cost of feed.

Some of these factors are addressed in Chapters 7 and 8; others are outside the scope of this book. Ideally, single-source isowean pigs should be placed in a building on an all-in/all-out by locus basis and have a minimum of spread in weaning age per site. For a three-site (singlesource, multi-loci) system, this requires a large number of sows (5000+). The NurFin isowean system needs fewer sows (approximately 2500) and provides the opportunity for all-in/all-out by locus wean-to-finish buildings of approximately 1000-head capacity each. Also see “Rearing System.”

Various Multi-site Systems Three-site (single-source, multi-loci) production probably is the ideal system design (see Figure 2.9). This system maximizes pig performance because pigs are weaned into an allin/all-out building on a separate locus each week. In some systems that wean each day, an all-in/all-out building on a separate locus is utilized each day. When moved from the nursery, pigs are placed in one or two finisher buildings (usually with no more than 1000 finisher-pig spaces) located on a separate locus that is well isolated and is separated from other finisher buildings. When moving pigs from the nursery to the finisher, pen integrity should be maintained. This minimizes the social disruption brought on by mixing pigs from different pens, the variation in age within a building, and the chance of lateral introduction of infectious agents and microbial antigens from older pigs in other nurseries. Performance of pigs can be negatively affected by a wide variation of age within a pen, building, or locus. Three-site (single-source, multi-loci) systems require a large sow population (5000–10,000 sows) at stage 1 in order to minimize capital costs per pig produced for all nursery and finisher sites and locations. Three site (multi-source, multi-loci) production (see Figure 2.11) allows the co-mingling of weaned pigs from several site 1 sow farms. The advantages to this approach are that sow farms can be smaller and the isowean pigs can be produced at several different locations. A disadvantage is that the occurrence of disease in one sow farm can cause a disruption of performance in the weaned pigs from the other sow farms unless the diseased pigs are diverted away for a time. A three-site (single-source, single-locus) farm built in 1988 was the first type of modern multi-site system in the world. Since then, several farms with a similar design (Figures 1.3, 2.4, 2.5) have been built. The most common size is 2000–2500 sows, but recently farms have been built with 10,000 sows. Figures 6.4–6.8 illustrate the number of pigs sold/sow/year, pounds of pork/sow/year, whole herd feed conversion, wean-tofinish death loss percentage, and profit per slaughter pig produced from six three-site (single source, single locus) systems in 1997. These farms, built between 1988 and 1995, had a total of 12,795 sows; the sow herds ranged from 1345 to 2660 sows. The weaned pigs for each farm were from a single source and were composed of the same genetic stock, 132

6. Policy Decisions and Opportunities

Figure 6.4 Pigs sold per sow per year from six three-site (single-source, single-locus) farms with identical management and genetics, 1997. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

Figure 6.5 Pounds of pork sold per sow per year from six three-site (single-source, single-locus) farms with identical management and genetics, 1997. The average output from 12,795 sows was 5190. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

133

Multi-site Pig Production

Figure 6.6 Whole-herd feed conversion per year from six three-site (single-source, single-locus) farms with identical management and genetics, 1997. The average whole herd feed conversion was 2.92. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

Figure 6.7 Wean-to-finish mortality rate per year from six three-site (single-source, single-locus) farms with identical management and genetics, 1997. The average mortality rate was 1.86%. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

and the farms were managed by the same company. In most cases, in three-site (singlesource, single-locus) production, the nursery is composed of one or two buildings on one locus and several separate finisher buildings on another locus (see Figures 1.3, 2.4, and 2.5). Pig flow is all-in/all-out by room at the nursery and all-in/all-out by building at the finisher loci. 134

6. Policy Decisions and Opportunities

Figure 6.8 Profit (loss) per head sold to slaughter per year from six three-site (single-source, singlelocus) farms with identical management and genetics, 1997. The average profit was $17 per head for the three-site farms and $7 for the average U.S. swine herd. (Tim Cumberland, Sand Livestock Systems, Columbus, Nebraska, 1998)

Table 6.6 Nursery Performances of Isowean Pigs from Three Multi-site Production Systems Three Site (Single Source, Single Locus)

Number Mortality Start age (days) Start weight (lb) End age (days) End weight (lb) Weight gain (lb) ADG (lb/day)

Three Site (Multi-source, Single Locus)

15.479 0.85% 16.26 11.35 74.30 68.09 56.74 0.977

39.468 3.71% 16.00 11.03 73.24 57.40 46.37 0.806

Three Site (Multi-source, Multi-loci)

49.306 2.5% 15.20 11.05 74.45 67.00 55.95 0.944

Source: Modified from Dufresne, 1995.

Three-site (multi-source, multi-locus) production (see Figure 2.10) allows stage 1 farms to have fewer sows. A major disadvantage of three-site (single or multi-source, single locus) production is that once the nursery has become contaminated with a economically significant pathogen and/or performance deterioration has occurred, total depopulation of each locus at sites 2 and 3 may be necessary. The nursery performances of pigs in three-site (single source, single locus), three-site (multi-source, single locus), and three-site (multi-source, multi-loci) systems are given in Table 6.6. These data illustrate the production performance advantage of all-in/all-out by locus. Finisher performance and financial comparisons of pigs in traditional two-site (multi-source, single locus), three-site (multi-source, single locus), and three-site (single source, single locus) systems are given in Table 6.7. By 135

Multi-site Pig Production

Table 6.7 Comparison of Production Costs and Net Income Gains of Slaughter Pigs from Two Types of Three-site Production Systems with Slaughter Pigs from a Traditional Two-site System Unit

Head

Wt. In (lb)

Wt. Out (lb)

Days

Per Head Cost

Mortality Rate

F/C

Gain/Day (lb)

Cost/lb Gain

TRADITIONAL TWO SITE (Multi-source) sls old 32153 1993 @$2.21/bu

41.78

228.00

133

$49.46

7.55%

3.45

1.40

$0.250

Average Total

41.78

228.00

133.00

$49.46

7.55%

3.45

1.399

$0.250

32153 THREE SITE (Multi-source, Single Locus)

sls ISO 1994 @2.43/BU Average Total

32628

46.50

230.10

129

$47.20

5.71%

3.22

1.42

$0.258

46.50

230.10

129.00

$47.20

5.71%

3.22

1.40

$0.258

4.72

2.10

–4.00

($2.26)

–1.84%

–0.23

0.02

$0.01

$0.95

$0.99

32628

Difference Dollar Savings Total

$3.56

CRB NCP TSP SLS NEW

43,372 6,478 33,437 6211

Average Total

89,498

@same corn price

$1.62

THREE SITE (Single Source, Single Locus)

Difference Dollar Savings Total

$17.58

40.70 54.30 55.80 38.61

234.50 242.40 250.20 232.18

113 108 105 136

$41.50 $40.61 $41.18 $46.39

$1.50% 0.90% 0.93% 3.44%

2.73 3.01 2.85 3.15

1.71 1.73 1.86 1.34

$0.215 $0.218 $0.209 $0.240

47.18

240.78

111.25

$41.66

1.38%

2.82

1.742

$0.215

0.68

10.68

–17.75

($5.54)

–4.33%

–0.40

0.32

($0.0433)

$4.80 $45.00

$4.39 $0.09

$8.38

/CWT /Day X2.75 Turn Source: Gary Gausman, Sand Livestock, Columbus, Nebraska, 1998.

contrast, as discussed in Chapter 4 (Table 4.6), Gonzalo Castro in Chile and Steve Drum and his colleagues in the United States have found small differences in performance between single-source (traditional two-site) feeder pigs and isowean pigs. The management practices and health status of pigs may account for these differences. Two-site isowean, two-site isowean on-site, two-site isowean off-site, and outdoor isowean production (see Figures 2.13–2.15) are particularly applicable to expansion and renovation of existing production systems. The projected performance of an existing operation that uses continuous flow production changing to all-in/all-out production is given in 136

6. Policy Decisions and Opportunities

Table 6.8 Predicted Production Performances on a Whole-herd Basis by Converting from Continuous Flow Throughput to All-in/All-out Production on One Site and to Three Approaches to Isowean Production Production Parameters

Baseline (continuous flow)

AIAOa

Isowean1b

Isowean2c

Isowean3d

120 20 1564 47 664 25 2.36 9.0 21.20 117 14,079

120 20 1564 47 664 25 2.36 9.0 21.20 117 14,079

120 11 2086 54 845 25 2.47 8.2 20.24 143 17,103

120 11 2086 93 966 25 2.16 9.0 19.43 156 18,771

120 17 1825 50 765 25 2.39 9.0 21.48 137 16,425

6.50 8.42 19.82 13,163 13 241 1.22 207 3.21

3.25 8.71 20.51 13,621 13 241 1.39 183 2.99

2.50 8.00 19.73 16,675 8 241 1.54 162 2.82

2.50 8.78 18.94 18,302 8 241 1.54 162 2.82

2.50 8.78 20.94 16,014 11 241 1.55 165 2.84

3.50

3.34

3.23

3.24

3.20

Breeding herd Farrowing capacity (crates) Weaning age (days) Litters per year Nonproductive sow days Average sow inventory Replacement rate per litter (%) Litters per sow per year Pigs weaned per litter Pigs weaned per sow per year Pigs weaned per crate per year Pigs weaned per year Nursery and grower-finisher Mortality % Pigs sold per litter Pigs sold per sow per year Pigs sold per year Weaning weight (lb) Slaughter weight (lb) Average daily gain (lb) Days to market Feed:Gain Whole operation Feed:Gain Source: Modified from Lawrence, 1996. aAll-in/all-out on one site. bWeaned at 11 days; bred on first heat. cWeaned at 11 days; bred on second heat. dWeaned at 17 days; bred on first heat.

Tables 6.8 and 6.9. It was assumed that this change could be done managerially without capital input. Tables 6.8 and 6.9 also illustrate the production and financial impact of utilizing isowean technology rather than continuous flow or all-in/all-out production. The implementation of isowean technology required that additional nursery and finisher facilities be built or leased off-site. Recently, Steve Drum and Will Marsh projected a financial advantage in converting a one-site farm to a three-site farm (see Figure 2.7). NurFin isowean production (see Figures 2.16 and 2.17) originated in 1993 in discussions at Oakville Feed and Grain in Oakville, Iowa, between Bob McCulley and Joe Connor. Since 1993, several farms built in the midwestern United States have used this concept. 137

Multi-site Pig Production

Table 6.9 Predicted Average Cash Flow Costs and Returns (in $ per Head Sold to Slaughter) on a Whole-herd Basis by Converting from Continuous Flow Throughput to All-in/All-out One-site Production and to Three Approaches to Isowean Production

Total revenue Feed costs Operating costs Labor costs Principal & interest (P&I) Cash cost Net cash flow Cash after P&I

Baseline (continuous flow)

AIAOa

Isowean1b

Isowean2c

Isowean3d

115.47 57.52 27.08 7.57 23.54 115.71 23.30 –0.24

115.32 53.67 24.27 7.31 23.60 108.85 30.07 6.47

115.75 53.45 25.64 7.60 23.72 110.41 29.06 5.34

115.22 53.56 23.95 7.92 23.74 109.17 29.79 6.05

115.29 51.89 23.97 7.16 23.73 106.75 32.27 8.54

Source: Modified from Lawrence, 1996. aAll-in/all-out one-site production. bWeaned onto a separate locus at 11 days; bred on first heat. cWeaned onto a separate locus at 11 days; bred on second heat. dWeaned onto a separate locus at 17 days; bred on first heat.

The NurFin buildings are designed as finishers that, with slight modifications, can house weaned pigs. The modifications include supplemental heat during winter, an adjustable pen design so the pen size can be expanded as the pigs grow, and nipple waterers appropriate for young weaned pigs. Nursery/finisher space is underutilized when newly weaned pigs are initially placed in a NurFin building (see Figure 2.18). The advantages of NurFin isowean are lower transport costs, less stress due to moving pigs from a nursery to a finisher building, fewer sites to develop (if all NurFins are placed on one locus), and more isolated all-in/all-out pig flow (if NurFins are placed on separate loci).

Phased Construction of a Three-site (Multi-source, Multi-loci) System A fully operational and mature three-site system calls for a maximum age range of 5–7 days in the groups of pigs in all-in/all-out nursery and finisher loci. However, during the start-up of such systems, nursery and finisher facilities can be constructed simultaneously while pigs are being produced, which results in earlier cash flow income. As illustrated in Figure 6.9, isowean pigs can fill a nursery over a 2–3 week period until adequate nursery accommodations have been built for all-in/all-out production on a weekly basis. Phase one (single source) consists of one sow farm on one locus with four nursery loci to be filled with pigs every 2 weeks. Phase two (multi-source) includes the addition of a second locus to site 1 and four more loci to site 2. The 15th and 16th finisher buildings are filled for the first time 4.5 months after the first pigs are farrowed.

138

6. Policy Decisions and Opportunities

Figure 6.9 Three-site (multi-loci) system phased construction.

139

Multi-site Pig Production

Figure 6.10 Conversion of a three-site (single-source, single-locus) system to a threesite (multi-source, multi-loci) system.

Converting from Three-site (Single-source, Single-locus) Systems to Three-site (Multi-source, Multi-loci) Systems Several three-site (single-source, single-locus) systems can be combined into one large three-site (multi-source, multi-loci) system (Figure 6.10). The advantage of this conversion is all-in/all-out nursery and finisher pig flow rather than continuous pig flow. A disadvantage is the multiple sourcing of isowean pigs from several loci of sow farms at site 1.

Number of Pigs per Site and Future Expansion Multi-site production is a powerful tool for environmental stewardship and the future expansion of an operation. The placing of too many pigs on one location has many pitfalls. These include the creation of excessive odors that are offensive to neighbors; difficulty in proper manure disposal; difficulty to expand at that location (particularly if a onesite farrow-to-finish system); and increased financial risk should depopulation due to disease be required. Strict adherence to a three-site (multi-source, multi-loci) or a NurFin isowean (multi-loci) system offers the most opportunities and security for controlling disease. Placement of 2000–3000 sows per site in stage 1 farms is optimal. Isowean pigs can be procured from two or three loci (4000–6000 sows total) on a weekly basis or less and grown out in all-in/all-out by locus in nurseries, finishers, or wean-to-finish buildings. Creation of multi-site systems in this manner minimizes the pitfalls and allows expansion of the system over time (Figure 6.10). 140

6. Policy Decisions and Opportunities

Figure 6.11 Pounds of pork produced and the number of hog farms in the United States. (United States Department of Agriculture, Economic Research Service)

A consistent historical worldwide trend in agriculture has been fewer but larger farming operations (Figure 6.11). The pounds of pork produced in the United States remains rather constant, but the number of farms producing pigs keeps dropping dramatically each year. In some countries, societal and political agendas include attempts to slow the rate of this trend and to blame the trend on corporate agriculture. Maintaining a substantial rural population in towns and villages has certain esthetic and economic advantages. When done properly, multi-site isowean systems can provide an economic stimulus to rural communities and allow various types of individuals with a variety of financial assets and educational backgrounds to make significant contributions to pork production and to their communities. It is possible for large-scale multi-site production systems to be environmentally friendly and thus assist in the maintenance of a rural population base.

Freedom from Disease Owners and senior managers often underestimate the capital requirements, operational costs, and personnel needed to avoid financial risks associated with the occurrence of disease. Pig herds should originate and be maintained with pigs of as high a health status as possible. Tom Alexander of Cambridge University in England once said, If we keep pigs to provide meat for people to eat and to make a profit for ourselves, we have a need and a responsibility to keep them free from disease and as healthy and contented as possible 1. 2. 3. 4.

for humanitarian reasons: pig welfare. so that the meat is fit to eat: free of drug residues “and human pathogens.” for optimum productivity to give maximum profitability. to minimize unpredictable risks and unbudgeted financial costs. (Alexander, 1987)

141

Multi-site Pig Production

In the ideal multi-site isowean system, each all-in/all-out production locus should be located approximately 1–2 miles from another locus or other pig production facilities. Obviously, this is not always possible. However, for breeding stock production, this degree of separation between the various stages of production and other producers is essential to prevent lateral spread of infectious agents. In some situations, 1–2 miles is not always enough separation to prevent disease transmission. Biosecurity measures and disease prevention measures will be discussed in greater detail in the next section and in Chapter 7, “Disease Breakdowns,” and Chapter 8, “Biosecurity.” For a more thorough discussion of these topics, the reader is urged to review the 1998 paper by Jose Barcelo and Enric Marco of Barcelona, Spain.

Basic Essentials Before starting up a new pig operation, owners and senior managers need to make basic policy decisions about: 1. 2. 3. 4. 5. 6. 7. 8.

Health status of breeding stock. Genetics. Source of breeding stock. Location. Rearing system. Transport of pigs. Building design and materials. Food safety and pork quality.

(Chapter 7 is about the actual management of an ongoing multi-site isowean production system.)

Health Status of Breeding Stock The most common route of vertical infectious-agent transmission is via the breeding stock introduced into the farm. Pig herds should be established with animals of as high a health status as possible. Due to a lack of forward planning, new or repopulated herds are often stocked with pigs of inferior health status. Ideally, orders for breeding stock should be placed prior to reproductive conception of the actual pigs to be delivered. When possible, herds should be stocked with pigs free of diseases that cause major production losses. Production losses are determined by death loss per age group, cost of drugs and vaccines, and pig performance. Measurements of pig performance include reproductive productivity, mortality rates by age group, growth rate of growing pigs, and feed efficiencies of growing pigs and the entire herd. Performance criteria are listed in Table 6.3. The complexity of excluding diseases can be considered in three general categories: international/national, the breeding stock supplier, and the commercial producer (Table 6.10). In practical terms, the category a specific disease is placed in depends on the country, the region, and the policy of each breeding stock company. Both commercial and breeding stock supply herds are likely to be afflicted with most of the diseases listed under 142

6. Policy Decisions and Opportunities

commercial producer in Table 6.10. The severity of these diseases, which depends heavily on management practices, often can be readily controlled by all-in/all-out throughput, good sanitation, and, for some diseases, vaccines. Internal parasites and some bacterial infections require administration of drugs as therapy or for prevention. Not all breeders are able to supply pigs free of all the diseases listed under breeding stock supplier in Table 6.10. It may be foolish of a buyer to demand freedom from a disease that will readily enter his herd from neighboring farms or via replacement stock. By matching the health status of the source farm with the health status of the recipient farm, the breeding-stock supplier and the buyer can work together to ensure that no new infectious agents are introduced into the buyer’s herd. Thus, for maximal disease prevention, buyers should seek stock that is reasonably free of disease and should locate their rearing systems properly (see “Location”). The purchaser of breeding stock should always consider requesting a breeder to supply pigs by special procurement procedures, such as MEW or isowean. For example, existing production systems that are positive for the PRRS virus should not introduce PRRSVpositive pigs as replacements (see Chapter 5, “Porcine Reproductive and Respiratory Syndrome”). A breeder can readily produce PRRSV-negative pigs (via isowean) by special order.

Genetics In modern-day pork production, superior genetically improved stock is supplied as prolific females and semen from performance-tested boars. Some breeders create a production pyramid (Figure 6.12) composed of a genetic nucleus, semen collection and processing center (boar stud), a production nucleus, and multiplier farms. Greatgrandparents (GGPs) are produced in the genetic nucleus (GN) herd under intense Table 6.10 Complexity of Disease Exclusion. This Table Includes Most of the Important Infectious Agents That Cause Disease in Swine International/National

African Swine Fever Classical Swine Fever Foot and Mouth Disease Brucellosis Tuberculosis PRV (Aujeszky’s Virus)

Breeding Stock Supplier

Streptococcus suis Type 2 Meningitis Swine Dysentery Ectoparasites Actinobacillus pleuropneumoniae, and Mycoplasmal Pneumonia Atrophic Rhinitis Swine Influenza PRRS Exclusion

Possible

Commercial Producer

Escherichia coli and Rotaviral Diarrhea SMEDI-Parovirus Ileitis PMWS (Circovirus) Mastitis/Metritis/Agalactica Glasser’s Disease Clostridial Infection Salmonellosis Leptospirosis Internal Parasites Difficult

143

Multi-site Pig Production

Figure 6.12 Typical breeding stock production pyramid.

selection pressure. GGPs are then used in the GN, in the boar stud for semen production, and in the production nucleus (PN) herd. The PN produces grandparents (GPs) for distribution to the multiplier herds, which produce parents for sale to the customer. Boars and gilts within the GN herd are performance tested based on proprietary genetic indices. In some companies, molecular-based nucleic-acid-probe-assisted selection (synonym: marker-assisted selection) is used in conjunction with statistically based animal breeding technology. The highest-indexing boars (semen) and gilts are used only within the GN to achieve pigs of higher and higher performance. Unwanted heritable traits associated with classical genetic selection also can be eliminated by probe-assisted selection. The second highest–indexing gilts are supplied to the production nucleus herds for production of both great-grandparents and grandparents to be placed in multiplication herds. Semen is supplied to production nucleus and multiplier farms from the semen collection and processing center. Second highest–indexing boars are usually supplied only to company-owned and commercial boar studs. The third highest–indexing boars are supplied as natural-service boars to customers. Most pork producers purchase only parent gilts and semen from breeders. Commercial slaughter-pig producers with 2000 to 100,000 sows may find an economic advantage in purchasing grandparent females and producing their own replacement parent gilts (which sometimes is referred to as closed-herd multiplication). Commercial pork producers and/or vertically integrated operations of 100,000 sows or greater may be able to arrange the purchase of great-grandparent stock. 144

6. Policy Decisions and Opportunities

Source of Breeding Stock Suppliers of breeding stock should be carefully scrutinized. Veterinarians should determine the health status of the nucleus and multiplier herds of various breeders. Geneticists should evaluate the genetic improvement program of the breeder. Determination of Health Status — The health status of all pig herds can deteriorate over time (see Chapter 3, “Altering the Microbial Flora”). It is relatively easy to monitor and determine the disease level in one-site and traditional two-site farms by clinical observation and inspection of carcasses at slaughter (see Chapter 8, “Determining the Health Status of Pigs Produced in a Multi-site System”). In general, limited microbiologic testing by culture and serologic assays is utilized. Health status is often determined by production performance–record analysis. Maintenance of health status is directly associated with sound biosecurity management practices (see Chapter 7, “Biosecurity”). The same criteria can be used for breeding stock produced in multi-site systems with one exception. If site 1 of a multi-site isowean farm is infected with a pathogen and an attempt is being made to produce pigs free of that particular agent, microbiologic testing is required to assure that post-weaning pigs are free of the agent in question (see Chapter 8, “Laboratory Diagnostic Tests”). Determination of Genetic Potential — Production records of customer farms should be made available for analysis. Litter size by parity should be of particular interest. Pigs from these farms can be sent to specific slaughter plants for carcass analysis. These data can be compared with data supplied or accumulated from other breeders before making a final selection of the breeding stock supplier. Straight-line Distribution — Breeding stock companies often create more than one pyramid of production within each country to minimize the risk of serious disease affecting its entire system. Breeding stock should originate from only one pyramid of production. Boars may originate from a nucleus herd and gilts from a multiplier herd within the same pyramid. New herds should never be stocked from more than one multiplier or from herds in different pyramids. Replacement breeding stock should come from the same herds and the same pyramid as the original stocking unless serious disease occurs in the supply herds. Ideally, a boar stud should supply semen to herds within only one pyramid. Inadequate Numbers of Breeding Stock for Large Herds — In the United States, Canada, Spain, Mexico, Brazil, China, and Thailand, the pork industry is expanding rapidly with the creation of multi-site isowean production systems with more than 20,000 sows. The demand for parent gilts by any one slaughter-pig production company can easily reach 10,000 to 30,000 animals per year. Many owners and senior managers have stocked new herds from a variety of sources and breeding stock companies due to a short supply of gilts in an expanding industry. Sometimes these sources are from several farms and from one or more breeders. Disease 145

Multi-site Pig Production

problems have plagued these start-up situations even when the new herds were set up with multi-site rearing systems. The management practices discussed in Chapter 7 will decrease these problems. However, strategic planning for herd expansion and the placement of orders several months in advance with breeders to minimize multiple sourcing of stock is an important factor for disease prevention during and after start-up in any rearing system. Replacement Breeding Stock — Whenever possible, the same herd used for the original stocking should be the source of replacement stock. If replacements are not available from the original source, veterinarians should scrutinize the health status of a list of candidate herds (within the same pyramid if possible). The health status of the supply herd should match the health status of the recipient herd. Please read the introduction and “Disease Breakdowns” in Chapter 8 for further directives regarding safe procurement and introduction of replacement breeding stock. Special Requests for Breeding Stock of a Defined Health Status — Breeding stock produced in multi-site systems or by the use of isowean technology can more readily meet buyer criteria relating to the absence of specific infectious agents. Such requests depend on forward planning and possibly on associated additional costs.

Location Location of the production system is likely one of the most important and the most difficult considerations for new operations. Traditional producers are often restricted to the property they own or to property adjacent to their various enterprises, whereas some companies are able to locate in any geographic area. However, state and county zoning laws and restrictions, particularly in Europe, Japan, and the United States, can prevent construction in certain locales for all producers. The production of pork has been totally banned in Singapore. The factors to address for the location of new operations are: Geographic terrain and predominant winds. Climatological characteristics. Pig density of the surrounding geographic area. Distance between various sites in a multi-site system. Distance away from other pigs and pig buildings. Distance away from feed production facilities. Distance away from buying stations and slaughter plants. Distance from major and minor roadways (especially those traveled by transport vehicles carrying pigs). 9. Distance away from both metropolitan areas and individual family dwellings. 10. Distance away from streams, rivers, and natural wetlands. 11. Feed and water supply. 1. 2. 3. 4. 5. 6. 7. 8.

146

6. Policy Decisions and Opportunities

12. 13. 14. 15.

Availability and adequacy of land for manure application. Nature of the land with regard to soil type and woodlands. Availability of land for future expansion. Availability of human resources for labor and management.

From the aspect of maintaining pig health, infectious agents that can cause serious disease and financial loss can be carried into a facility on the wind and/or via the water supply. There are reports of some very resistant pathogens traveling up to 20 miles in wind plumes. Wind carriage of pathogens is greater in flatlands without woods and over large bodies of water than in mountainous and hilly regions. High humidity and low temperatures can increase the survivability of some infectious agents. Increasing the distance between each location on which pigs are reared or congregated decreases the likelihood of infectious agents being carried via the wind between sites. The numbers of pigs at each location further complicates the actual distance of separation required. The more pigs on a particular site increases the possibility that more infectious agents will be available to be carried to another location. Low temperatures decrease the effectiveness of disinfectants. Freezing temperatures sometimes prohibit workers from even attempting to clean and disinfect equipment and transport vehicles in unheated buildings or outdoor washing facilities. Shallow wells can be contaminated with infectious agents, nitrates, and/or chemicals for weed control from surface runoff. Open ponds, streams, and rivers should never be used as a source of water unless the water is filtered and treated according to human consumption standards. Infectious agents can be introduced into a farm via the feed. Raw materials such as meat, bone meal, and animal fat may be contaminated. Trucks used to transport both grains at harvest and pigs to slaughter can contaminate corn, milo, wheat, and soybeans. Placing pig farms in well-isolated locations, which is ideal from a disease control viewpoint, can increase operational costs to a prohibitive level due to transport costs associated with feed supply and available markets for slaughter pigs. Thus, it is difficult to set strict parameters for the location of herds with regard to distances away from other pigs or areas of possible pig contamination. It is advisable to seek the services of consultant veterinarians who are knowledgeable in such matters. Odors generated by pig waste in pig-rearing facilities or manure-storage systems can cause human health problems or can affect the quality of human life and the value of residential property. Soil type can be important for manure application and environmental stewardship.

Rearing System The various types of one-site and multi-site production systems have been described in Chapter 2. The separation of the various stages of production in multi-site systems into (1) breeding production stage, (2) nursery production stage, and (3) finisher production stage has facilitated expansion of the pork industry, particularly in the United States, Canada,

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Mexico, Spain, Brazil, and China. Fundamental questions to be answered prior to choosing a rearing system are: 1. What does the strategic plan predict for the total number of sows or of pigs produced? 2. Are breeding stock, slaughter pigs, or both to be produced? 3. Will facilities and/or pigs be wholly owned or contracted? In general, multiple-site and NurFin isowean systems require a larger number of pigs to justify both capital and operating costs. In the United States, there are many financially successful two-site and three-site isowean systems with approximately 2000–2500 sows. Several of these two-site and three-site isowean systems can be combined and converted into multi-site isowean systems. Some pork producers may be more suited to managing one of the stages of production and/or be more able to finance the construction of a stage 2 nursery rather than a stage 3 finisher building. For example, some farmers may be more suited to weaner-pig management than to finishing or breeding, gestation, and farrowing management. The amount of capital and labor required for an isolated nursery for 1 week’s production in a threesite (multi-loci) system might be less than for a finisher site in the same system. Thus, creative financing can be applied at several tiers of the equity base in the community. Also see “Choosing a Multi-site Isowean System.”

Transport of Pigs Figure 6.13 illustrates the transport vehicles used in a production system composed of a multiplier herd producing isowean pigs as replacements for a three-site production system. Some vehicles are used exclusively for moving pigs between the various stages of production. Specific vehicles are assigned for the transport of slaughter pigs. These vehicles do not transport breeding stock or young growing piglets, which is a method of decreasing the chance of infectious-agent introduction. The most common route of horizontal infectious-agent introduction into a pig farm is via transportation systems contaminated with an infectious agent. Transport vehicles should be cleaned and disinfected properly prior to loading pigs from a farm or site of production. In geographic locales that have below-freezing temperatures, washing and disinfecting facilities that are properly enclosed and heated for transport-vehicle cleaning must be constructed. The lack of adequate cleaning facilities for transport vehicles is the most common mistake made by senior managers and owners constructing new swine-rearing systems. Transport-vehicle cleaning and disinfecting facilities should be well isolated from all other livestock enterprises (Figures 6.14 and 6.15). Detailed protocols for the actual transport of pigs also must be written and implemented by management. Owners and senior managers must provide the capital and

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Figure 6.13 Transportation designation of dedicated vehicles by stage of production for a three-site system. Vehicle A only moves isowean pigs. Vehicle B only moves pigs from site 2 loci to site 3 loci. Vehicle C only moves pigs from finishers at site 3 loci to the slaughter plant. (Modified from illustration by Claudio Freixes)

Figure 6.14 Transportation-vehicle cleaning and disinfecting facility.

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Figure 6.15 Transportation-vehicle cleaning and disinfecting facility.

leadership to ensure that the farmworkers can accomplish protocols. Procedural matters of most importance are: 1. Transport-vehicle personnel movement and location during loading and unloading of the pigs. 2. Farm personnel movement and location during loading of the pigs. 3. Cleaning, disinfecting, and dry-down methodologies. 4. Assignment of transport vehicles for only specific types of uses. 5. Wholly owned transport vehicles versus the use of hired haulage. 6. Monitoring the level of sanitation of transport vehicles after they have been cleaned and disinfected. 7. Removal and transport of cull animals. 8. Removal and transport of dead animals. 9. Feed delivery. 10. Service-personnel transport vehicles. 11. Waste-handling transport vehicles. 12. Slaughter-pig loading and transport. 13. Outgoing breeding-stock loading and transport. 14. Incoming replacement breeding-stock transport and unloading. 15. Location of facilities for cleaning and disinfecting transport vehicles. 16. Procedural aspects of transporting pigs from one site to another. 17. Welfare of the pigs during loading and unloading as well as flooring, bedding, length of time of travel, and care during the traveling period.

Building Design and Materials It is beyond the scope of this book to address all of the construction and engineering issues related to building design. However, several matters regarding disease control, pig performance, and welfare are worthy of note. 150

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Figure 6.16 Biosecure load-out design. (Design by Steve Thomas, PIC, 1989)

Load-in/Load-out Facilities — Load-in and load-out rooms and chutes should be constructed adjacent and connected to various buildings in the system (Figures 6.16 and 6.17). Special consideration should be given to: 1. Providing a means to properly clean and disinfect load-in/load-out facilities after each use. 2. Providing heat to prevent freezing so the facilities can be disinfected properly. 3. Installing one-way gating so that pigs cannot regain access to the unit once they are in the load-out area. 4. Having a large enough holding capacity to completely fill a transport vehicle without repeatedly bringing in more pigs from the unit during the load-out process. Important features of the biosecure load-out design in Figure 6.16 are a door or gate to prevent re-entry of pigs back into the farm; construction that allows complete cleaning and disinfection; a separate waste-disposal system from the farm; pen floors sloped to the dirty side; totally enclosed and/or bird-proofed building and all walkways; and the whole load-out at the level of the transport trailer or equipped with a ramp with no more than 20% slope. Isolation and Acclimatization Facilities — It is extremely important that adequate isolation and acclimatization facilities are constructed for the introduction of replacement breeding stock. Replacement breeding stock should be isolated 3–4 weeks prior to being acclimatized to the microbial flora of the recipient farm. During this isolation period, the replacements should be held in strict isolation away from all other pigs to determine if they are infected with any economically important diseases (see Chapter 8, “Determination of the Health Status of Pigs Produced in a Multi-site System”). The supply herd of the breeder could become diseased during this 3–4 week period if the herd was in the incubatory stages of disease at the time of shipment. If the supply herd reports a disease problem, the newly purchased animals could be slaughtered rather than being placed in the recipient farm. After the isolation period, the pigs should be acclimated at least 30 days prior to being bred. For introduction of PRRS-infected animals, acclimation can take over 60 days and must take place in isolation as well (see Chapter 5, “Porcine Reproductive and Respiratory Syndrome”). 151

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A. B.

▲

Figure 6.17 Load-in/load-out ramp for a site 2 nursery production stage locus. A. Outside view. B. Inside view. The load-in ( ) is at the lowest level to facilitate off-loading of isowean pigs from a trailer. The load-out (arrow) is at a higher level to facilitate a larger transport vehicle when the pigs are to be moved to a site 3 finisher production stage locus.

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Figure 6.18 Isolation facility for incoming replacement stock. The isolation unit (arrow) is located a safe distance away from the breeding production stage.

Ideally, the isolation facility should be located 1–2 miles away from the recipient herd (Figure 6.18). If this is not possible, any degree of isolation in a separate building is better than none. All-in/All-out Pens, Rooms, Buildings, or Loci — The following aspects of all-in/all-out production should be addressed: 1. Ventilation system. 2. Materials used for flooring, walls, ceilings, feeders, and waterers so pens can be properly cleaned and disinfected between groups of pigs. 3. Waste-handling design. The greatest economic benefit in productivity is gained by all-in/all-out pig flow by locus in stages 2 and 3 (Figure 6.19). Decreasing benefit occurs sequentially with allin/all-out by building, room, and pen, respectively. All-in/all-out rooms within a building, such as farrowing or nursery rooms, should be designed so that the inlet air does not come from an adjoining room. Solid walls should separate these rooms. Conversely, outlet air should not enter any rooms associated with the building. Sewage outlet pipes should be designed so that it is impossible for a plugged line to cause backup of manure into any other room in the building. Ideally, when more than one building is on a locus, each building should house only one age group of nursery or finisher pigs. If not, strict adherence to all-in/all-out by room pig flow should occur.

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Figure 6.19 Production performance estimates of five all-in/all-out pig flows and a continuous flow throughput. (Modified from Gadd, 1997; Evans, 1997)

Feeding Program — In the United States, 55% to 65% of the total cost of production for a slaughter pig is feed. Proper feed intake is achieved by maintaining high–health status, split-sex grouping, and multi-phase diets. High–health status pigs require more lysine but have greater lean/gain ratios and more lean carcasses. Steve Dritz and Mike Tokach at Kansas State University estimates that overfeeding lysine by 0.1% results in an increased feed cost of $1.20 per pig. By contrast, underfeeding lysine and lowering the lean percentage in a carcass by 0.5% leads to a reduction in net income of $0.60 per pig and increases feed cost as a result of poor feed efficiency. Male pigs grow at a different rate than female pigs. At least four different diets are required for growing pigs to maximize feed intake and rate of gain. Buildings housing pigs all-in/all-out by room must have separate feed-storage delivery systems to facilitate the particular diet required by a specific age group by room. Feed intake is necessary for maximal growth. The following factors influence feed intake: 1. Genotype. Some breeds, such as Duroc, have higher rates of feed intake. 2. Sex. Barrows eat more feed per day than do gilts. In some studies, this effect has been shown to begin at weaning. 3. Body weight. The larger the pig, the greater the feed intake. Greater feed intake does not equate directly to gain as slaughter weight is approached. Growth curve analysis is recommended to calculate proper diets for phase feeding to reduce cost and maximize gain. 154

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4. Temperature. Feed intake decreases as the temperature increases. 5. Feeder type. Feeder type and liquid versus dry feed influence intake. Liquid feeding increases feed intake by 10%–15%. 6. Floor space. Total floor space and group size influence feed intake. Experimental data in which floor space is not limited and pigs are fed individually may be very misleading. Large groups of pigs that are overcrowded have very depressed feed intake. 7. Dietary factors. Nutrient content, ingredient levels, and quality of ingredients can influence feed intake. Diets deficient in amino acids will depress appetite. 8. Water. Inadequate water supply and water of poor quality can depress feed intake. Pig Welfare — It is common for newly constructed buildings to cause abrasions to the skin and damage to the joints of pigs, especially in buildings without bedding. Senior management and owners must consider this to be unacceptable and take special precautions to prevent it. Designs and materials that have not been previously utilized for rearing pigs should be avoided. Sanitation — Pig-rearing facilities should be constructed of materials that are easy to clean and disinfect. All-in/all-out rearing strategies call for cleaning and disinfecting between groups. Proper equipment and hot water should be provided to facilitate sanitation procedures. It is common to attempt eradication of pathogens in multi-site isowean systems; therefore, consideration should be given to constructing buildings that are easy to clean and disinfect.

Food Safety and Pork Quality Purchasing pigs of high–health status, maintaining strict biosecurity policies, and avoiding the introduction of diseased replacement stock is the best way to minimize the contamination of the pork chain by feed additives and injectable drugs, physical contaminants such as injection needles, and human infectious microbes originating from farms. Senior management and owners should implement a Hazard Analysis Critical Control Point (HACCP) program as part of the quality-control effort of their pig production operation. The National Pork Producers Council (NPPC) in Des Moines, Iowa, can be contacted for further information on HACCP and the NPPC Pork Quality Assurance programs. The design of load-outs and the transportation vehicles used for slaughter pigs can have a big impact on meat quality. Alleviation of stress on the pig during loading and transport should be a priority of owners and senior managers.

Summary There is a financial advantage to producing pigs via multi-site production systems. However, multi-site isowean production is not for everyone; it requires a greater level of sophistication regarding building design, biosecurity, and overall management. A combination of both production and financial targets are used to monitor multi-site production systems by using the DuPont Equation to understand substandard performance. 155

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The variety of multi-site systems gives a range of possibilities for all sizes of pork producers to utilize. Probably the greatest advantage to multi-site systems is the capability to expand operations rapidly in an environmentally friendly capacity. This allows any pork producer to maintain competitiveness by increasing output at less cost and to manage leverage to maximize the value of assets. To maximize the advantage of multi-site production systems, owners and senior managers must provide managers and pig-care workers with the proper buildings, transport vehicles, location, and pigs.

Bibliography Alexander, T. J. L. 1987. Disease control for optimum productivity. Presentation at a seminar in Tokyo, Japan. Alexander, T. J. L. 1998. Personal communication. Barcelo, J. and E. Marco. 1998. On-farm biosecurity. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 129–133. Bonneau, M. 1998. The cost of building and maintaining an isolation unit. Allen D. Leman Swine Conference. Vol. 25. 1998, 103–106. Veterinary Outreach Programs, University of Minnesota, St. Paul. Brummer, F. 1998. The quest for the perfect wean-to-finish building. Allen D. Leman Swine Conference. Vol. 25. 1998, 223–227. Veterinary Outreach Programs, University of Minnesota, St. Paul. Castro, G. 1998. Personal communication. Connor, J., P. Bahnson, and B. Christianson. 1994. Economic justification of isolation/segregation of incoming breeding stock. Proceedings of the 13th International Pig Veterinary Society Congress, Bangkok, Thailand, 437. Connor, J. F. 1998. Personal communication. Connor, J. F. 1998. Wean-to-finish construction alternatives, management, and performance. Allen D. Leman Swine Conference. Vol. 25. 1998, 219–222. Veterinary Outreach Programs, University of Minnesota, St. Paul. Cumberland, T. 1998. Personal communication. DiPietre, D., L. Fuchs, and R. Tubbs. 1997. Using the DuPont model. Allen D. Leman Swine Conference. Vol. 24. 1997, 95–102. Veterinary Outreach Programs, University of Minnesota, St. Paul. Drabenstott, M. 1998. This little piggy went to market. Will the new pork industry call the heartland home? Allen D. Leman Swine Conference. Vol. 25. 1998, 30–41. Veterinary Outreach Programs, University of Minnesota, St. Paul. Dritz, S. S. and M. D. Tokach. 1998. Growth curve analysis to determine profit optimization and pig flow. Allen D. Leman Swine Conference. Vol. 25. 1998, 136–141. Veterinary Outreach Programs, University of Minnesota, St. Paul. Drum, S. D. and W. E. Marsh. 1999. How to use partial budgets to predict the impact of implementing segregated early weaning in a swine herd. Swine Health and Production 7:13–18. Drum, S. D., R. D. Walker, W. E. Marsh, M. M. Mellencamp, and V. L. King. 1998. Growth performance of segregated early-weaned versus conventionally weaned pigs through finishing. Swine Health and Production 6(5):203–210.

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Dufresne, L. 1995. Observations and results in different segregated early weaning and multiplesite production systems. Allen D. Leman Swine Conference. Vol. 22. 1995, 170–173. Veterinary Outreach Programs, University of Minnesota, St. Paul. Evans, M. 1997. Personal communication. Freixes, C. 1999. Personal communication. Gadd, J. 1997. The segregation aspects of segregated early weaning. Animal Talk 4 (No. 9), Nottingham Nutrition International newsletter, United Kingdom. Gausman, G. 1998. Personal communication. Hurt, C. 1995. Summary and conclusions. In Positioning Your Pork Operation for the 21st Century. Purdue University Cooperative Extension Service Publication. Jolly, R. W. 1995. Financial Troubleshooting. Iowa State University Extension Publication, 1–8. Jolly, R. W. 1998. Personal communication. Lawrence, J. D. 1996. Economic evaluation of new technologies for pork producers: Examples of all-in/all-out and segregated early weaning. Swine Health and Production 4(4):175–180. Moore, C. 1995. Using high-health technology in a modern production system. Allen D. Leman Swine Conference. Vol. 22. 1995, 18–25. Veterinary Outreach Programs, University of Minnesota, St. Paul. Ollivier, L. 1998. Genetic improvement of the pig. In The Genetics of the Pig, ed. M. F. Rothschild and A. Ruvinsky, 511–540. CAB International, New York.

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The manager is charged with the overall production performance or efficiency of a multisite system. According to Robert Jolly at Iowa State University, owners or owner/managers of farms must consider three factors to judge financial performance of a farming operation: efficiency, scale of operation, and debt structure. Efficiency is a direct reflection of the managerial skills of both the manager and the owner. Poor efficiency cannot be the sole cause of poor financial performance, but excellent production performance is essential to acceptable profitability and liquidity. The manager of a multi-site system must have a disciplined approach to pig production. Multi-site systems provide the opportunity to develop a staff with each member having very specialized skills. The manager is responsible for the overall training of personnel and the development of a staff of highly motivated individuals who work as a team with the welfare of the pigs in mind at all times. Production performance measures were listed in Table 6.3. The scale of operation and debt structure, which are concerns of owners only, were addressed in Chapter 6. Gordon Spronk of Pipestone, Minnesota, considers the following as the key technical aspects of multi-site production systems: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Site 1 sow herds located in well-isolated areas of low pig density. Stabilization of sow herds by vaccination and acclimatization. Average wean age of 16–18 days. Large groups of isowean pigs with less than a 7-day age spread available. Isowean pigs moved on a group basis to nursery as single source. Group identification assigned at weaning and maintained until slaughter. Pigs moved to finishers as a single source and kept separate from other pigs and age groups. Fill time of nursery and finishers of less than 1 day. All-in/all-out by locus preferred; by building if necessary. All facilities washed and disinfected between groups. Pigs moved from nursery to finisher by pen; maintain pen integrity. Transport system standardized and managed centrally. Health status monitored by sow site and by weaned-pig group. 158

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Table 7.1 Range and Values of Production Parameters for the Top 10% of Pigs in the Pipestone Swine System Range

Top 10%

Age into nursery (day) Days in nursery ADG (lb) FC % Mortality Weight in (lb) Weight out (lb)

14 to 18 42 to 60 .65 to 1.10 1.4 to 1.85 0 to 7% 7 to 12 40 to 60

14 to 18 50 1.15 1.35 0.50% 11 65

Age into the finisher (day) Days in finisher ADG (lb) FC % Mortality Weight in (lb) Weight out (lb) Total days to market (birth to market)

56 to 78 100 to 125 1.45 to 2.0 2.55 to 3.4 0.17% to 8% 40 to 60 235 to 295 156 to 203

60 110 1.88 2.75 1.25% 65 255 170

Wean-to-finish data (all groups) ADG (lb) FC % Mortality Days in finisher

1.51 2.45 3.0% to 5.09% 160

Source: Modified from Spronk et al., 1997.

The Pipestone multi-site system is based upon joint ownership of site 1 sow farms by traditional farmers. Each owner is supplied with isowean pigs that are placed in either nursery or NurFin accommodations. Table 7.1 lists the production performance results of isowean pigs generated in the Pipestone multi-site system. Spronk believes the personnel in charge of the pigs are the most important variable that controls the performance success or failure of a group of isowean pigs. He lists the following as attributes of managers and owner/managers that have consistent high-performing successive groups of isowean pigs: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

Pride of ownership. Follow rules of all-in/all-out by room, building, locus or site. Strict cleanup and disinfection between groups. No pig movement between groups or age groups. Personnel with good husbandry skills. Early recognition of unhealthy pigs. Early treatment of unhealthy pigs. All cull pigs removed from farm. Records kept on each group through each growth phase. Records analyzed to improve performance in next group. 159

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11. Quality of transport between sites. 12. Site and building biosecurity. 13. All loci within sites well separated over a large geographical area. The content of this chapter deals with important managerial considerations for a multisite production system.

Production Targets Achieving the production targets established by the owners or senior managers is the primary goal of any multi-site farm system manager. The performance of the manager is judged based on meeting or exceeding reasonable targets that directly relate to profit or loss. The following targets are achievable: Annual total pig output: 23 pigs times sow inventory Litters/sow/year: Greater than 2.3 Pigs weaned/sow/year: 24–25 Farrowing rate: Greater than 85% Days to market: Less than 190 days Nonproductive sow days: 30 days Feed efficiency: Whole herd, less than 3.2; nursery, 1.5; finisher, less than 3.0 Mortality: Sow herd, less than 4%; pre-weaning, less than 8%; nursery, less than 2%; finisher, less than 1%; NurFin, less than 2% 9. Vaccines, drugs, and feed additives: Less than $3.00/slaughter pig sold

1. 2. 3. 4. 5. 6. 7. 8.

The manager is responsible for keeping very accurate production records. If any of the above targets are not being met, the manager should analyze the production record data to ascertain the reason and take appropriate action to meet the target. Several factors can interact with the management of a farm and have an impact on achieving production targets. Important interactive factors that were addressed in Chapter 6 are the health statuses of the herd and of replacement breeding stock; genetics of the breeding stock; facilities and buildings; and nutritional program. These factors are not directly related to managerial control. The following interactive factors under direct managerial control influence whether production targets are achieved: gilt development; throughput; feeding; and biosecurity measures.

Gilt Development Gilt development refers to the process of isolating and acclimatizing gilts before they are bred. Gilt development allows the gilts to be prepared for breeding by (1) being exposed to and recovering from infectious agents; (2) receiving vaccinations and producing antibodies to various infectious agents; and (3) becoming sexually mature to maximize the lit-

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ter size in all parities. Properly conducted gilt development aids in the management of the gilt pool and the breeding program, which is essential for proper throughput of isowean pigs. Replacement gilts must be of equal or higher health status than the adult population in site 1 (breeding production stage). Therefore, all replacement gilts must be housed in isolation away from all other swine prior to acclimatization and introduction into site 1. In isolation, the health status of the gilts should be determined by a veterinarian (see Chapter 8 for details). Prior to removal from isolation, the veterinarian in charge of the source farm also should be contacted to ascertain if disease that could impact the health status of the recipient herd has occurred. Following 21 days of isolation, the gilts should be acclimatized by exposure to the microbial flora of the recipient farm. The type of microbial exposure and length of acclimatization depends upon the disease status of the replacement gilts and of the swine in the recipient farm. Because gilts produced in a multi-site isowean system will likely be of a higher health status than their dams in site 1, isolation and acclimatization also are necessary if replacements are generated from within a multi-site system.

Age of Gilt Replacements Traditionally, replacement gilts enter the breeding area when they are at or near sexual maturity. However, gilt replacements can be introduced into site 1 as isowean pigs at weaning or at any age post-weaning. (If selected from a nursery, the pigs are referred to as breederweaners.) The introduction of isowean or breeder-weaner pigs allows more time for acclimatization and can decrease the possibility of reproductive problems due to infectious agents.

Disease Status of the Replacement Gilts Ideally, replacement gilts should be supplied from the same farm that originally stocked the recipient farm and should only originate from one source farm. Changing the source farm and receiving pigs from more than one source increases the chance of introducing new infectious agents into the recipient farm. Prior to receiving the replacements, the veterinarian of the source farm should be contacted to determine the current health status. Once the pigs have arrived and have been placed in isolation (see Chapter 6, “Basic Essentials,” and Chapter 8, “Laboratory Diagnostic Tests”), testing should begin immediately to determine if the disease status is similar to the status of the recipient herd. Acclimatization steps should not occur in isolation until the disease status has been determined. A period of at least 21 days is usually required for isolation. PRRSV-negative Source Farm — If possible, only porcine reproductive respiratory syndrome virus (PRRSV)–negative gilts should be utilized as replacements, even if the recipient herd is infected with PRRSV. A PRRSV-negative mature gilt is defined as a gilt that has not been vaccinated with PRRSV vaccine and whose serum is negative for antibodies as determined by the IDEXX ELISA for PRRS. An isowean or breeder-weaner gilt can test positive (if derived by isowean from a PRRSV-positive sow farm) in the IDEXX PRRS

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ELISA due to maternal antibodies (see Figures 5.1 and 5.2). If positive, a polymerase chain reaction (PCR) test could be considered to determine if PRRSV is present in the gilt. Based on her experience in Denmark, Annette Botner recommends that avirulent live PRRSV vaccines not be given to swine in a PRRSV-negative farm. PRRSV-positive Source Farm — Gilts from PRRSV-positive source farms should never be placed in a PRRSV-negative recipient herd.

Disease Status of Recipient Sow Herd It is important to know the disease status of the recipient herd. A veterinarian can determine this by analysis of production performance records, selective laboratory tests, clinical observation, and slaughter inspection of carcasses. An attempt should always be made to not introduce new infectious agents into the recipient farm. PRRSV-negative Recipient Herd — Replacement gilts that are free of PRRS virus can be readily introduced at or near sexual maturity into PRRSV-negative site 1 loci if they have been isolated for 21 days followed by 21 days of acclimatization. During acclimatization, the gilts should be exposed to cull sows, feces, urine, and saliva from the breeding area of the site 1 locus. When the replacement gilts and the recipient farm are both free of PRRSV, the acclimatization process can take place in site 1 facilities of the recipient farm. PRRSV-positive Recipient Herd — If the recipient sow herd is infected with PRRS virus but the source farm is negative for the PRRSV, the acclimatization period can need to be 60–90 days prior to breeding to allow time for exposure to and recovery from the PRRSV present in the recipient farm. During acclimatization, the gilts should be exposed to cull sows, feces, urine and, saliva from the breeding area of the site 1 farm. In this situation, the acclimatization process must take place in isolation away from the breeding production stage of the recipient farm. Breeding must not occur during acclimatization until all replacement gilts have been infected with PRRSV and have recovered from the infection (see Chapter 5, “Porcine Reproductive and Respiratory Syndrome”). In many instances, however, only PRRSV-positive replacement gilts are available. In this situation, live avirulent PRRSV vaccines can be administered to the gilts either prior to delivery or during acclimatization. Minimal problems with the PRRSV can be anticipated if only one source farm was used for the initial stocking and it continues to be the supply herd, and if no new strains of PRRSV are introduced into the source farm or the recipient farm (see Chapter 8, “Production Pyramids”). An avirulent live PRRSV vaccine administered during acclimatization can be beneficial in preventing disease from PRRSV infection. However, since PRRSV is an RNA-type virus that readily mutates, PRRSV vaccines are not always effective in preventing mutant strains (see Chapter 5, “Porcine Reproductive and Respiratory Syndrome”).

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Isolation Procedures Incoming replacement gilts should be placed in an isolation building well away (preferably 1 mile or more) from all loci in sites 1, 2, and 3. Ideally, the building should be equipped with a shower-in/shower-out area (see “Biosecurity” below). While in isolation, samples can be collected from the gilts and tested for various infectious agents. Simultaneously, pigs of similar age from the recipient farm can be sampled and tested for the same infectious agents. Statistical analysis of the test data will determine if any infectious agents different from those in the recipient herd are present in the replacement gilts. The gilts should be held in isolation a minimum of 21 days to allow time for sampling and diagnostic tests. Also, if the gilts are in the incubatory stages of a disease outbreak, this length of time can allow clinical signs of the disease to occur in the gilts themselves or in the source farm.

Acclimatization Procedures The purpose of acclimatization is (1) to expose the newly arrived gilts to unknown infectious agents present in the recipient herd; (2) to immunize the gilts against known infectious agents, such as PRRSV, parvovirus, and Leptospira organisms; and (3) to allow time for the gilts to build immunity to these agents prior to being bred. A common procedure for exposing the gilts to the unknown agents (and parvovirus and PRRSV) is to place a water suspension of the following materials on their food three times per week for approximately 2 weeks in succession: feces, urine, and saliva collected from the gilt breeding area. If sick PRRSV-infected newborn pigs are available, lungs from these pigs are also placed in the feedback suspension. If PRRSV-negative or PRRSV-positive gilts are being introduced into a PRRSVpositive or a PRRSV-negative herd, the acclimatization procedure must be done in isolation away from the breeding production stage. For this reason, separate isolation and acclimatization facilities are needed for a minimum of 60 days (21 days isolation and 35 days acclimatization) after receiving the replacements and prior to their introduction into the herd. In some cases, if PRRSV exposure during acclimatization doesn’t result in the infection of the replacements, the combined isolation and acclimatization can need to be extended to 120 days (21 days isolation and 100 days acclimatization). Scott Dee has published extensively on the different methods for introduction of both PRRSV-positive and PRRSV-negative gilts. The reader is urged to review his co-authored publications listed in the Bibliography.

NurFin Isolation and Acclimatization Buildings Joe Connor originated the concept of using NurFin buildings to isolate and acclimatize PRRSV-positive replacement gilts. Both isowean and breeder-weaner gilts are placed in a well-isolated NurFin building (see Figure 4.10). Initially, the gilts are tested for infectious agents in a normal isolation procedure. After 21 days, acclimatization with materials from the recipient farm can begin. Once natural exposure to and recovery from PRRS virus has

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been accomplished, these gilts can be considered part of the gilt pool and can even be bred in the NurFin prior to their entry into the recipient farm (see Chapter 5, “Porcine Reproductive and Respiratory Syndrome”).

Throughput Throughput is the volume of production appropriate for the fixed assets in place on the farm. A reasonable level of sow herd inventory must be agreed upon between the manager and the owner or the senior management team. Total annual pig output expectations can then be matched to various building capacities. If necessary, plans should be made for selling off excess production as isoweans or feeder pigs or for establishing contractual arrangements. There is an understandable and natural fear by owners and/or senior managers and farm managers that space will be underutilized. This quite often leads to overproduction and placement of too many isowean pigs per space. Overfilling nursery and finisher buildings results in growth retardation from overcrowding, which is unacceptable inhumane rearing of pigs. This situation must be avoided to achieve maximal growth rates, feed efficiency, carcass quality, and husbandry practices. In a multi-site system, throughput is based on all-in/all-out pig flow by room, building, or locus. Inherent in the system is a lack of flexibility and a requirement for strict managerial discipline. To achieve consistent and achievable pig throughput, the discipline must start in the breeding and gestation areas of the farm.

Breeding and Gestation It is recommended that matings be 100% artificial insemination (AI). The use of AI eliminates the variability of natural service and also decreases the chance of infectiousagent introduction to the farm. Semen must be supplied from an off-site boar stud or purchased from a commercial source. Internal boar studs (boar housing and semen collection within the breeding and gestation area) are not recommended due to the possibility of disease spread from the female population to the boars in the stud and back again via semen. The number of females to inseminate each week depends upon the number of pigs to be placed in the nursery accommodation on a weekly basis. Information derived from pigs weaned per sow per year (pigs born alive per sow, pigs weaned per sow per week, mortality rate in lactation, expected farrowing rate) can be used to make this calculation. To achieve a consistent number of sows farrowing per week, the following three aspects are keys to success: (1) The weekly introduction of gilts to the sow farm from the gilt development area, both pregnant and open; (2) a breed-to-abort program; and (3) the prediction of seasonal farrowing rate variation. Three types of gilts introduced each week into the sow farm from the gilt developer are (1) bred (the majority of the gilts should be bred); (2) in detected heat but not bred (DH); and (3) in undetected heat (UH). Bred gilts are placed to match the weekly group of weaned sows. If the number of bred gilts exceeds the targeted number of pregnant

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females for a group, some gilts should be aborted to meet the target for that particular weekly group and bred back 4–6 days later. To abort, inject the sow with prostiglandins 15–45 days post-service. Prostiglandins can be given beginning 2 weeks after fertilization and the gilts will be in estrus in 5–7 days. The DH gilts are moved into the farm 4–10 days prior to their next heat cycle. The UH gilts are utilized as heat is detected or they are culled. In the midwestern United States, weekly mating targets are the same for the months of November through January. From June through October, mating targets are increased each month to account for seasonal depression in the farrowing rate.

Farrowing Ideally, personnel are present 24 hours a day. In very large systems, two teams can be in place: A perinatal team for the first 10 days post-farrowing and a lactation team from day 11 until weaning. A targeted weaning age must be predetermined. Utilization of the Isowean Principle allows a weaning age of less than 21 days. This has been driven by the improved health status of isowean pigs and an increase in female productivity. A range in weaning age of 14–17 days can be optimal for most herds. The brain, the uterus, and the ovaries need time to recovery from parturition. All three organs are usually recovered by 14–15 days after farrowing. Many infectious agents can be eliminated by a 14- to 17-day weaning age (see Chapter 3, “Elimination of Infectious Agents by MEW and Isowean”). Some infectious agents can require earlier weaning. In this case, PG600 (a combination of equine chorionic gonadotropin and humna choionic gonadotropin) can be injected at weaning to reduce the weaning-to-estrus interval. Sows that do not farrow with the others in the room can be moved to a room with nonfarrowed sows. It is better to cross-foster pigs within a room and within 36 hours of age. All farrowing rooms should be managed on an all-in/all-out basis with a weaning age spread of less than 7 days per room. For the first 5 days after farrowing, sows should be fed two times day. Beginning on day 6 post-farrowing, sows should be fed ad libitum in 3-pound amounts. Sows should be full-fed as frequently as is required.

Nursery Upon arrival, pigs should be separated into uniform groups according to sex and size. Usually pens are sized to accommodate approximately 20 pigs at 3.0 square feet per pig. Rooms, buildings, or sites should be filled within a 24-hour period. Most systems allow for pigs to remain in the nursery for 7 weeks, with complete emptying, cleanup, and disinfection of the nursery in the 8th week. Great care and attention must be given to the piglets immediately post-weaning. Most managers provide comfort mats for the pigs the first few days and hand-feed the piglets on the mats. The room temperature or localized heating should provide an 85° F floor temperature for the piglets.

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Finisher Pigs should be transported to the finisher so that pen integrity is maintained. If this is not possible, room integrity (pigs housed in the same airspace in the nursery) should be maintained. Finisher buildings or loci are turned every 17 weeks. This allows 16 weeks of growth and 1 week for cleanup and disinfection. Nursery and finisher buildings should not be overstocked with pigs. Approximately 7 square feet per pig is recommended. Excess pigs must be sold or placed elsewhere to allow adequate space for optimal growth. If optimal growth is inhibited, weight-for-age can be reduced dramatically.

NurFin (Wean-to-Finish) Building The main advantages of NurFin buildings are decreased labor demands for the transport of pigs and for the cleanup and disinfection between groups. The main disadvantage is the suboptimal use of space in the first few weeks after weaning (see Figure 2.18A). Improved space utilization can be achieved by double filling at weaning; however, an additional transport cost is then incurred unless the finisher is located on site. A NurFin building requires the manager to pay greater attention to proper supplemental heating and appropriately sized and located waterers.

Feeding In the United States, feed accounts for 60% of the cost of production. In Europe and China, feed can reach 80% of operating costs. Management must put in place strict controls to minimize feed wastage. Disappearance of feed is the best way to judge feed consumption and wastage. All-in/all-out pig flow allows for very accurate data collection. All pigs must be weighed when entering and leaving a room or building. Each room or building must have a separate feed bin. Feeders must be checked daily for feed wastage, and appropriate adjustments must be made. When rooms or buildings are emptied, the bins must be emptied and the feed weighed, or some other accurate method of estimating the feed remaining must be developed. To achieve maximal growth performance, an isowean pig must receive a variety of diets during the growing period (multi-phase feeding). By maintaining consistent throughput without overstocking, the exact amount of each diet needed per growth phase can be calculated based on the weight and number of pigs placed in a room, building, or locus. In this way, the manager can control the amount of each diet delivered for feeding. This is particularly important for expensive rations required for feeding young isowean pigs.

Biosecurity Biosecurity is defined as the rules and procedures implemented to prevent infectious agents from entering each stage or site or building of production. Biosecurity for a multi-site system involves prevention of infectious-agent contamination by (1) hori166

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zontal introduction from outside the multi-site system; (2) intra-site horizontal transfer from one locus to another within a site; and (3) inter-site vertical transfer between sites of production. Strict managerial control of the movement of pigs, personnel, and vehicles is the key to successful biosecurity and prevention of infectious-agent introduction or spread. The manager must strive to maintain the existing health status of the pigs in the operation rather than allow new infectious agents to be introduced. Successful maintenance of health status will help assure the benefits in growth rate, feed efficiency, and carcass quality achievable via the Isowean Principle. Multi-site systems are also designed to elevate health status via the Isowean Principle. A major advantage of multi-site systems over one-site and traditional two-site farms is that an improved health status can be readily achieved without total depopulation. But when using the Isowean Principle to elevate health status, measures must be taken to prevent inter-site transfer of infectious agents vertically from site 1 to sites 2 and 3 and from site 3 back to sites 1 and 2.

Airborne or Aerosol Transmission of Infectious Agents Infectious agents can be spread or be transferred between sites, loci, buildings, or rooms by the airborne route. In fact, under ideal environmental conditions, infectious agents can travel several miles. However, from a practical standpoint, transfer of infectious agents via aerosol between sites and loci that are one-half to several miles apart is not common. Aerosol transfer within and between rooms is very common, and there is always a possibility of aerosol transfer between buildings that are 50–100 feet apart within a locus. Figure 7.1 illustrates the actual distances that some infectious agents of swine have been shown to travel. There is usually very little the manager can do to prevent aerosol transfer of infectious agents since this mode of transmission primarily depends upon location and the design of the facilities (see Chapter 6, “Basic Essentials”).

Procedural Aspects of Unloading and Loading Pigs Unloading from and loading pigs onto transport vehicles are some of the most likely modes of introducing disease into a pig farm. If properly cleaned and disinfected transport vehicles (including the cab and the stock rack) are utilized, it is unlikely that disease will be introduced. Unfortunately, the manager and the personnel within the pig farm in some situations may have no control over the cleanliness and management of the transport vehicles going and coming from a farm. Management can address this issue in several ways, as outlined in the following paragraphs. The key to prevention of disease introduction via this route is simply not to allow people, pigs, or materials present on a transport vehicle to enter the pig-rearing facility. Furthermore, if a breach in this policy occurs, a clear set of action steps must be taken immediately to assure thorough cleaning and sanitation at the point of entry of the contaminant. Load-in/Load-out Facilities — Figure 6.16 is a diagram of an ideal load-in/load-out facility. In that design, it is assumed that contaminated transport vehicles can be utilized 167

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Figure 7.1 Distance microbes (both nonpathogens and pathogens) traveled from a swine-rearing facility in a downwind plume. (Heber, 1996. Reprinted with permission from the National Hog Farmer)

to load-out pigs from the facility. Ideally, such a facility is located 50–100 feet from the main complex. In this way, workers from the farm can move the pigs into the facility prior to the arrival of the transport vehicle. The driver then loads the pigs without entering the “clean side” aisle. If more pigs are needed to fill the truck, the farmworker can move additional animals into the facility through the nonreturn door. After the loading is completed, a person can clean and disinfect the facility. If this person is to re-enter the pigfarm compound, the person should go through a clothes-changing procedure (including a shower/bath if possible). In regions of possible below-freezing temperatures, these facilities need to be totally enclosed and heated to allow thorough cleaning and disinfection 168

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between loads. Disadvantages of this approach are the cost of the load-in/load-out facility; its separate location away from a main building (which increases the distance to move pigs prior to placement onto the transport vehicle); and the necessity of having such a facility at every major building or locus of the production system. A much simpler load-in/load-out structure consists of a small holding area and a loading chute incorporated within a building. In these designs, the nonreturn door is usually placed at the base entry point of the loading chute. The farmworker usually moves the pigs through the nonreturn door and the driver moves the pigs up the chute without entering the production unit. The major disadvantage of such an approach is the possibility of contaminated drainage accumulating in the bottom of the chute area and then migrating into the production facility. A properly placed drain at the base of the chute can minimize the likelihood of contamination. Inner-sanctum Transportation System — David Hollier, former general manager of PIC, originated the concept of inner-sanctum pig transport to avoid contamination of production sites, loci, and buildings within multi-site systems. Ideally, this approach involves two sets of transport vehicles and two cleaning and disinfection facilities (truck washes). The inner-sanctum trucks and truck wash are only used for the transportation of pigs between sites and loci or within a locus. The outer-sanctum trucks and truck wash are only used for removal of pigs destined for slaughter or for sale as breeding stock. Any truck in the outer sanctum that has made an off-site (any contact point of delivery not associated with the multi-site system) delivery must be thoroughly cleaned and disinfected prior to being used again to haul pigs from the production facility. Shuttle Transport — In some situations, two transport vehicles can be used to either receive or discharge pigs from a building. This is very useful when several smaller batches of pigs from more than one building are to be loaded (shuttled) onto one large transport vehicle. In this case, the shuttle vehicle must be thoroughly cleaned and disinfected between each shuttle. All-in/All-out Finisher Building Closeouts — Care should be taken to not contaminate the finisher building or locus with vehicles returning from slaughterhouses. The transfer of infectious agents from slaughterhouses to finisher buildings and loci should be avoided even during closeouts. It is possible that both pig disease agents and/or human foodborne infectious agents could be introduced into pigs during the final stages of the finishing phase. Furthermore, poor management of this situation could result in transfer of infectious agents throughout the entire multi-site system.

Possible Transfer of Infectious Agents on or within Personnel Infectious agents can be carried into pig-rearing facilities on the boots, clothing, skin, and hair of personnel. Ideally, all “street” clothes and footwear should be removed and a shower or bath taken prior to dressing with the clothes provided from within the pig unit. If it is not feasible to provide a shower, a change of clothing and footwear should be 169

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required. The likelihood of an infectious agent being carried on the skin or hair can be decreased considerably by requiring that personnel not be in contact with pigs (or even other animals or other people associated with pigs) for at least overnight prior to entering the pig farm. Humans can be infected with a variety of microbes that also cause disease in pigs. These are called zoonotic agents. To preclude this possibility, humans should not be allowed access to pig farms if they are ill with serious respiratory or enteric diseases. Practically, the possibility of personnel in good health with sound personal hygiene introducing infectious agents into pig farms is rather remote.

Introduction and Removal of Pigs Replacement breeding stock should be the only new pigs allowed entry to the farm (see “Gilt Development” above). Nursery and finisher space that is suboptimally utilized must not be filled by purchasing pigs from other sources. The removal of dead pigs, cull breeding stock, and pigs to be sold poses the biggest threat to disease introduction from possible contaminated transport vehicles. Ideally, dead pigs should be incinerated, placed in deep decomposition pits, or composted on the site where death occurred. If this is not possible, the locus personnel must be provided with a transport vehicle to transfer the dead pigs to a location where the animals can be collected by a dead-removal transport vehicle. A refrigeration unit placed on a double-sided loading dock is preferred for this transfer. The locus personnel can place the dead pigs in the refrigerated unit for the dead-removal personnel to collect at another time. Cull animals should be removed via a load-out chute. A common mode of introduction of disease is via contaminated transport vehicles used to remove cull animals. Precautions regarding cleaning and disinfection of the load out should be according to the standard procedures given above.

Prevention of Horizontal Introduction of Infectious Agents from Outside the Multi-Site System To prevent horizontal introduction of infectious agents, the manager must develop procedural guidelines for all individuals involved in the operation, including owners, senior managers, farmworkers, and visitors. In the author’s experience, pig introduction and removal and/or transport vehicles are the most common modes of introduction of new infectious agents into a farm. Unfortunately, there are many other ways that infectious agents can be introduced, including semen, feed, water, other species of animals, birds, rodents, and pit/lagoon nutrient application equipment. An alert team of personnel can prevent many possible introductions of infectious agents. All personnel must be delegated the responsibility and have the authority to both question and prevent (when appropriate) any threat to biosecurity. See Reeves (1996) and Harris and Alexander (1999) for detailed discussions regarding specific biosecurity measures applicable to all pig-farming operations.

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Prevention of Horizontal Intra-site Transfer of Infectious Agents The biosecurity measures addressed above also apply to preventing intra-site transfer of infectious agents (movement between loci within a site). Precautions to be taken against intra-site transfer vary with the type of multi-site system and the particular stage of production in question. For example, in a three-site (single-locus) system, transfer of infectious agents from room to room within a building or from building to building within a locus can be unavoidable. There also are situations, such as when isowean pigs originate from multiple sources, where owners and/or management decide not to take precautions against intra-site transfer. Site 1 (Breeding Production Stage) — In three-site (multi-source) systems, there has been considerable debate regarding what is referred to as “stabilization of the disease status in all source farms.” Recent research suggests that mixing isowean pigs from multiple sources results in poorer feed conversion and rate of gain. One solution is to consider the four loci (e.g., four breeding production stage complexes at different and isolated locations) of site 1 to be one locus. In this case, no precautions need to be taken regarding movement of personnel, pigs, and vehicles between the four farms. If needed, open and/or pregnant gilts could be moved between farms to fill gestating crates and/or farrowing crates. Also, all incoming stock could be isolated and acclimatized in a common area, then be distributed simultaneously to all sow farms when they are released for introduction. The countering view in the debate centers around what action plan to take if a severe disease occurs in one sow farm but not in the others. Does the manager spread the disease to all sow farms and increase the possible negative economic impact of the disease? Does the manager continue sending the isowean pigs to nurseries in the system or somehow divert these pigs out of the production flow? The answers to these questions and determining which side of the debate is correct depends primarily on the purpose of the production system and the nature of the diseases present. It is suggested that the reader refer to Chapters 3, 4, and 5 for insight and information regarding these decisions. Site 2 (Nursery Production Stage) or Site 3 (Finisher Production Stage) or Sites 2 and 3 (NurFins) — In multi-site isowean systems where loci within a site of production are well isolated (separated by 0.5–1.0 mile or more), strict precautions should be taken to prevent intra-site transfer of infectious agents. The biosecurity measures discussed in preceding sections should be followed. The longer pigs have been placed in a locus, the greater the chance of contamination by an infectious agent. Therefore, the most recently placed pigs in a locus within sites 2 or 3 should be considered of highest health status unless there has been confirmation of disease by clinical observation or diagnostic testing.

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Prevention of Vertical Inter-site Transfer of Infectious Agents One of the main purposes of multi-site production is to produce an isowean pig of higher health status than its dam. Thus, the age of pigs most likely to have the highest health status in a system is the recently weaned (isowean) pig placed in a locus (building or room) at site 2. All older pigs on the farm (in theory) can have had a greater chance of exposure to an infectious agent by horizontal introduction into the system. Some producers and veterinarians have misunderstood this concept because of the frequent movement of pigs from site 1 to site 2 facilities (e.g., some farms wean pigs every day). However, pigs should be weaned in a biosecure manner that prevents the transfer of infectious agents from any other source in site 1 to the isowean pigs. For example, care should be taken not to expose the isowean pigs to any sows or piglets that are outside the farrowing room of origin. This is necessary to help ensure that each new batch of isowean pigs can achieve and maintain a higher health status than the sows in site 1. To decrease the chance of inter-site infectious-agent transfer, most multi-site production systems establish rules regarding an appropriate sequence for personnel to move from one site to another. Since the newly weaned isowean pig is considered to have the highest health status, the following sequence of people movement is recommended: • Site 2 to site 3 Can be made in the same day with shower and change of clothes between. • Site 2 to site 1 Can be made in the same day with shower and change of clothes between. • Site 1 to sites 2 or 3; site 3 to sites 1 or 2 Cannot be made within the same day; overnight downtime between sites is required. If a disease outbreak is occurring at any site or within any locus, modifications of the rules regarding the sequence of movement of people, pigs, and vehicles will likely be required.

Summary The manager of a multi-site system must have a disciplined approach to pig production. Multi-site isowean production is somewhat inflexible compared to more traditional pig farming. But multi-site systems provide the opportunity to develop a staff with each member having very specialized skills. The manager is responsible for the overall training of personnel and development of a staff of highly motivated individuals who work as a team with the welfare of the pigs in mind at all times. The key elements of managing a multi-site system are (1) the achievement of production targets; (2) proper gilt development procedures for introducing replacement breeding stock; (3) proper pig throughput in accord with the fixed assets available; (4) maximal feed utilization with minimal wastage; and (5) stringent biosecurity measures implemented for the prevention of infectious-agent transmission.

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Production targets must be reasonable and appropriate for the facility design, personnel available, genetics of the breeding stock, and transportation system in place. The manager is responsible for accurate record keeping and the analysis of records when targets are not being met. Adequate isolation and acclimatization facilities should be available to allow enough time for gilt development prior to breeding. The disease statuses of both incoming breeding stock and the existing sow herd determine the length of time required for acclimatization. Management of reproductive performance is essential for correct throughput. The goal should be to fill each pig space in the nursery and finisher with the correct number of pigs per pen based on standard square-footage allotments. Overcrowding must be avoided for proper pig growth performance and welfare considerations. Multi-site isowean production requires all-in/all-out pig flow; therefore, calculation of feed requirements for each pen or building can be predetermined. This limits overfeeding of expensive diets to early weaned pigs. All-in/all-out pig flow allows the accurate determination of feed efficiency and results in recognition of poor management related to feed wastage and husbandry. Strict biosecurity precautions are critical for preventing infectious-agent introduction and the occurrence of economically significant disease. In multi-site production, isowean pigs are usually produced with a higher health status than their dams. Thus, biosecurity measures to prevent both intra-site and inter-site transfer of infectious agents are even more important in a multi-site system.

Bibliography Armbrecht, P. 1998. Personal communication. Botner, A. 1998. Field experiences with PRRS and with the use of a live PRRS vaccine in Denmark. Proceedings of the Swine Disease Conference for Swine Practitioners, Ames, Iowa, 59–66. Britt, J. H. 1996. Biology and management of the early weaned sow. Proceedings of the American Association of Swine Practitioners, Nashville, Tennessee, 417–426. Britt, J. H. 1997. Maximizing productivity in early weaned sows. Swine Health Summit, 93–101. Connor, J. F. 1997. Gilt development, isolation, acclimatization, and synchronization. Allen D. Leman Swine Conference. Vol. 24. 1997, 60–62. Veterinary Outreach Programs, University of Minnesota, St. Paul. Connor, J. F. 1998. Wean-to-finish construction alternatives, management, and performance. Allen D. Leman Swine Conference. Vol. 24. 1997, 219–222. Veterinary Outreach Programs, University of Minnesota, St. Paul. Dee, S. A. and T. W. Molitor. 1998. Elimination of porcine reproductive and respiratory syndrome (PRRS) virus using a test and removal process. Allen D. Leman Swine Conference. Vol. 25. 1998, 187–189. Veterinary Outreach Programs, University of Minnesota, St. Paul. Dee, S. A. and R. Philips. 1997. Attempts to influence the PRRS status of replacement gilts. Allen D. Leman Swine Conference. Vol. 24. 1997, 63–68. Veterinary Outreach Programs, University of Minnesota, St. Paul. Dee, S. A. and R. Philips. 1998. Using vaccination and unidirectional pig flow to control PRRSV transmission. Swine Health and Production 6:21–25.

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DiPietre, D., L. Fuchs, and R. Tubbs. 1997. Using the DuPont model. Allen D. Leman Swine Conference. Vol. 24. 1997, 95–102. Veterinary Outreach Programs, University of Minnesota, St. Paul. Dorminy, H. 1998. Personal communication. Harris, D. L. and T. J. L. Alexander. 1999. Methods of disease control. In Diseases of Swine, 8th ed., ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor. Iowa State University Press, Ames. Heber, A. J. 1996. How far do bacteria travel in the air? National Hog Farmer, January issue 1996, 56. Hollier, D. 1979. Aspects of Swine Ecology. Gateway Press, Spring Green, WI. Jolly, R. W. 1995. Financial Troubleshooting. Iowa State University Extension Publication, 1–8. Patience, J. F. 1997. What to do when feed intake is below target: Nutritional, environmental, and management strategies. Allen D. Leman Swine Conference. Vol. 24. 1997, 130–134. Veterinary Outreach Programs, University of Minnesota, St. Paul. Pickrell, J. A., A. J. Heber, J. P. Murphy, S. C. Henry, M. M. Can, D. Nolan, F. W. Oehme, J. R. Gillespie, and D. Schoneweis. 1993. Characterization of particles, ammonia, and endotoxin in swine confinement operations. Veterinary and Human Toxicology 35:421–428. Reeves, D. E. 1996. Biosecurity for commercial swine units avoiding common pitfalls. Swine Health Summit 133–143. Sesti, L. A. and J. H. Britt. 1993. Influence of stage of lactation, exogenous luteinizing hormonereleasing hormone, and suckling on estrus, positive feedback of luteinizing hormone, and ovulation in sows treated with estrogen. Journal of Animal Science 71:989–998. Spronk, G., B. R. Kerkaert, J. D. Bobb, G. F. Kennedy, and J. L. Goetz. 1997. Multi-site production: Why this is essential to our system. Nuts and Bolts of SEW Multi-site Systems, 10–13. Preconference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota. Wade, D. 1997. Nuts and Bolts of Multi-Site Production. Nuts and Bolts of SEW Multi-site Systems, 15–19. Pre-conference symposium, Allen D. Leman Swine Conference, University of Minnesota, St. Paul. Published by Minnesota Extension Service, University of Minnesota.

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Breeding stock must be produced so that the health status of the pigs is as high as is practical. All aspects of disease, especially in the production of breeding stock, concern owners, senior managers, and farm managers. Some producers of breeding stock go to extreme measures to be sure to locate the herds in very isolated areas to decrease the chance of contamination from neighboring farms. Often, superior breeders will pay much closer attention to biosecurity measures than do most producers of slaughter pigs. Breeding stock can be successfully produced in one-site and in multi-site farms. This is particularly true when newly constructed farms are stocked with pigs that have been surgically derived and reared under very clean environmental conditions. However, no matter how carefully a herd is established and maintained, eventually the introduction of pathogenic microbes will occur (see Figure 3.1 and Table 6.10). The primary focus of this chapter is the responsibility and actions of the producer of breeding stock for maximal protection of the buyer (customer). Many times in the sale of breeding stock, the customer must be considered right when disagreements occur or mistakes are made. However, the buyer also has a responsibility when breeding stock is purchased. It is impossible for a breeder to absolutely guarantee that the pigs supplied are perfect and totally free of infectious agents. A sincere and honest buyer should take a series of ethical steps when a concern with the purchased pigs arises. These steps are: 1. Rapid communication with the supplier when something is wrong. 2. Strict isolation of all incoming purchased breeding stock and comparison of their infectious disease status to the pigs in the customer’s herd. 3. Rejection of the pigs while in isolation if the pigs do not match the health status of the pigs in the customer’s herd. If these simple steps are followed by the buyer in a responsible manner, most litigious situations can be avoided if the breeding stock supplier also responds with appropriate action in a reputable manner.

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Disease Breakdowns When infectious disease occurs or it is determined that a new infectious agent has been introduced into a herd, it is often called a “breakdown” (the deterioration of the health status of that particular farm). When and how often a breakdown will occur is difficult to predict. Factors that influence the rate of breakdowns are the pig density of the region where the herd is placed, the degree of isolation of the herd from other pig farms, the method of replacement of breeding stock, the biosecurity measures in place, the type of transport vehicles (whether owned or leased), and the feed and water supplies. An advantage of a multi-site isowean production system is that a disease breakdown may occur only in site 1. Assuming management stops the flow of isowean pigs to site 2, precautions must be taken regarding the sale of pigs from sites 2 and/or 3, but sales often can continue. In the first three-site herd established in 1988, pseudorabies virus (PRV) was introduced within a year of start-up. The PRV did not infect pigs in site 3, and more than 7000 head of breeding stock remained available for sale (see Chapter 3, “Exclusion of Specific Agents by MEW or Isowean,” and Chapter 5, “Pseudorabies”). Once an economically significant disease is introduced into a breeding stock production herd, the disposition of the herd regarding future breeding stock sales must be addressed. In some cases, the herd is simply used for slaughter-pig production (see Figure 6.10). If the owner decides to continue to produce breeding stock, a plan must be developed either to eliminate (see Table 3.9) the infectious agent from the entire farm (depop/repop, Plomgaard Method, enhanced immunity, whole herd medication and sanitation, test and removal) or exclude it via the Isowean Principle (see Table 3.2) from stage 2 and/or stage 3 production (see Chapter 3, “Elimination of Infectious Agents by MEW and Isowean”). The details of the plan will depend almost entirely upon the nature of the infectious agent and the type of rearing system. Of course, the biosecurity breach that allowed entry of the agent must be corrected as well. Whenever a disease breakdown occurs in a herd producing breeding stock, even if it appears rather mild clinically or if it is simply based on a diagnostic test result that suggests the presence of a new infectious agent, the situation must be considered carefully and an immediate plan of action must be developed for customer protection. It is important to determine the extent of the spread, if any, of the infectious agent to the customers that have been receiving breeding stock from the herd. The steps in the action plan usually include: 1. The determination of whether the herd should be closed for the sale of breeding stock permanently or temporarily. 2. Notification of customers who have recently received stock from the farm because the pigs they received may be in the incubatory stages of the disease. 3. Epidemiological investigation of customer farms to determine, if possible, when the infectious agent was introduced to each customer farm, as well as to the source farm. 4. Further diagnostic testing is usually required to determine the extent of the infection in the source farm, as well as in customer farms, and to reconfirm the diagnosis.

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5. If the herd has been closed temporarily, decisions have to be made whether or not clinical signs of the disease have disappeared and then whether or not the herd can be reopened for the sale of breeding stock. 6. If the herd is closed permanently, it is believed that an economically unacceptable infectious agent caused the breakdown and therefore pigs infected with it should not be delivered to customers. Again, the type of rearing system and the nature of the infectious agent will dictate whether the closure is temporary or permanent. In the situation of a permanent closure due to a disease breakdown, the herd usually cannot continue producing breeding stock for sale to customers until the infectious agent either has been excluded (via isowean) from breeding stock for sale or has been eliminated from the entire herd. Reputable breeders with one-site farms may have to totally depopulate the farm, clean and disinfect it, then restock it with high–health status pigs to use it as a source of breeding stock in the future. In some situations, a permanently closed herd can continue to sell breeding stock to certain customers if it is agreed among the customers that the particular disease agent causing the closure is of minor consequence or if they want to live with the particular situation. With some diseases, such as transmissible gastroenteritis and swine dysentery, it can be possible to eradicate the infectious agent from one-site herds without total depopulation. In this case, these herds can be reopened for sale of breeding stock once the organism has been eliminated (see Chapter 5, “Swine Dysentery” and “Transmissible Gastroenteritis”). The great advantage of multi-site isowean farms is that a large variety of infectious agents can be excluded from breeding stock or eradicated from the entire farm more readily than from one-site and traditional two-site farms (see Tables 3.1–3.9). To produce breeding stock, new or depopulated farms can be restocked with high–health status pigs that have been derived by surgical means, MEW, or isowean. Multi-site farms using the Isowean Principle can suffer breakdowns that result in permanent or temporary closure. However, with a multi-site farm, it is usually feasible to resume the sale of breeding stock without depopulation of the production unit. The methods of elimination of infectious agents discussed in detail in Chapters 3, 4, and 5 can be applied to eliminate various agents from the different types of multi-site farms.

Production Pyramids Prior to 1960, breeders primarily produced boars. Gilts were only purchased from breeders in conjunction with boars for the stocking of new herds. Quite often the producers of slaughter pigs purchased purebred boars that were used for natural servicing of purebred or crossbred gilts. For a time, a rotational-cross system, in which gilts were kept back as replacements and a different purebred boar was used annually to cross back onto the gilts, was very popular1. Ken Woolley, co-founder of PIC, originated the concept of a breeder 1. Currently, rotational-cross systems are enjoying a revival due to the following factors: artificial insemination, fear of diseases such as PRRS, and decreasing profit margins.

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supplying both an F1 gilt and a purebred boar simultaneously to the customer producing slaughter pigs. His approach to genetic improvement was based on the work of Professor Jay Lush at Iowa State University. Under the leadership of Ken Woolley and the consultancy advice of Tom Alexander and Maurice Bichard, PIC developed production pyramids consisting of nucleus and multiplier farms for the production of F1 gilts and purebred boars (Figure 8.1). Alexander developed the disease control principles for a production pyramid to create and maintain high–health status pigs for distribution to customers. The customer was encouraged to only utilize F1 gilts as parents; thus, all replacement animals had to be purchased from the breeding stock company rather than being produced by the customer. The marketing premise was that a breeding stock company could produce a much superior F1 female to be used in stocking new herds or as replacements than slaughter-pig producers could produce on their own. A breeder could create nucleus herds of sufficient size to allow greater selection intensity for the reproductive performance and carcass traits desired. A production pyramid is composed of a nucleus farm, multiplier farms, and the customer farms that are being supplied the breeding stock. In the 1960s and early 1970s, the nucleus farms of most breeders were composed of two or possibly three main lines of purebred animals. (Depending upon the size of the herd, other experimental or developmental lines could also be present.) Nucleus farms were run as closed herds, so new genetic material was introduced only by surgical-derivation or artificial insemination. The multiplier farm, then, received the two types of purebred animals, usually purebred landrace females

Figure 8.1 Pyramid design for the production of breeding stock. A 500-sow genetic nucleus farm has the possibility of being the genetic base for more than 1.5 million slaughter pigs. (Modified from Alexander and Harris, 1992)

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and purebred large white (Yorkshire-like) males. These were crossed at the multiplier farm to produce the F1 gilt. Extensive testing of boar and female lines occurred in the nucleus farm, with the superior lines of both sexes being retained. Most of the females were then placed in multiplier farms, while the excess purebred boars were sent both to multiplier farms and to customers. In the typical customer program, the F1 gilt was purchased from a multiplier and a purebred boar from a nucleus farm. Initially, a nucleus herd might contain 250 to 500 sows; multiplier herds ranged from 100 to 300 sows. Tom Alexander established two extremely important disease control principles of breeding stock distribution in these early days of pyramid production development. First, he insisted that customers only be supplied from one multiplier and one nucleus farm within the same pyramid. The only time that this might be changed was if the multiplier suffered a breakdown and permanent closure. Second, it was also important for a breeder to establish what Tom called straight-line distribution, in which the flow of animals was always down the pyramid. No animals could flow backward from a multiplier to a nucleus, flow horizontally to other multipliers, or flow to other pyramids (Figures 6.12 and 8.2). Breeders who failed to follow straight-line distribution quite often failed to maintain their businesses because of disease breakdowns. Beginning in the mid-1970s and continuing through the mid-1980s, the genetic improvement and distribution pyramid systems established by breeders became more complicated. For example, it was found (based on a recommendation by Lauren Christian) that a white F1 female crossed with a purebred Duroc boar would produce a female that was much heartier, at least for U.S. and Mexican conditions, and had nearly the same reproductive prolificacy as an F1 female. Simultaneously, specialized boar lines were

Figure 8.2 Straight-line distribution of breeding stock.

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developed that, when crossed on these hybrid gilts, created a more superior carcass than when the gilts were bred to purebred boars. As the size of customer farms began to increase—and the number of farms began to decrease (see Figure 6.11)—and as the genetic development programs became more sophisticated, it was necessary for nucleus and multiplier farms to become larger and larger. In some instances, specialized boar multiplier farms were created to produce highbred boars (rather than purebred boars) for natural service. Again, successful breeders maintained straight-line distribution in order to provide high–health status pigs to customers. Beginning in 1988, most newly established breeding stock production farms have been constructed as multi-site isowean systems (see Table 1.2), and many commercial farms worldwide have been modified or newly constructed as multi-site isowean systems (see Tables 1.1 and 1.3). This was soon followed by a worldwide change in the swine industry toward the use of artificial insemination rather than natural service. These two developments have had a profound impact on how breeding stock are produced today. Genetic nucleus farms generate their own replacements and can receive new genetic material from the outside via a variety of methods, including surgical derivation, embryo transfer, MEW, isowean, and artificial insemination. Daughter nucleus farms and multipliers receive their replacement female stock from a nucleus or daughter nucleus herd from within the same pyramid. Sometimes a production nucleus herd can be established and placed between the nucleus and the multiplier farms; this herd can both receive replacements from a nucleus and produce its own replacements. Today, most breeding stock production herds receive semen from an off-site boar stud and only use artificial insemination (Figures 6.12 and 8.3).

Multi-site Production Systems All the various types of one-site and multi-site production systems can produce breeding stock successfully. The type chosen by the breeder may depend on the size of the herd and its location within the pyramid of production. Both three-site (single-source, multi-loci) and NurFin isowean systems are ideal for the exclusion of specific infectious agents prior to weaning. It is not necessary to depopulate to eliminate infectious agents that may have been vertically introduced from site 1 or have been horizontally introduced into these systems because each nursery building, finisher building, and NurFin is placed on a separate and isolated locus, and as each group of pigs is removed from an isolated building, the building is thoroughly cleaned and disinfected. A disadvantage of the NurFin isowean system is that if an agent is introduced into a NurFin building, there is the possibility of contaminating more pigs. Of course, if more than one NurFin building is placed on a locus and the buildings are placed in close proximity, say, 50 to 150 feet apart, then the advantages of all-in/all-out by building can be lost, and the entire locus may have to be depopulated to eliminate a specific infectious agent. Types of multi-site systems that require the nursery and the finisher to be totally depopulated in the event of a horizontal introduction of an infectious agent are three-site 180

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Figure 8.3 The function of the various herds in a genetic improvement and production pyramid. (Courtesy of PIC, Franklin, Kentucky)

(single-locus), two-site isowean (single-locus), and two-site isowean on-site (single-locus) production. One-site and traditional two-site farms may require total depopulation for eradication of most infectious diseases.

One-site or Multi-site Herds? In genetic nucleus and production nucleus herds, which do extensive progeny testing and production of internal replacements, there have been fierce debates among veterinarians 181

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and production managers over the pros and cons of constructing one-site or multi-site herds. The multi-site isowean system could be advantageous if a horizontal introduction of an infectious agent occurred and a program needed to be developed for eradication. However, in a multi-site system, the objective of attaining offspring of a higher health status than in stage 1 production is usually achieved; therefore, if replacements are generated internally, acclimatization facilities must be provided. By contrast, in a one-site system, the offspring may have been exposed to most of the infectious agents in a herd and may not need or require acclimatization prior to entering the breeding herd.

Determination of the Health Status of Pigs Produced in a Multi-site System Traditionally, the health status of pigs produced in one-site and traditional two-site farms has been determined by a combination of the following criteria. The criteria are production performance, including reproductive performance, mortality rates, and body weight for age; frequent veterinary visits with clinical observations; necropsy of unexplained deaths; implementation of sophisticated laboratory diagnostics when clinical problems arise; diagnostic tests performed as a result of regulatory requirements for interstate shipment or export; slaughter inspection; and probably most importantly, the performance of the breeding stock in customer farms. Note that the above criteria rely more heavily on practical and observational disease monitoring rather than on specific diagnostic test results. All of these criteria also can be applied to breeding stock produced in a multi-site isowean system; however, a new dimension has been added. If an attempt is being made to elevate the health status of pigs by excluding infectious agents by isowean, then determining the presence or absence of these infectious agents prior to entry of the pigs into the customer’s herd becomes very important. Simple clinical observations, production performance records, and slaughter inspections may be inadequate. If a breeder wishes to claim the absence of a particular infectious agent from the stock sold, some form of diagnostic laboratory test may need to be performed. The type of laboratory test used to detect the presence or absence of a specific infectious agent depends on the nature of that particular agent. The major disadvantage of utilizing laboratory tests to determine health status by measuring the presence or absence of an infectious agent is the occurrence of false positive and false negative results. A false positive result may unnecessarily cause the curtailment of breeding stock shipments, while a false negative result could lead to the introduction of a possible unwanted infectious agent into a customer’s herd. The sensitivity and specificity of a laboratory diagnostic test are indications of the accuracy of that particular test. An ideal diagnostic laboratory test for a specific infectious agent would have a specificity of 100% and a sensitivity of 100%. This would mean that assuming the sample is collected properly and from the right location in the body, the test would never have a false positive reaction (specificity), and it would never have a false negative reaction or test result (sensitivity). Unfortunately, no laboratory test has an accuracy of either 100% specificity or 100% sensitivity. 182

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Table 8.1 Four Possible Diagnostic Test Results Disease Status Disease

Positive Negative

No Disease

True Positive (TP) False Negative (FN)

↓

Sensitivity =

False Positive (FP) True Negative (TN)

↓

TP TP + FN

Specificity =

TN TN + FP

Source: Modified from Lim, 1998.

It is necessary to determine the accuracy of each diagnostic test used. The sensitivity is defined as the ability of the test to correctly determine those pigs that have the agent or disease. The specificity is defined as the ability of the test to correctly determine those pigs that do not have the agent or the disease. The four possible results of a diagnostic test are (1) true positives do have the agent or disease; (2) false positives do not have the agent or disease but test positive; (3) true negatives do not have the agent or disease; and (4) false negatives actually have the agent or disease but test negative (Table 8.1). To determine these four types of results for a test, the test is run on samples from a population of known disease status. The results are then used in the following formulas: True positives × 100 Sensitivity = True positives + false negatives True negatives × 100 Specificity = True negatives + false positives

In reality, most diagnostic laboratory tests for infectious agents are best used on a herd basis. If a large enough sample of pigs is tested, and if a majority of the animals are negative or are positive, then reasonable and rational interpretation of the results will usually indicate the health status of that particular group of pigs. Unfortunately, this introduces a judgmental aspect to diagnostic laboratory testing. Most tests really should not be used on an individual pig basis.

Determination of the Health Status of Breeding Stock in Isolation It cannot be guaranteed unequivocally that the health status of animals at the time of shipment is what it appears to be based on performance criteria, observational data, and laboratory diagnostic test results. For example, an infectious agent could have been recently introduced into the farm but the manifestation of the disease may only be in the incubatory stages and not clinically apparent. Often during the incubatory stages, diagnostic laboratory tests are even less sensitive and specific. Animals also could be contaminated in transit from the breeder to the customer’s farm. 183

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Therefore, it is highly recommended that all breeding stock delivered to a customer’s farm be isolated a minimum of 3 weeks in a facility near, but not adjacent to, the customer’s pigs. Since the recipients of the breeding stock should be most concerned about the introduction of any new infectious agent into their herd, they can, with the aid of a veterinarian and a diagnostic laboratory, conduct a series of tests on the replacement breeding stock while it is in isolation. Simultaneously, a comparable number of animals of the same age in the recipient’s herd could be tested for the same infectious agents. If there are no significant differences between the two groups of pigs, it is assumed that no new infectious agent will be introduced into the customer’s herd. Any questions regarding the warranty of the health status of the breeding stock by the breeder should be addressed prior to their removal from isolation.

Laboratory Diagnostic Tests for Detection of Specific Infectious Agents There are two major types of laboratory diagnostic tests: direct and indirect. A direct test indicates the presence or absence of the infectious agent itself, usually by demonstration in or by culture from some body tissue or secretion. This type of test can be based on isolation and identification of the particular organism in laboratory cells or test tubes, or on the demonstration of the organism by some microscopic means. For example, fluorescent and electron microscopes can be used to demonstrate an infectious agent in body secretions or organs. An indirect test determines if the pig has produced antibodies against an infectious agent. First, a blood sample is collected from the pig and the serum is separated from the red blood cells. The serum contains the antibody fraction of the blood (see Chapter 4, “Antigens, Antibodies, and Immunity”) and is used to determine if an infectious agent in the pig has produced antibodies. The level of antibody is expressed as the titer. If a pig has produced antibodies to an infectious agent, it means that the infectious agent was in the pig at one time, but it cannot mean the infection still is present or ever caused a disease. In general, the direct tests tend to be of low sensitivity, but very specific. Indirect tests are likely to be very sensitive, but in some cases lack specificity. Figure 8.4 illustrates how a serological test with excellent specificity and sensitivity can still result in a few samples that are either false positive or false negative. An additional word of caution is appropriate. If a diagnostic test of high sensitivity and specificity indicates the presence of an infectious agent, it does not necessarily mean it has or will cause an economically significant disease. For example, the direct culture of Pasteurella multocida from the nasal cavity of a pig can or can not indicate that atrophic rhinitis is occurring. If the P. multocida bacterium, when subjected to further laboratory evaluation, did not possess the gene for the toxin causing atrophy of the turbinates, then the mere presence of that particular infectious agent would not justify rejection of the breeding stock in isolation.

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Figure 8.4 The distribution of antibody titers from pigs infected with and pigs not infected with the disease-causing agent. (Modified from Martin, Meek, and Willeberg, 1987)

Summary Breeding stock can be produced in one-site and any type of multi-site production systems. The major advantage of multi-site isowean systems is that infectious disease-causing agents can be more readily excluded or eradicated from these types of pig farms. If a specific infectious agent is being excluded from a breeding stock supply herd via the Isowean Principle, sophisticated diagnostic testing and interpretation of test results can be required to protect customers against the introduction of a new disease into their herds. Both the supplier and the buyer of breeding stock must communicate responsibly with one another when something is wrong with the pigs. It is essential that newly purchased pigs be placed in isolation to ascertain their infectious disease status and to compare it to the health status of the pigs in the recipient herd. Unnecessary litigation can be avoided in this manner.

Bibliography Alexander, T. 1988. Disease control: Present and future. Proceedings of the American Association of Swine Practitioners 115–126. Alexander, T. J. L. 1995. The components of pig health. In The Health of Pigs, ed. J. R. Hill and D. W. B. Sainsbury, 1–25. Longman Group Ltd., Essex, England. Alexander, T. J. L. 1998. Personal communication. Alexander, T. J. L. and D. L. Harris. 1992. Methods of disease control. In Diseases of Swine, 7th ed., ed. A. D. Leman, B. E. Straw, W. L. Mengeling, S. D’Allaire, and D. J. Taylor, 808–836. Iowa State University Press, Ames.

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Christian, L. L. 1984. Personal communication. Glock, R. D. and D. L. Harris. 1993. Disease management strategies: Treat, control, or eliminate? Proceedings of the Swine Disease Conference for Swine Practitioners, Ames, Iowa, 1–16. Harris, D. L. 1987. Quarantine before introduction of breeding stock. Pigs 3:18–19. Harris, D. L. and T. J. L. Alexander. 1999. Methods of disease control. In Diseases of Swine, 8th ed., ed. B. E. Straw, W. L. Mengeling, S. D’Allaire, and D. J. Taylor. Iowa State University Press, Ames. Lim, D. 1998. Microbiology. WCB/McGraw-Hill, Dubuque, Iowa. Lush, J. L. 1994. The Genetics of Populations. Iowa Agriculture and Home Economics Experiment Station, College of Agriculture, Iowa State University, Ames. Lush, J. L., P. S. Shearer, and C. C. Culbertson. 1939. Crossbreeding Hogs for Pork Production. Iowa Agriculture Experiment Station Bulletin 380. Martin, S. W., A. H. Meek, and P. Willeberg. 1987. Veterinary Epidemiology: Principles and Methods. Iowa State University Press, Ames. Muirhead, M. R. and T. J. L. Alexander. 1997. Managing Pig Health and the Treatment of Disease. 5M Enterprises Ltd., Sheffield, England. Ollivier, L. 1998. Genetic improvement of the pig. In The Genetics of the Pig, ed. M. F. Rothschild and A. Ruvinsky, 511–540. CAB International, New York. Patterson, C. T. 1999. Personal communication. Patterson, C. T. and Prahl, M. M. 1995. Veterinarians in the courtroom. Unpublished presentation at the 1995 A. D. Leman Conference, St. Paul, Minnesota. Tyler, J. W. and J. S. Cullor. 1989. Titers, tests and truisms: Rational interpretation of diagnostic serologic testing. Journal of the American Veterinary Medicine Association 194:1550– 1558.

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9. Standardized Nomenclature, Alphanumeric Notation, and Diagrams

Pig farming operations vary considerably in the types and locations of rearing facilities and in pig flow. The evolution of modern-day multi-site systems has caused some confusion regarding the terminology used to describe pig farms. For example, many terms are used synonymously for the word isowean, including modified medicated early weaning (MMEW), segregated early weaning (SEW), age-segregated rearing (ASR), isolated weaning, and segregated disease control (SDC). In this chapter, I propose a standardized nomenclature for one-site and multi-site rearing systems. I also present diagrams and a system of alphanumeric notation that allows detailed descriptions of pig farming operations in terms of the stages of production and their location, pig flow, sites, loci, and management practices. Owners, managers, farmworkers, animal scientists, nutritionists, geneticists, agricultural engineers, extension personnel, veterinarians, regulatory agencies, lawyers, and lending institutions may find standardized nomenclature, alphanumeric notation, and diagrams useful for describing pig farms. Pig farms can be described using alphanumeric notation only, which facilitates the establishment of computerized information and databases. During the writing of this book, I was seeking an alternative term for the word site when it is used to denote the location of a building. Site may mean the specific location of a building within a site to one person but may mean a stage of pig production to someone else. My wife suggested the word locus (plural: loci). Further discussions with several individuals, such as Steve Henry, who suggested that Global Positioning Satellite (GPS) technology be included, resulted in the text for this chapter. Throughout the preceding chapters, I have used terms as they are defined in Chapter 1. Many of the terms proposed in Chapter 9 remain as defined in Chapter 1; however, some have been deleted (see “Recommendations for the Use of Certain Terms,” later in this chapter). Some terms as defined in the glossary of Chapter 72 in the eighth edition of Diseases of Swine have been either discontinued or redefined. Pertinent terms recommended by the National Pork Producers Council (NPPC) in the National Pork Production and Financial Technical Manual, edited by Will Marsh, have been included.

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Terminology To create an alphanumeric system that both describes systems and facilitates computer entry, many terms are accompanied by an abbreviation or by a symbol. Nomenclature for Pig Production Rearing Systems. A method consisting of terms, diagrams, and alphanumeric notation for describing in detail the design, location, and management of both one-site and multi-site pig production rearing systems. Stages of Production (SP). The three stages of production are (1) breeding production stage, (2) nursery production stage, and (3) finisher production stage. Stage 1 (Breeding Production Stage). Production stage in which breeding females and boars are kept and managed for the purpose of producing weaned pigs. Breeding (Br), Gestation (Ge), and Farrowing (Fa) [BrGeFa]. The substages of breeding production that involve the adult females and males, including the mating (both by natural service and artificial insemination) and the gestating of sows. The farrowing substage also includes the farrowing and lactation of the young suckling piglets. Stage 2 (Nursery Production Stage). Production stage associated with nursery pigs. Pre-nursery (PreN). A substage of nursery production for rearing the young pig immediately after weaning. It is excluded from most pig farms. Nursery (N). A substage of nursery production for rearing the young pig either immediately after weaning or after the pre-nursery stage. The pigs are usually held in the nursery for 7 weeks. Stage 3 (Finisher Production Stage). Production stage associated with finisher pigs. Grower (G). A substage of finisher production for rearing the pig immediately after the nursery. It is excluded from most pig farms. Finisher (F). A substage of finisher production for rearing the pig either immediately after the nursery stage or after the growing stage until it is either slaughtered for meat consumption or used as a breeding female or male. Site (S). A site number indicates the placement for the various stages of production. Pigs may be reared on one or more locations (loci) within a site. Locus or Loci (L). Loci indicate the number of geographic locations for each stage of production at each site. There may be one or more buildings at each locus. Single Locus (SL). A stage of production is placed entirely on one geographic location. Multi-loci (ML). A stage of production is placed on more than one geographic location. Source of Pigs. In multi-site production, source refers to either the number of loci in stage 1 producing isowean pigs, or to the number of loci in stages 1 and 2 producing feeder pigs. 188

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Single Source. The pigs originate from only one locus of stages 1 and 2. Multi-sources. The pigs originate from more than one locus of stages 1 and 2. Medicated Early Weaning (MEW). Pregnant sows are farrowed in isolation in all-in/all-out farrowing rooms away from the source herd. At about 5 days of age, piglets are weaned into an isolated nursery on a separate site. At 6 to 10 weeks of age, the pigs are transferred to an isolated grower/finisher on a third site. Prior to farrowing and during lactation, sows are medicated against the specific bacteria that are to be eliminated. The piglets are medicated during suckling and for the first 10 days after weaning. Where appropriate, the sows also can be vaccinated 4–6 weeks prior to farrowing. This is the classical procedure for MEW, but several variations of it have been applied successfully. Isowean. Similar to MEW except that the sows are farrowed in the source herd in the normal way rather than in an isolated farrowing house. Also, the weaning age is variable (up to 21–28 days of age), depending on the infections to be eliminated. Other terms that have been used for isowean are modified medicated early weaning (MMEW), segregated early weaning (SEW), segregated weaning, age-segregated rearing (ASR), isolated weaning, and segregated disease control (SDC). The term isowean is often used more widely to cover any system involving segregated or isolated weaning, which is how it is used in this book. (See also Isowean Principle.) Isowean Principle. The principle that piglets remain free from most of the serious potential pathogens endemic in a herd until after weaning (when, in traditional systems, they are sequentially exposed to pathogens from older, growing pigs). Furthermore, the piglets are likely to remain free of these pathogens if they are raised in isolated groups away from their cohorts and other age groups. This principle is the basis on which modern-day multi-site pig production systems have been developed. One-site Production (Farrow-to-Finish). All three stages of production take place on site 1 in one locus. Historically, this is the way pigs have been raised (Figures 2.1, 9.1, and 9.2). Two-site Production Traditional Two Site. Two-site production where stages 1 and 2 are placed on site 1 at one at one or more loci, and stage 3 is placed on site 2 at one or more loci. Prior to 1989, this was the only type of two-site production system (Figures 2.2, 9.3, and 9.4). The Isowean Principle does not apply. Two-site Isowean. Two-site production where stage 1 is placed on site 1 at one or more loci, and both stages 2 and 3 are placed on site 2 at one or more loci (Figures 2.13, 2.14, 9.5, and 9.6). The Isowean Principle applies between sites 1 and 2. NurFin Isowean. Each batch of weaned pigs is placed in a NurFin (wean-to-finish) building at site 2 (Figures 2.16, 2.17, 9.7, and 9.8). The Isowean Principle applies between sites 1 and 2. 189

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Figure 9.1 Key for diagrams of pig-rearing systems (Figures 9.2–9.13).

Figure 9.2 One-site production.

Figure 9.3 Traditional two-site production (single source, single locus).

Nursery/Finish (NurFin) Building (NF). Isowean pigs placed in a building equipped to provide adequate comfort, waterers, feeders, and pens for pigs ranging in age from 2 to 3 weeks through slaughter weight (Figures 2.16 and 2.18). Other terms that have been used for nursery/finish buildings are nursery/finish and wean-to-finish. Two-site Isowean On-site Production. Stages 1 and 2 are on one locus but are well isolated from one another. Usually a waste-storage lagoon and/or freshwater-storage

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Figure 9.4 Traditional two-site production (multi-source, single locus).

Figure 9.5 Two-site isowean production (single source, single locus).

Figure 9.6 Two-site isowean production (multi-source, multi-loci).

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Figure 9.7 NurFin isowean production (single source, multi-loci).

Figure 9.8 NurFin isowean production (single source, multi-loci).

pond separate the buildings for each stage. Stage 3 production occurs in isolated loci containing all-in/all-out finisher buildings (Figures 2.15 and 9.9). Three-site Production Three Site. Each stage of production is located on a separate site, referred to as sites 1, 2, and 3 respectively. Each stage of production can be on one or more loci within a site (Figures 1.3, 9.10, 9.11, and 9.12). The Isowean Principle applies between sites 1 and 2. The breeding production stage in traditional two-site, two-site isowean, and three-site farms may be on more than one loci within site 1 (can originate from more than one 192

9. Nomenclature, Notations, and Diagrams

Figure 9.9 Two-site isowean on-site production (single locus).

Figure 9.10 Three-site production (single source, single locus).

source). In addition, these systems may place pigs in the nursery and finisher production stages on more than one locus within sites 2 and 3. Therefore, these terms are used to indicate whether pigs originate from a single source or multi-sources in site 1 and if a single locus or multi-loci are used in sites 2 and 3. Outdoor Isowean Production. Stage 1 production occurs in an extensive pasture system with weekly farrowings all year-round. Nursery and finisher buildings are placed in isolated loci (Figures 2.19 and 9.13). The Isowean Principle applies between sites 1 and 2. Multi-site Pig Production. A blanket term to cover any arrangement of sites and loci, including all types of two-site and three-site production systems. The Isowean Principle may or may not apply. Multi-site Isowean Production. A blanket term to cover any arrangement of sites that incorporates the Isowean Principle, including the various possible configurations for two-site and three-site production. Isowean pigs may be from single or multiple sources. This type of production also is referred to as modern-day multi-site production. 193

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Figure 9.11 Three-site production (single source, single locus).

All-in/All-out Pig Flow (AIAO) by Site, Locus, Building, or Room. Populating a site, locus, building, or room in one day with pregnant sows at term or with pigs of the same age. The site, locus, building, or room is depopulated completely at the appropriate time (usually 2–3 weeks of age for piglets nursing sows, 6–7 weeks later for nursery pigs, and < 15 weeks later for slaughter pigs), cleaned, disinfected, dried, and left empty for 5–7 days before it is repopulated (Figure 2.20). Continuous Pig Flow (CF) by Site, Locus, Building, or Room. An alternative of all-in/all-out pig flow. The site, locus, building, or room is never (or only rarely) depopulated. Since pigs are always present, there is no opportunity for total cleaning and disinfecting of the facility (Figure 2.20). 194

9. Nomenclature, Notations, and Diagrams

Figure 9.12 Three-site production (multi-source, multi-loci).

Figure 9.13 Outdoor isowean production (single source, single locus).

Single-sex Feeding (SSF). The placement of pigs of one sex in a room or a building. Number of Pigs (NP). The number of growing pigs at a specific room, building, or locus. Number of Sows (NS). The number of sows in the first stage of production. Weaning Age (WA). The age in days when the pigs are weaned from the sow. Office (FF). A specific area or building used for personnel and record keeping. An office may or may not contain the changing area or shower. Shower (S). A specific area or building for taking a bath with a complete change of clothing. Changing Room (CR). A specific area or building for making a complete change of clothing. 195

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Incinerator (I). An oven for the decomposition of dead pigs and placentas by heat. Dead Pit Storage (DPS). A pit (about 12 feet by 12 feet) in the ground in which dead pigs and placentas are placed for decomposition. Dead Storage and Transfer (DST). A special platform (and usually a refrigeration storage unit) for storage and transfer of dead pigs and placentas to a vehicle to transport the material away from the farm. Compost (C). A special area or building designated for composting animal waste, dead pigs, and placentas. Lagoon (Lag). A waste-storage area that decomposes waste either aerobically or anaerobically. Earthen or Concrete Basin (ECB). A belowground-level storage system that decomposes waste primarily anaerobically. Anaerobic Digester (AD). A system for decomposing waste by anaerobic digestion. Some are equipped to capture methane gas. Waste-storage Aboveground (WSAG). An aboveground waste-storage container. Pits (P). The waste-holding area under slatted-floored buildings. These can be either deep pits (DP) or shallow pits (ShP). Gutter Flush (GuFl). A system of flushing shallow pits or gutters with water. The gutters may be open (no slats). Recycled Lagoon Water (RCL). Water from the lagoon is used to flush gutters or shallow pits. Load-Out (LO). A facility for transferring pigs from the farm to a transport vehicle (Figures 6.16 and 6.17). Freshwater Flush (FWF). Freshwater is used to flush gutters or shallow pits. Water Supply (WS). The source of water for the farm if it is in a storage container of some type. Power Ventilation (PV). Building is totally enclosed and ventilated with fans. Curtain Sided (CS). Building can be opened for natural ventilation or the curtains can be closed. Open Front (OF). Building has an open front and the pigs walk out onto either a dirt lot or a concrete floor. The lot may or may not be covered by a roof. Boar Stud (BS). A specific area or building for holding boars and where semen is collected for artificial insemination. Isolation for Breeding Stock (IB). A specific area or building for isolating incoming breeding stock prior to entry into the herd. The IB can also be used for acclimatization. 196

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Genetic Nucleus (GN). Select great-grandparent (GGP) males and females for genetic improvement by both quantitative genetics and molecular genetics. Produce GGPs for the production nucleus plus GGP and grandparent (GP) boars for AI studs. Production Nucleus (PN). Production of purebred lines for daughter nucleus herds and pure and crossbred products for boar multiplication and studs. Daughter Nucleus (DN). Production of crossbred GP products for gilt multiplication. Boar Multiplier (BM). Contains crossbred GP lines for production of parent boars for commercial farms. Gilt Multiplier (GM). Contains crossbred GP lines for production of parent gilts for commercial farms. Commercial Farm (CF). Contains crossbred parent lines for the production of slaughter generations. Global Positioning System (GPS). Satellite constellation information transmitted to a receiver situated at a specific building within a locus gives the position of the building in degrees of latitude and longitude. The buildings must be separated by 30 feet.

Key to Alphanumeric Notations The alphanumeric notation system, which uses abbreviations, numerals, and symbols to describe the location, design, and management of pig farming operations, is designed to be used alone but also can be used with diagrams and photographs. The notation can be very brief (Figure 9.10) for use as an adjunct to diagrams and photographs, or it can be extremely detailed (Figure 9.11) and include such information as pig throughput and single-sex feeding. Site (S) A written numeral before the word site refers to the type of production system, as in two site or three site. There are two sites in a two-site system (Figures 2.2, 2.13–2.16) and three sites in a three-site system (Figures 1.3, 2.7, 2.9, 2.11, 2.12, and 2.19). An Arabic numeral after the letter S refers to the site of the production system (Figures 9.2–9.13). Stage of Production (SP ) Arabic numeral(s) after the letters SP refer to the stage(s) of production present at that particular site (Figures 9.2–9.13). Locus (L) Arabic numeral after the letter L refers to the number of loci at each site (Figures 9.2–9.13). Buildings (B) Arabic numeral after the letter B refers to the number of buildings at each locus (Figures 9.6, 9.9, 9.11, and 9.12). 197

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Breeding and Gestation (BrGe) Arabic numeral after the letters BrGe refers to the number of breeding and gestation buildings at each locus (Figure 9.11). Farrowing (Fa) Arabic numeral after the letters Fa refers to the number of farrowing buildings at each locus (Figure 9.11). Pre-Nursery (PN ) Arabic numeral after the letters PN refers to the number of pre-nursery buildings at each locus (Figure 9.11). Nursery (N ) Arabic numeral after the letter N refers to the number of nursery buildings at each locus (Figure 9.11). Grower (G ) Arabic numeral after the letter G refers to the number of grower buildings at each locus (Figure 9.11). Finisher (F ) Arabic numeral after the letter F refers to the number of finisher buildings at each locus (Figure 9.11). Nursery/finish Building (NF ) Arabic numeral after the letters NF refers to the number of wean-to-finish buildings at each locus (Figures 9.7 and 9.8). Hoop or Hut Buildings (H ) /H following the letter B refers to the use of hoop or hut buildings at each locus; a numeral can also be used to designate the number of buildings per locus at each site (Figure 9.13). All-in/All-out (AIAO) The letters AIAO refer to the use of all-in/all-out pig flow. After AIAO, the / symbol followed by R (room), B (building), or L (locus) indicates the pig flow is all-in/all-out by room, building, or locus (Figure 9.11). Continuous Pig Flow (CF ) The letters CF refer to use of continuous pig flow. After AIAO, the / symbol followed by R (room), B (building), or L (locus) indicates the pig flow is continuous flow by room, building, or locus. On-locus Well-separated Buildings (∅) The ∅ symbol indicates buildings on a locus that are separated by more than 100 yards and/or by placement directly across from a waste-storage lagoon (Figure 9.9). Global Positioning System (GPS) The letters GPS followed by latitude and longitude coordinates in brackets [ ] indicates the geographic position of either a structure within a locus or the locus itself (Figure 9.11). 198

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Diagrams Diagrams of production systems can be used alone or as an adjunct to alphanumeric notation. As with alphanumeric notation, diagrams can be extremely detailed or rather simple, depending on their purpose or use. In the diagrams, shades of a color and stippling depict the age of pigs in the various stages of production (Figure 9.1). White is used for structures not containing pigs. In some cases, it may be necessary to use abbreviations to denote specific structures, such as isolation buildings (IB) and boar studs (BS). Alphanumeric notation can be used in diagrams to indicate such things as weaning age; throughput; number of pigs per room, building, or locus; GPS coordinates; and singlesex feeding.

Examples of Alphanumeric Notation and Diagrams One-site Production (S1=SP1-2-3,L1) The alphanumeric notation and accompanying diagram (Figure 9.2) indicate that stages 1, 2, and 3 of production are on one site but do not give details about the number of buildings per locus. (Compare Figure 9.2 with Figure 2.1.) Traditional Two-site Production (Single Source, Single Locus) (S1=SP1-2,L1; S2=SP3,L1) The alphanumeric notation and accompanying diagram (Figure 9.3) indicate that stages 1 and 2 are on one locus within site 1 and stage 3 is on one locus within site 3 but do not give the number of buildings per locus. (Compare Figure 9.3 with Figure 2.2.) Traditional Two-site Production (Multi-source, Single Locus) (S1=SP1-2,L2; S2=SP3,L1) The alphanumeric notation and accompanying diagram (Figure 9.4) indicate the stages of production are on two sites but do not give the number of buildings per locus. Stages 1 and 2 are on more than one locus (multiple-source feeder pigs) within site 1; stage 3 is on one locus within site 2. Two-site Isowean Production (Single Source, Single Locus) (S1=SP1,L1; S2=SP2-3,L1) The alphanumeric notation and accompanying diagram (Figure 9.5) indicate the stages of production are on two sites but do not give the number of buildings per locus. Stage 1 is on one locus within site 1; stages 2 and 3 are on one locus within site 2. (Compare Figure 9.5 with Figure 2.13.) Two-site Isowean Production (Multi-source, Multi-loci) (S1=SP1,L2; S2=SP2-3,L8,B3 [1N,2F]) The alphanumeric notation and accompanying diagram (Figure 9.6) indicate the stages of production on two sites. Stage 1 is on two loci within site 1; stages 2 and 3 are on eight loci within site 2. There is no information regarding the number of buildings at site 1; however, details are given about the number of buildings within each locus at site 2. L8,B3[1N,2F] indicates one nursery and two finisher buildings are at each of the eight loci. (Compare Figure 9.6 with Figure 2.14.) 199

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NurFin Isowean Production (Single Source, Multi-loci) (S1=SP1,L1; S2=SP2-3,L24,NF1) The alphanumeric notation and accompanying diagram (Figure 9.7) indicate the stages of production on two sites. Stage 1 is on one locus within site 1; stages 2 and 3 are combined within one building on 24 isolated loci within site 2. There is no information regarding number of buildings at site 1; however, details are given about the number of buildings within each locus at site 2. L24,NF1 indicates one NurFin building is at each of the 24 loci. (Compare Figure 9.7 with Figure 2.16.) NurFin Isowean Production (Single Source, Multi-loci) (S1=SP1,L1; S2=SP2-3,L6,NF4) The alphanumeric notation and accompanying diagram (Figure 9.8) indicate the stages of production on two sites. Stage 1 is on one locus within site 1; stages 2 and 3 are in six loci within site 2. There is no information regarding number of buildings at site 1; however, details are given about the number of buildings within each locus at site 2. L6,NF4 indicates four NurFin buildings are at each of the six loci in site 2. (Compare Figure 9.8 with Figures 9.7 and 2.16.) Two-site Isowean On-site Production (Single Locus) (S1=SP1-2,L1,B2∅; S2=SP3,L1,B2) The alphanumeric notation and accompanying diagram (Figure 9.9) indicate the stages of production on two sites. Stages 1 and 2 are on site 1. B2∅ indicates that the two buildings at site 1 are separated by either a lagoon or a distance of greater than 100 yards, thus the Isowean Principle applies. Stage 3 is on one locus within site 2. (Compare Figure 9.9 with Figure 2.15.) Three-site Production (Single Source, Single Locus) (S1=SP1,L1; S2=SP2,L1; S3=SP3,L1) The alphanumeric notation and accompanying diagram (Figure 9.10) indicate the stages of production on three sites. Stage 1 is on one locus within site 1; stage 2 is on one locus within site 2; and stage 3 is on one locus within site 3. This was the design of the first three-site farm built by Chuck Sand in 1988. (Compare Figure 9.10 with Figures 1.3 and 9.11.) Three-site Production (Single Source, Single Locus) (GM,S1=SP1,L1[NS=2000]; S2=SP2,L1[WA=17,NP=6000]; S3=SP3,L1]NP=16,000]) The alphanumeric notation and accompanying diagram (Figure 9.11) give detailed information, including the nature of the facilities, numbers of pigs housed, location of the loci, the waste-handling system, and pig flow. (Compare Figure 9.11 with Figures 1.3 and 9.10.) The farm is a gilt multiplier (GM) with the first stage of production (SP) on site 1, the second stage on site 2, and the third stage on site 3. Each site has one locus (L). There are 2000 sows (NS) at site 1, 6000 pigs (NP) at site 2 that are being weaned at 17 days of age (WA), and 16,000 pigs at site 3 (NP). The following further notation on each site includes the Global Positioning System (GPS) coordinates.

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Site 1: (GPS=42°03′N93°51’W),B12(2FFS,2I,4BrGe[CS],4Fa[AIAO/R,PV],[DP]); Site 2: (GPS=42°00′N93°37′W),B9(1FFS,1I,4PN[AIAO/R],3N[AIAO/R,PV][ShP,FWF,Lag]); Site 3: (GPS=42°26′N93°52′W),B18(1FFS,DST,5G[AIAO/B,CS],11F[AIAO/B,CS,SSF][GuF,RCL,Lag] 1LO) Site 1 has 12 buildings (B), including two offices and showers (FFS), two incinerators (I), and four breeding (Br) and gestation (Ge) buildings that are curtain sided (CS). The pig flow in the four farrowing (Fa) rooms is all-in/all-out (AIAO) by room (R) and the farrowing rooms are power ventilated (PV). All the buildings with pigs have deep pits (DP). Site 2 has nine buildings: one office and shower facility, one incinerator, four prenursery (PN) buildings and three nursery (N) buildings that are all-in/all-out by room and power ventilated. The pig buildings have shallow pits (ShP), freshwater flush (FWF), and a lagoon (Lag). Site 3 has 18 buildings, including one office and shower facility, and one dead storage and transfer (DST) area. The five grower (G) buildings, and 11 finisher (F) buildings are curtain sided (CS). The pig flow in the grower and finisher buildings is all-in/allout by building and the pigs are separated by sex (SSF). The gutters in the pig buildings are flushed (GuF) with recycled lagoon water (RCL). There is a load-out (LO) building at site 3. Three-site Production (Multi-source, Multi-loci) (S1=SP1,L2; S2=SP2,L8[AIAO],B1; S3=SP3,L8[AIAO],B2). The alphanumeric notation and accompanying diagram indicate the stages of production on three sites. Stage 1 production is on more than one loci within site 1; stage 2 is on more than one loci within site 2; stage 3 is on more than one loci within site 3. The number of buildings on the two loci at site 1 are not indicated. L8[AIAO],B1 indicates that each locus in site 2 has one nursery building. L8[AIAO],B2 indicates that each locus at site 3 has two finisher buildings. L8[AIAO] indicates that the pig flow per locus is all-in/all-out. (Compare Figure 9.12 with Figure 2.9). Outdoor Isowean Production (Single Source, Single Locus) (S1=SP1,L1,B/H; S2=SP2,L1,B1; S3=SP3,L1,B1). The alphanumeric notation and accompanying diagram (Figure 9.13) indicate the stages of production on three sites. Stage 1 production is on one locus within site 1 in outdoor lots with huts for housing; stage 2 is in one locus within site 2; and stage 3 is in one locus within site 3. (Compare Figure 9.13 with Figure 2.19.)

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Recommendations for the Use of Certain Terms It is recommended that the use of the following terms in bold letters continue to be used: Isowean Reasons to discontinue using the following terms that are synonymous with isowean: Segregated Early Weaning (SEW) and Modified Medicated Early Weaning (MMEW) Both terms contain the words early weaning, which imply the pigs must be weaned early as a method for accomplishing the Isowean Principle. Early weaning is not necessary for successful implementation of the procedure. Medication also is not necessary. Initially, the word isowean was a registered service mark of PIC (Franklin, Kentucky), but PIC relinquished the exclusive use of this term so it would be available for general use by the swine industry. Segregated Disease Control (SDC) This term implies that disease is being segregated, not the pigs. Disease control is not the only benefit of isowean. Age-segregated Rearing (ASR), Segregated Weaning, and Isolated Weaning These terms are no longer used very frequently. The term isowean has the same meaning. Reasons for the retention and use of the word isowean: 1. The first use and description of the term MMEW was in 1988. 2. The first use and description of the term isolated weaning was in 1990. The reason for discontinuing the use of MMEW is because early weaning and medications are not required for the benefits of isowean to be realized. 3. The term isowean was derived from the term isolated weaning. Isolated weaning more clearly describes the Isowean Principle. 4. PIC has released the use of the term isowean to the general public. Isowean is no longer a registered service mark or trademark of PIC. 5. The terms SEW and MMEW emphasize “early weaning,” which is not necessary for infectious-agent elimination or for improved production performance. The term SEW was first published in 1995 by Rodney Goodwin in a report by the National Pork Producers Council regarding the terminal sire line evaluation program. The term isowean was not used by NPPC due to its registered trademark status at the time. Three-site Production or Three Site Reasons to discontinue using the following terms that are synonymous with three site: Three-site Isowean Production Three site implies that the Isowean Principle is being applied. Therefore, there is no need for using the term isowean in conjunction with the term three site.

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Multiple-site Production or Multiple-site Isowean Production These terms imply a double meaning for the word site. Site only refers to a specific location when one stage of production is placed on one locus. If a stage of production is placed on more than one locus, the word site should not be used to indicate a locus. Thus, in a two-site isowean system, site 1 is stage 1 and site 2 includes stages 2 and 3, while in a three-site system, site 1 includes stage 1, site 2 includes stage 2, and site 3 includes stage 3. Use of the terms locus and loci predispose the need for the use of the term multiple in referring to the isolated locations on which the buildings may be placed within a site. When the terms single source and multi-source, single locus and multi-loci are used in conjunction with the term three site, the actual design of the multi-site system is clearer. Multi-site and Multi-site Isowean Multi-site and Multi-site Isowean should be retained as blanket terms. Multi-site Pig Production This term applies to any arrangement of sites and loci, including all types of two-site and three-site production systems. The Isowean Principle may or may not apply. Multi-site Isowean Production This term applies to any arrangement of sites that incorporate the Isowean Principle, including the various possible configurations for two-site and three-site production. Isowean pigs may be from single or multiple sources. This is also referred to as modernday multi-site production.

Summary A system of standardized nomenclature, alphanumeric notation, and diagrams for describing one-site and multi-site pig farms has been developed. Terminology as recommended by the National Pork Producers Council in the National Pork Production and Financial Standards Technical Manual, edited by Will Marsh, has been incorporated.

Bibliography Alexander, T. J. L., K. Thornton, G. Boon, R. J. Lysons, and A. F. Gush. 1980. Medicated early weaning to obtain pigs free from pathogens endemic in the herd of origin. Veterinary Record 106:114–119. Connor, J. F. 1998. Wean-to-finish construction alternatives, management, and performance. Allen D. Leman Swine Conference. Vol. 25. 1998, 219–222. Veterinary Outreach Programs, University of Minnesota, St. Paul. Goodwin, R. N., and S. Burroughs. 1995. NPPC Terminal Sire Line National Genetic Evaluation Results. National Pork Producers Council, Des Moines, Iowa. Harris, D. L. 1988a. Alternative approaches to eliminating endemic diseases and improving performance of pigs. Veterinary Record 123:422–423.

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Harris, D. L. 1988b. New approaches for the elimination of infectious diseases from swine. Proceedings of the 92nd Annual Meeting of the U.S. Animal Health Association, Little Rock, Arkansas, 416–426. Harris, D. L. 1990. Isolated weaning—Eliminating endemic disease and improving performance. Large Animal Veterinarian 10–12. Harris, D. L., and T. J. L. Alexander. 1999. Methods of disease control. In Diseases of Swine, 8th ed., ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor. Iowa State University Press, Ames, Iowa. Harris, I. T. 1998. Personal communication. Henry, S. C. 1998. Personal communication. National Pork Producers Council. 1998. National Pork Production and Financial Standards Technical Manual, edited by Will Marsh. National Pork Producers Council, Des Moines, Iowa.

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The utilization of the Isowean Principle (the weaning of pigs in isolation away from the adult population in the herd) will continue to increase. The definite trend toward larger but fewer operations (see Figure 6.11) virtually assures that most new construction and renovation of pig-rearing facilities will be multi-site production (see Table 1.1). Low-cost extensive outdoor pig-rearing systems may increase in the short term, depending on available capital, particularly for traditional producers, and will rely upon the Isowean Principle as well. Currently, there are movements in North and South America, Europe, and Asia to place pig farms in geographic areas of low human and pig density. Societal concerns regarding environmental issues of waste management (primarily malodors and water contamination) are the main reasons for this movement. The placement of herds away from humans and other pigs will continue well into the 21st century. However, eventually new expansion and existing pig operations will co-exist compatibly near residential areas that are proximal to a source of available pig food (corn and soybeans). As pig farms have become fewer in number and larger in size, a decreasing proportion of the human population has become involved in pork production. This fact alone will have a tremendous impact on how pigs are raised and cared for in the next century.

Societal Changes, the Demanding Consumer, and Human Medicine In the United States, the average life expectancy is 76 years. Due to the emergence of new infectious diseases of humans and an older population, greater awareness and concern regarding human foodborne pathogens will continue. Pork consumers are more discerning about taste, tenderness, and lean content. Because so few consumers are involved in pork production, many have negative perceptions of pig farming and pork products. It is also interesting to note that this aging population’s changing medical and surgical needs will be well served by pig hormones and body parts. It is well documented that human pathogens are present in pigs and thus can occur in pork products. Furthermore, antibiotic-resistant microbes present in pigs can infect humans via pork products and possibly transfer their drug-resistant genes to pathogens 205

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already present in humans. Currently, pork is a very safe meat product due to sophisticated processing procedures and Hazard Analysis Critical Control Point (HACCP) systems in place in many countries. In addition, proper handling and cooking minimizes the possibility of human foodborne pathogens infecting humans via pork consumption. Consumers in the future, however, will expect more than the current levels of excellence. For example, the parasite Trichina spiralis has been totally eradicated from some countries’ pork supply but not from others. In Denmark, the first farm-level Salmonellareduction program has been initiated by monitoring meat juice samples collected at the slaughter plant by a mix-ELISA antibody test. Under the direction of Bent Nielsen, the Danes have also begun to eradicate drug-resistant DT 104 Salmonella from infected pig farms. Although not immediately achievable, consumers will demand that pig farms be totally free of Salmonella and other common foodborne pathogens. Technologic advances associated with consumer demands regarding pork quality and human medicine will result in extremely sophisticated rearing procedures, facilities, diets, and systems for pigs in the future.

Technologic Advances in the New Millennium Four main areas of development of the facilities and systems will likely occur in the next 25 to 50 years. These are 1. 2. 3. 4.

use of sterile feed and water, use of improved building materials to achieve maximal cleaning and sanitation, positive-pressure-ventilated buildings that prevent entry of infectious agents, filtration apparatuses that remove dust, microbes, and microbial toxins from the air within the buildings, and waste-handling systems (including dietary and microbial additives) that eliminate malodors and toxic compounds.

These technical achievements may mean that pig-farm sites, loci, and buildings could be built in relatively close proximity to both one another and to human residential areas. I can readily envision a one-site isowean rearing system (Figure 10.1). There would be four stages of production—(1) breeding and gestation, (2) farrowing, (3) nursery, and (4) finishers—on one site, with each stage in close proximity to one another. A shower and complete change of clothes (or a wet suit) would be required as one passes through each air lock. Waste-handling systems would have to be designed so that no possible crossover occurs between the stages of production. Actually, sophisticated filtration and waste-handling systems already have been developed for the rearing of experimental animals for research purposes. This technology may be further developed and become more economical due to the widespread anticipated use of transgenic pigs as organ donors for humans. Presently, the descendants of transgenic pigs that possess human genes are being reared as in Figure 10.2 for xenotransplantation studies in nonhuman primates and in humans.

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Figure 10.1 One-site isowean production. Four stages of production on one locus but the stages are isolated from one another by air locks and barrier air filtration. Conceptionally, this is medicated early weaning (MEW) on one site.

Figure 10.2 Xenotransplantation production. Possible design of a facility for producing donor pigs with human genes.

Pigs housed in genetic nucleus herds will become even more valuable. Facilities housing great-grandparents will be built to maximize survival by completely preventing the entry of infectious agents and by achieving high levels of sanitation. The use of surrogate dams has been proposed for embryo transplant not only for rapid genetic improvement but also for slaughter-pig production. It is possible that such surrogate mothers would be slaughtered immediately after farrowing. In this case, isowean pigs would be placed in individual cages for rearing (pig mamas) as proposed and developed by Jim Lecce in the 1960s. In this situation, five stages of production can be visualized: (1) breeding and gestation, (2) parturition, (3) artificial lactation, (4) nursery, and (5) finishing. The removal of the piglet immediately following birth coupled with competitive exclusion probiotic microbes and more technically advanced rearing systems could allow for the production of extremely high–health status isowean pigs for slaughter. Infectious disease will still occur in even the most sophisticated and advanced rearing systems. But there will be a greater dependence on rearing procedures and disease prevention than on conventional methods of disease control. Sophisticated molecular-based biological products and procedures will be developed to decrease the current levels of drug usage.

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Summary Future pork production will bring profound developments that primarily are based on societal changes and human needs. Highly sophisticated multi-site rearing systems utilizing the Isowean Principle will be built. These systems first will be used for the production of pigs for use as human organ donors, but subsequently they will be routinely used to rear pigs for slaughter. Societal concerns about malodors and water contamination will be solved. One-site isowean rearing systems could be the basis for the routine production of pigs free of human foodborne pathogens.

Bibliography BeVier, G. 1998. Personal communication. Freese, B. 1998. Pork powerhouses 1998. Successful Farming (October):19–23. Lecce, J. G. 1975. Rearing piglets artificially in a farm environment: A promise unfulfilled. Journal of Animal Science 41:659–666. Nielsen, B., L. Ekeroth, F. Bager, and P. Lind. 1998. Use of muscle fluid as a source of antibodies for serologic detection of Salmonella infection in slaughter-pig herds. Journal of Veterinary Diagnostic Investigation 10:158–163. Nielsen, B., L. L. Sorensen, V. D. J. Mogelmose, Wingstrand.A., M. E. H. D. Johansen, and D. L. Baggesen. 1998. Eradication of multi-resistant Salmonella typhimurium DT 104 infections in Danish swine herds. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 80. Onions, D., D. K. C. Cooper, T. J. L. Alexander, C. Brown, E. Claassen, J. Foweraker, D. L. Harris, B. Mahy, A. D. M. E. Osterhaus, P.-P. Pastoret, K. Yamanouchi, and P. Minor. 1999. An assessment of the potential of xenozoonotic disease in pig-to-human xenotransplantation. Nature (Medicine): (Manuscript submitted). Piddock, L. J. V., D. J. Taylor, C. A. Hart, and A. M. Johnston. 1998. A Review of Antimicrobial Resistance in the Food Chain. Ministry of Agriculture, Fisheries, and Food, London. Tucker, A. W., and D. J. G. White. 1998. Transgenic pigs as organ donors for man. Proceedings of the 15th International Pig Veterinary Society Congress, Birmingham, England, 175–180.

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Index

Acclimatization facilities of, 151 NurFin buildings and, 163–164 procedures of, 163 Acquired antibody production, active, 80–81 ACTH (adrenocorticotropic hormone), 85 Actinobacillus pleuropneumoniae, 17 characteristics of, 66 eradication methods compared and, 63 MEW or isowean to eliminate, 69 multi-site factor in emergence of, 93 multi-site isowean procedures to eliminate, 72–74, 75 pleuropneumonia caused by, 102–104 Plomgaard method to eliminate, 90 3-site elimination of, 33–34 Actinobacillus suis, characteristics of, 66 Adrenocorticotropic hormone (ACTH), 85 Age-segregated rearing (ASR) defined, 14 as isowean synonym, 61 as multi-site rearing system, 37 term usage and, 202 See also Isowean Age variations, immunities and, 65 AI. See Artificial insemination (AI) AIAO. See All-in/all-out pig flow (AIAO) Alexander, Tom, 3, 14, 18, 61, 68, 141, 178, 179 All-in/all-out pig flow (AIAO) alphanumeric notation of, 198 disease eliminated by, 37 facilities features and, 153 finisher building closeouts and, 169 by site, locus, building, or room, defined, 13, 194 types of, 53 vs. continuous production, 39–40 Alphanumeric notation examples of, 199–201 key to, 197–198

Amass, Sandra, 18 American Association of Swine Practitioners (AASP), 18 Amino acids, antibodies and, 81, 84 Anaerobic digester (AD), 196 Antibodies. See Immunity Antigens. See Immunity Armbrecht, Paul, 19, 20, 26, 49 Arteriviridae virus, PRRS caused by, 104 Artificial insemination (AI) benefits of, 164 production pyramids and, 180 ASR. See Age-segregated rearing (ASR) Asset management, 128 Atrophic rhinitis, 15 control of, 114 diagnosis of, 113 nature of causative agent and diseases of, 111–112 prevention of, 114 transmission and spread of, 112–113 treatment of, 113 Aujeszky’s disease. See Pseudorabies virus Barcelo, Jose, 31 Barrick, Gene, 28 BeVier, Gregg, 29 Bichard, Maurice, 178 Biosecurity, 37. See also Multi-site rearing systems, management of distance requirements and, 142, 147 microbe elimination and, 68 nutrition and, 88 Boar multiplier (BM), defined, 197 Boar stud (BS), defined, 196 Boars, gene transfer by, 6 Bordetella bronchiseptica, 112 characteristics of, 66 eradication methods compared and, 63 multi-site isowean procedures to eliminate, 75

209

Index Botner, Annette, 162 Breeder-weaners, defined, 161 Breeding and gestation (BrGe), alphanumeric notations of, 198 Breeding production stage, defined, 188 Breeding stock production buyer responsibilities and, 175 disease breakdown procedures and, 176–177 health status determination and, 175 of breeding stock in isolation and, 183–184 of multi-site system pigs, 182–183 lab diagnostic tests and accuracy measurements of, 183 direct test and, 184 indirect test and, 184 titer and, 184 multi-site production systems and, 180–181, 182 production pyramids and artificial insemination and, 180 disease control principles of, 178 genetic development in, 179–180 isowean production and, 180 nucleus farms, multiplier farms and, 178–179 rotational-cross systems and, 177 straight-line distribution concept and, 179 production stages and, 6–7, 8, 10 summary regarding, 185 Brummer, Frank, 33 Buildings (B), defined, 197 Canadian isowean facilities, 28 Carrier state, defined, 58 Castro, Gonzalo, 28, 89 CF. See Continuous pig flow (CF) Changing room (CR), defined, 195 Christianson, Bill, 105, 109 Circovirus, multi-site factor in emergence of, 93 Closed-herd multiplication, 144 Clusters of determination (CD), 85 Colostrum antibodies in, 65, 89 passive immunity and, 80, 82, 89–90 Colostrum-deprivation. See Hysterectomyderivation, colostrum-deprivation (HDCD) Commercial farm (CF), defined, 197 Common infectious swine diseases control. See specific disease Compost (C), defined, 196 Connor, Joe, 27–28, 33, 50, 163 Continuous pig flow (CF) vs. all-in/all-out pig flow, 39–40

alphanumeric notation of, 198 by site, locus, building, or room, defined, 13, 194 Control of infectious swine diseases. See specific disease Coronavirus, TGE caused by, 117–118 CR (changing room), defined, 195 Curtain sided (CS), defined, 196 Cutler, Ross, 59 Cytokines, 84–85 Cytoxic T cells, 85 Dam immune status, 91 Daughter nucleus (DN), 197 Dead pit storage (DPS), defined, 196 Dead storage and transfer (DST), defined, 196 Debt management, 129 Dee, Scott, 23, 108, 163 DeKalb Swine Breeders, 6, 29 Diagrams, explanation of, 199 Direct laboratory test, defined, 184 Disease defined, 57 disease breakdowns and, 176–177 See also Immunity; Microbes; specific disease Disease control factors in, 98 See also specific disease Donadeau, Meritxell, 105 Doporto, Jose Manuel, 28–29, 31 Dorminy, Hugh, 20, 22, 28 Dotson, Earl, 34 DuPont Equation, 128 Early weaning, 3, 14. See Modified early weaning (MMEW); Segregated early weaning (SEW) Earthen or concrete basin (ECB), defined, 196 Edgerton, Sara, 17 Erysipelothrix rhusiopathiae antibodies in colostrum and, 65 characteristics of, 66 vaccination against, 93 Expense management, 129 Farrowing (Fa) alphanumeric notations of, 198 defined, 10, 188 multi-site management and, 165 snatch farrowing and, 59, 62–63 Farrow-to-finish operation, 5 See also One-site production (farrow-tofinish) Feeder-pig industry, 5 FF (Office), defined, 195

210

Index Finisher (F) production stage alphanumeric notation of, 198 defined, 10 F10 production, 53 Freshwater flush (FWF), defined, 196 Future rearing systems and facilities disease control and, 207 environmental issues and, 205 filtration and waste-handling systems and, 205 human foodborne pathogens and, 205–206 human organ donation and, 206, 207 one-site isowean systems and, 206 societal changes and, 205–206 summary regarding, 206 surrogate dam usage and, 207 technologic advances and, 206–208 Geiger, Jer, 17, 29 Genetic nucleus (GN), defined, 197 Genetics breeding stock health and, 145–146 breeding stock production pyramid and, 143, 144 closed-herd multiplication and, 144 Genetiporc Company, 28, 29 Gestation, defined, 10, 188 Gilt breeding stock, pyramid system and, 6 Gilt development, PRRS prevented by, 106–107 Gilt multiplier (GM), defined, 197 Glasser’s disease control of, 100 diagnosis of, 99 emergence of, 91, 93 multi-site factor in emergence of, 93 nature of causative agent and disease of, 98–99 prevention of, 100 transmission and spread of, 99 treatment of, 100 Global positioning system (GPS) alphanumeric notation of, 198 defined, 197 Goodwin, Rodney, 22, 23 Gramer, Marie, 105 Grower (G) alphanumeric notation of, 198 defined, 10, 188 Gutter flush (GuFl), defined, 196 HACCP (Hazard Analysis Critical Control Point) program, 155, 206 Haemophilus parasuis antibodies in colostrum and, 65 Glasser’s disease caused by, 98–100 rhinitis caused by, 112

Halbur, Pat, 93 Harris, Isabel, 34 Hazard Analysis Critical Control Point (HACCP) program, 155, 206 HDCD. See Hysterectomy-derivation, colostrum-deprivation (HDCD) Herd immunity, 90 age immunity and, 6 Hill, Howard, 22, 24–25 Hoop Buildings (H), alphanumeric notation of, 198 Hormel Institute, 6 Hut Buildings (H), alphanumeric notation of, 198 Hysterectomy-derivation, colostrumdeprivation (HDCD), 59 microbes eliminated through, 59 SF, MEW and isowean methods compared to, 62–63 Immunity antigen exposure and, antibodies and, 80 active immunity of piglet and, 80 amino acids and, 81 passive immunity of piglet and, 80, 82 antigen exposure and, vs. performance and management and biosecurity measures and, 88 nervous and immune systems interaction and, 87 nutritional requirements and lean/gain ratio and, 83–85, 85–86 dam immunity status and, 91 defined, 58 emerging infectious diseases and, 91–94 factors of, 64–65, 79 herd immunity and, 90 isowean vs. traditional two-site performance and, 88–89 MEW and isowean pigs exposed to antigens and, 82–83 piglet and sow immunities and, 89–90 summary regarding, 94–95 vaccines and, 79 Incinerator (I), defined, 196 Indirect laboratory test, defined, 184 Infection, defined, 58 Infectious agents. See Microbes Infectious swine diseases control. See specific disease Influenza virus eradication methods compared and, 63 multi-site isowean procedures to eliminate, 75 Inner-sanctum transportation system, 169 Interleukins 1 and 6, 85

211

Index International isowean facilities, 10, 32, 34 in Canada, 22, 28 in Chili, 28, 89 in Europe, 6–7, 206 in Spain, 31 in Switzerland, 74 in the United Kingdom, 6, 52 Isolated weaning, 189 Isolation facilities of, 151 health status of breeding stock in, 183–184 NurFin isolation and, 163–164 procedures of, 163 Isolation for breeding stock (IB), defined, 196 Isowean defined, 189 term usage and, 18, 202 See also Isowean Principle Isowean Principle Actinobacillus pleuropneumoniae eliminated by, 104 atrophic rhinitis eliminated by, 114 defined, 189 infectious agents eliminated by, 33–34, 40, 62, 63–70 Mycoplasma hyopneumoniae eliminated by, 104 performance and, 23–24, 25, 40 procedures of, 61–62, 70–71 PRRSV eliminated by, 109 PRV eliminated by, 111 Serpulina hyodysenteriae eliminated by, 117 Streptococcus suis and, 115 synonyms of, 61 TGE eliminated by, 119 See also Future rearing systems and facilities; Immunity; Microbes; Multi-site isowean production; Multi-site rearing systems; Policy decisions and opportunities Johnson, Rod, 28 Jolly, Robert, 158 Kleen Lean breeding stock company, 6 Laboratory diagnostic testing. See Breeding stock production Lagoon (Lag), defined, 196 Lawsonia intracellulare, Leptospira spp., characteristics of, 66 Lecce, Jim, 207 Leman, Al, 28 Leptospira spp. characteristics of, 66 emergence of, 91, 93 eradication methods compared and, 63

MEW or isowean to eliminate, 70 multi-site factor in emergence of, 93 multi-site isowean procedures to eliminate, 75 risk factors for, 93 vaccination against, 93 Leurs, Dave, 20 Load-in/load-out facilities, 167–169 Load-out (LO), defined, 196 Locus (loci, L) defined, 10, 188, 197 term usage and, 203 Lush, Jay, 178 Lysons, Dick, 15 Management of multi-site rearing systems. See Multi-site rearing systems, management of Marsh, Will, 34, 187 Mausservey, Mireille, 34 McCulley, Bob, 32 Medicated early weaning (MEW), 37 defined, 10–11, 14, 189 disease agents eliminated using, 15–17, 40, 63–70 HDCD, SF and isowean methods compared to, 62–63 as multi-site rearing system, 37 PRRSV eliminated by, 109 SPF pig production through, 61 See also Immunity Medications, immunities and, 65 Menard Farms, 28 MEW. See Medicated early weaning (MEW) Micoplasma hyopneumoniae characteristics of, 67 Pasteurella multocida characteristics and, 67 Microbes age variation in farrowing room and, 65 airborne, aerosol transmission of, 167, 168 antibodies and, 58 carrier state and, 58 defined, 57 disease incubation and, 58 HDCD, SF, MEW and isowean methods compared and, 62–63 infection, defined and, 58 infectious agents eradication, from entire herd and, 74–76 MEW and isowean and, 63–64 biosecurity and, 68 HDCD and SF methods compared to, 62–63 medications and, 65 sanitation and, 65 sow and piglet immunities and, 64–65

212

Index specific agents excluded by, 68–70 weaning age and, 65 multi-site isowean production and, 70–74 MW and isowean and, 65 in newborn piglet and, 59 hysterectomy-derivation and colostrumdeprivation and, 59 isowean and, 61–62 MEW and, 61 origin of, 58–59 normal microbes and, 57–58 pathogen characteristics and, 66–67 snatch farrowing and, 59 summary regarding, 75 See also Immunity; specific disease MMEW. See Modified early weaning (MMEW) Modern-day multi-site production, defined, 13, 193 Modified early weaning (MMEW) isowean synonymous with, 61, 189 as multi-site rearing system, 37 term usage and, 202 See also Isowean Monocytic cells, 85 Moore, Camille, 28 Multiple locus (loci, ML) defined, 10, 188 term usage and, 203 Multiple-source isowean production, 37 Multi-site isowean production 1987-1996, 26–32 breeding stock production and, 181–182, 183 defined, 13, 37, 193 example of, 24 infectious agents eliminated using Actinobacillus pleuropneumoniae, 74–76 efficacy of methods compared, 74–76 from entire herd, 74–76 factors in, 70 procedures by specific system, 71–74 profit figures from, 125–127 term usage and, 203 See also Future rearing systems and facilities; Multi-site rearing systems; Multi-site rearing systems, management of; Policy decisions and opportunities Multi-site pig production defined, 193 term usage and, 203 Multi-site rearing systems continuous vs. all-in/all-out pig flow and, 39–40 defined, 3, 13, 37 disease emergence and, 93

features summarized, 53–55 F10 production and, 53 Isowean Principle and, 40 NurFin isowean production and, 50–51 one-site vs. traditional two-site production and, 37 outdoor isowean production and, 52–53 performance comparisons and, 89 super isowean nurseries and, 53 term usage and, 203 three-site isowean production and, 40–45 vs. three-site production, 20 two-site isowean production and, 45–46 large two-site isowean systems and, 48 two farmstead conversion and, 47–48 two-site isowean on-site production and, 48–49 See also Immunity; Multi-site rearing systems, management of; Policy decisions and opportunities Multi-site rearing systems, management of biosecurity and airborne or aerosol infectious agents transmission and, 167 definition of, 166–167 inter-site transfer of infectious agents and, 172 intra-site transfer of infectious agents and, 171 introduction and removal of pigs and, 170 isolation procedures and, 163 outside the site introduction of infectious agents and, 170 unloading and loading pigs procedures and, 167–169 feeding and, 166 gilt development and acclimatization procedures and, 162 breeder-weaners and, 161 definition of, 160–161 disease status of replacement gilts and, 161 isolation procedures and, 162 NurFin isolation and acclimatization buildings and, 163–164 recipient sow herd, disease status of and, 162 replacement age and, 161 personnel attributes and, 159–160 Pipestone multi-site system and, 159–160 production targets and, 160 summary regarding, 172 technical factors of, 158 throughput and, farrowing and, 165 finisher stage and, 166 NurFin (wean-to-finish) building and, 166 nursery and, 165

213

Index Multi-source of pigs defined, 13, 189 vs. single source, 21–22, 24–25 term usage and, 203 Murphy, Wendell, 25 Murphy Family Farms, 26–27 Mycoplasma hyopneumoniae eradication methods compared and, 63 F10 vs. isowean production and, 53 Glasser’s disease and, 99 MEW or isowean to eliminate, 68 multi-site factor in emergence of, 93 multi-site isowean procedures to eliminate, 72–74, 75 mycoplasmal pneumonia caused by, 100–102 one- and three-site elimination of, 33–34 Plomgaard method to eliminate, 90 Streptococcus suis and, 115 vaccination against, 93 Mycoplasma hyorhinis, rhinitis caused by, 112 Mycoplasmal pneumonia control of, 101–102 diagnosis of, 101 nature of causative agent and disease of, 100 prevention of, 101 transmission and spread of, 100 treatment of, 101 NAHMS (National Animal Health Monitoring System), 5 National Animal Health Monitoring System (NAHMS), 5 National Pork Producers Council (NPPC), 14, 20, 22, 187 National Pork Producers Council Production and Financial Task Force, 8 National Pork Production and Financial Standards Technical Manual (Marsh, ed.), 34, 187, 203 Nervous system, immune system interaction with, 87–88 Newsham Hybrids, 29 Nomenclature for pig production rearing systems, defined, 13, 188 NP. See Number of pigs (NP) NPPC (National Pork Producers Council), 14, 20, 22, 187 NS (number of sows), defined, 195 Number of pigs (NP), defined, 195 Number of sows (NS), defined, 195 NurFin isowean production, 13, 32–33 advantages, disadvantages of, 166 alphanumeric notation and diagrams of, 200 breeding stock production and, 180

description of, 50 infectious agents eliminated in, 71, 73 profit figures regarding, 138 NurFin isowean two-site production, defined, 189 Nursery/finish (NF) building alphanumeric notation of, 198 defined, 13, 190 Nursery (N) production stage, 8 alphanumeric notation of, 198 defined, 10, 188 Nutrition feed intake factors and, 154–155 lean/gain ratio, immunity and, 85–86 lysine requirements and, 86 Office (FF), defined, 195 One-site production (farrow-to-finish). See also Multi-site rearing systems alphanumeric notation and diagram examples of, 199 breeding stock production on, 6–7, 181 defined, 37, 189 expansion of to three-site isowean, 42 profit figures from, 125, 127 On-locus well-separated buildings, alphanumeric notation of, 198 Open front (OF), defined, 196 Oswald Project, 26 Outdoor isowean production, 52–53 alphanumeric notation and diagrams of, 202 defined, 193 infectious agents eliminated in, 71, 73 Parvovirus eradication methods compared and, 63 multi-site isowean procedures to eliminate, 75 Passive immunity, 80 Pasteurella multocida, 17, 112 continuous vs. all-in/all-out pig flow and, 40 eradication methods compared and, 63 MEW or isowean to eliminate, 68 multi-site isowean procedures to eliminate, 72–74, 75 pleuropneumonia caused by, 102 Streptococcus suis and, 115 Pathogens. See also Microbes antibodies and, 58 defined, 57 Patience, John, 18 Performance effect. See also Policy decisions and opportunities vs. antigen exposure, 83–85 explanations of, 18–19 feed intake factors and, 154–155, 166 financial measures of, 128

214

Index lean/gain ratio and, 85–86 measures of, 129 production costs and, 130 PIC (Pig Improvement Company, Ltd.), 6, 14 Pig Improvement Company, Ltd. (PIC), 6, 14 Pipestone multi-site system, 159–160 Pits (P), defined, 196 Pleuropneumonia control of, 103–104 diagnosis of, 103 nature of causative agent and disease of, 102 prevention of, 103 transmission and spread of, 102–103 treatment of, 103 Plomgaard, Jorgan, 33–34 PRRSV and, 105, 109 Plomgaard method, of pathogen elimination of Actinobacillus pleuropneumoniae, 104 Policy decisions and opportunities breeding stock source and genetic potential of, 145 health status of, 142–143, 145 numbers of for large herd, 145–146 replacement of, 146 source of, 145 straight-line distribution and, 145 building design and materials and, 150 all-in/all-out pens, rooms, buildings or loci, 152–153 feeding program, 153–155 isolation and acclimatization facilities, 151–152 load-in/load-out facilities, 151 pig welfare and, 155 sanitation and, 155 disease elimination and, 141–142 food safety and pork quality and, 155 genetics and, 143–144 location issues and, 146–147 multi-site isowean system NurFin isowean production and, 137–138 outdoor isowean production and, 136–137 selection factors in, 131–132 three-site (multi-source, multi-locus production) and, 135–136 three-site (single source, single-loci) production and, 132, 134 two-site isowean and, 136–137 multi-site production systems, production costs and, 130–131 phased construction and, 138–140 pigs per site and expansion issues and, 140–141 production and financial targets and, 128–129

profit figures by production system and, 125–127 rearing system issues and, 147–148 summary regarding, 155–156 transportation issues and, 148–150 Porcine reproductive and respiratory syndrome (PRRS) control of, 108–109 diagnosis of, 105–106 Glasser’s disease and, 99 nature of causative agent and disease of, 104 prevention of through gilt development, 107 through PRRSV-negative replacement gilts, 108 through PRRSV-positive recipient herd, 107 through PRRSV-positive replacement gilts, 107–108 in recipient sow herd, 162 replacement gilts and, 161–162 Streptococcus suis and, 1126 transmission and spread of, 105 treatment of, 106 Porcine reproductive respiratory syndrome (PRRS) virus continuous vs. all-in/all-out flow and, 40 eradication methods compared, 63 MEW or isowean to eliminate, 69 multi-site isowean procedures to eliminate, 72–74, 75 in newborn piglet, 58 Plomgaard method to eliminate, 90 three-site elimination of, 33–34 Porgen Company, 28 Poulin, Marie-Claude, 53 Power ventilation (PV), defined, 196 Pre-nursery (PreN) production stage, 188 alphanumeric notation of, 188 defined, 10 Production, factors of, 158. See also Performance effect Production nucleus (PN), defined, 197 Production pyramids, 177–180 PRRS. See Porcine reproductive respiratory syndrome (PRRS) virus PRV. See Pseudorabies virus (PRV, Aujeszky’s disease) Pseudorabies virus (PRV, Aujeszky’s disease), 7, 41 control of, 111 diagnosis of and vaccination against, 110 eradication methods compared and, 63 isowean to eliminate, 26, 68 MEW to eliminate, 17, 19, 68 multi-site isowean procedures to eliminate, 72–74, 75

215

Index Pseudorabies virus (continued) nature of causative agent and disease of, 109–110 prevention of, 111 three-site production to eliminate, 9–10, 41 transmission and spread of, 110 Pyramid system disease introduction in, 6 origination of, 6 See also Production pyramids Recycled lagoon water (RLW), defined, 196 Return on assets (ROA) financial measures, 128 Return on equity (ROE) financial measures, 128 Rhinitis. See Atrophic rhinitis Roadnight, Richard, 52 Ross, Doug, 59 Rotational-cross breeding system genetic improvement and, 6 introduction of, 177 Salmonella, 206 characteristics of, 67 eradication methods compared and, 63 MEW or isowean to eliminate, 69–70 multi-site isowean procedures to eliminate, 75 Sand, Chuck, 7, 20, 26, 27 Sanitation microbe elimination and, 65 unloading and loading procedures and, 167–169 Schuiteman, Kirk, 53 SDC. See Segregated disease control (SDC) Segregated disease control (SDC) as isowean synonym, 61, 189 as multi-site rearing system, 37 term usage and, 202 See also Isowean Segregated early weaning (SEW). See also Isowean defined, 14 as isowean synonym, 189 term usage and, 202 Segregated weaning, age-segregated rearing (ASR), defined, 189 Sensitivity, of laboratory tests, 183 Serpulina hyodysenteriae eradication methods compared and, 63 multi-site isowean procedures to eliminate, 72–74, 75 Serpulina pilosicoli, 116 Serpulina (Treponema) hyodysenteriae, 116–117 SEW. See Segregated early weaning (SEW) SF. See Snatch farrowing (SF)

Shower (S), defined, 195 Single locus (loci, SL) defined, 10, 188 term usage and, 203 Single-sex feeding (SSF), defined, 195 Single source of pigs defined, 13, 189 term usage and, 203 vs. multi-source of pigs, 21–22, 24–25 Site (S) number defined, 10, 188, 197 term usage and, 203 Snatch farrowing (SF), 59 HDCD, MEW and isowean methods compared to, 62–63 Snyder, Dave, 20 Source of pigs, defined, 13, 188–189 Sow immunities, 89–90 Specificity, of laboratory tests, 183 Specific pathogen-free (SPF), 6–7 concept of, 6–7 HDCD and, 59 primary SPF herds and, 59 SPF. See Specific pathogen-free (SPF) Spirochetal diarrhea. See Swine dysentery and spirochetal diarrhea Spronk, Gordon, 158 SSF. See Single-sex Feeding (SSF) Stages of production (SP), 188, 197 Stahly, Tim, 25–26 Staphylococcus hyicus, 67 Stoecker, Randy, 20, 21 Straight-line distribution, of breeding stock, 145 Streptococcus suis. See also Streptococcus suis type 2 antibodies in colostrum and, 65 characteristics of, 67 control of, 115–116 diagnosis of, 115 MEW or isowean to eliminate, 62, 63, 68 multi-site isowean procedures to eliminate, 72–74, 75 nature of causative agent and disease of, 114–115 prevention of, 115 transmission and spread of, 115 treatment of, 115 Streptococcus suis type 2 emergence of, 91, 93 eradication methods compared and, 63 multi-site factor in emergence of, 93 risk factors for, 93 Super isowean nurseries, 52 Super Pollo, 28, 30 Swine diseases control. See specific disease

216

Index Swine dysentery and spirochetal diarrhea control of, 117 diagnosis of, 116 nature of causative agent and disease of, 116 transmission and spread of, 116 treatment and prevention of, 117 Swine influenza virus vaccination, 93 TGE. See Transmissible gastroenteritis (TGE) virus Thacker, Eileen, 93 T helper cells, 85 Thomas, Steve, 29 Thompson, Bob, 105, 108 Thornton, Keith, 15 Three-site isowean production. See also Multisite rearing systems alphanumeric notation and diagrams of, 200–201 defined, 192–193 infectious agents eliminated in, 71, 72 vs. multi-site pig production, 20 multi-source, multi-loci, disadvantages of, 43–44 performance in, 46 phased construction of, 138–140 profit figures from, 125–127 term usage and, 202–203 Throughput breeding and gestation and, 164–165 definition of, 164 farrowing and, 165 finisher and, 166 NurFin (wean-to-finish) building and, 166 nursery and, 165 Thymus glands, 84–85, 87 Tissue necrosis factor (TNF), 85 Titer, defined, 184 T lymphocytes, 85, 87 TNF (tissue necrosis factor), 85 Traditional two-site production. See also Multisite rearing systems; Two-site isowean production alphanumeric notation and diagrams of, 199 breeding stock production on, 6–7 defined, 6, 189 as multi-site rearing system, 37, 42–43 vs. isowean, immune performance and, 88–89 Transmissible gastroenteritis (TGE) virus characteristics of, 67

control of, 119 diagnosis of, 118–119 herd immunity to, 90 multi-site isowean procedures to eliminate, 72–74, 75 prevention of, 119 transmission and spread of, 118 Transport vehicles, 148–150 Trettin, Harold, 27 Trichina spiralis, 206 Tubbs, Rick, 105, 108 Two-farmstead conversion, 47–48 Two-site isowean on-site production, defined, 190, 192 Two-site isowean production. See also Multisite rearing systems; Traditional two-site production alphanumeric notation and diagrams of, 199 breeding stock production and, 181 cost reduction and, 48 defined, 12, 189 infectious agents eliminated in, 71, 73 types of, 189–190 Underdahl, Norman, 6 Vaccination diseases used against, 93 immunity and, 79, 91 against pseudorabies virus, 110–111 against Streptococcus suis, 115 WA. See Weaning age (WA) Waste-store aboveground (WSAG), defined, 196 Water supply (WS), defined, 196 Weaning age (WA) defined, 195 determination of, 165 emerging diseases and, 91–92 immunity and, 64, 65, 66–67, 79 Wean-to-finish, defined, 13, 32–33, 190 Williams, Noel, 25–26 Wilson, Eldon, 16, 18, 20 Wiseman, Barry, 16, 19, 20, 22, 26 Woolley, Ken, 14, 15, 19, 20, 26, 28, 177 Young, George, 6 Zoonotic agents, 170

217