Understanding animal breeding

518 Pages·2014·14.705 MB·English

by  Bourdon, Richard M.

Pearson New International Edition

Understanding Animal Breeding

Richard M. Bourdon
Second Edition
International_PCL_TP.indd 1 7/29/13 11:23 AM
ISBN 10: 1-292-04003-3
ISBN 13: 978-1-292-04003-5
Pearson Education Limited
Edinburgh Gate
Harlow
Essex CM20 2JE
England and Associated Companies throughout the world
Visit us on the World Wide Web at: www.pearsoned.co.uk
© Pearson Education Limited 2014
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the
prior written permission of the publisher or a licence permitting restricted copying in the United Kingdom
issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC1N 8TS.
All trademarks used herein are the property of their respective owners. The use of any trademark
in this text does not vest in the author or publisher any trademark ownership rights in such
trademarks, nor does the use of such trademarks imply any affi liation with or endorsement of this
book by such owners.
ISBN 10: 1-292-04003-3
ISBN 10: 1-269-37450-8
ISBN 13: 978-1-292-04003-5
ISBN 13: 978-1-269-37450-7
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library
Printed in the United States of America
Copyright_Pg_7_24.indd 1 7/29/13 11:28 AM
11123367880261576751570513
P E A R S O N C U S T O M L I B R AR Y
Table of Contents
Preface, Acknowledgements
Richard M. Bourdon 1
Part I. Animal Breeding from the Top Down
Richard M. Bourdon 5
Chapter 1. What is the "Best" Animal?
Richard M. Bourdon 7
Chapter 2. How are Animal Populations Improved?
Richard M. Bourdon 21
Part II. Animal Breeding from the Bottom Up
Richard M. Bourdon 35
Chapter 3. Mendelian Inheritance
Richard M. Bourdon 37
Chapter 4. Genes in Populations
Richard M. Bourdon 60
Chapter 5. Simply-Inherited and Polygenic Traits
Richard M. Bourdon 75
Part III. Selection
Richard M. Bourdon 81
Chapter 6. Selection for Simply-Inherited Traits
Richard M. Bourdon 83
Chapter 7. The Genetic Model for Quantitative Traits
Richard M. Bourdon 106
Chapter 8. Statistics and Their Application to Quantitative Traits
Richard M. Bourdon 127
Chapter 9. Heritability and Repeatability
Richard M. Bourdon 165
I
222223333334444503679112379334512129879975735791
Chapter 10. Factors Affecting the Rate of Genetic Change
Richard M. Bourdon 202
Chapter 11. Genetic Prediction
Richard M. Bourdon 231
Chapter 12. Large-Scale Genetic Evaluation
Richard M. Bourdon 262
Chapter 13. Correlated Response to Selection
Richard M. Bourdon 279
Chapter 14. Multiple-Trait Selection
Richard M. Bourdon 298
Part IV. Mating Systems
Richard M. Bourdon 317
Chapter 15. Selection for Simply-Inherited Traits
Richard M. Bourdon 319
Chapter 16. Mating Strategies Based on Animal Performance: Random
Richard M. Bourdon 329
Chapter 17. Mating Strategbies Based on Pedigree Relationship: Inbreeding and Outbreeding
Richard M. Bourdon 337
Chapter 18. Hybrid Vigor
Richard M. Bourdon 375
Chapter 19. Crossbreeding Systems
Richard M. Bourdon 397
Part V. New Techniques, Old Strategies
Richard M. Bourdon 433
Glossary
Richard M. Bourdon 435
Appendix
Richard M. Bourdon 447
Answers to Odd-Numbered Problems
Richard M. Bourdon 459
Index 511
II
Preface
My goal in assembling the second edition of Understanding Animal Breeding,as in
writing the original, was to create a text that is thorough yet unintimidating. I
wanted to take the theoretical, often mathematical concepts of animal breeding,
concepts such as breeding value and heritability, and make them palatable to read-
ers who are new to the subject and who might not ordinarily be comfortable with
abstractions of this kind. Understanding Animal Breedingis a textbook, but I hope
it does not feellike a textbook. It is a learning text, not simply a reference book. It is
designed not just to present information, but to teach how that information is best
perceived (and, in some cases, how it should notbe perceived).
Understanding Animal Breedingis really two books in one. The main body of
the text contains a minimum of mathematics and is designed for all readers, but es-
pecially for those who are put off by equations and Greek symbols. (It is not, how-
ever, completelyequation or symbol free.) For those (like me) who feel more com-
fortable with a concept if they can see it demonstrated or proven mathematically, I
have provided a more mathematical treatment in boxed sections which appear in
most chapters. To make sure that the book could be read without the mathemati-
cal sections and still make sense, I wrote the entire non-mathematical text before
adding in the math sections.
There are at least three ways to read this book. If you are interested only in
the concepts and would rather avoid math, skip the boxed sections. If math is sec-
ond nature to you, read the text straight through without skipping. For most peo-
ple, the most productive way to read the book may be to combine these ap-
proaches. At any one sitting, read the non-mathematical text first. When the
concepts seem reasonably clear, go back and study the math behind them.
Like so many technical subjects, animal breeding has its own language, jar-
gon to some, essential terms to others. To help you understand the language, I have
highlighted key words and phrases in bold print in the text and defined them in
the margins. The definitions reappear in the glossary. If you are using this book in
a course in animal breeding, a part of studying should involve revisiting the defi-
nitions. Simply knowing definitions is not equivalent to understanding a subject,
but notknowing them is a sure sign that your understanding is less than complete.
Aword of caution about definitions: In writing and revising this book, I learned
that animal breeding terms, like words in general, take on different meanings in
From Understanding Animal Breeding, Second Edition. Richard M. Bourdon.
Copyright © 2000 by Pearson Education, Inc. All rights reserved.
1
xviii Preface
different times and different contexts. Sometimes this results from sloppy usage—I
am as guilty as anyone—and sometimes it reflects a justifiable shift in meaning. In
cases where a change in meaning seemed more to contaminate a good concept than
improve it, I stuck closely to the original definition. In other cases, I adopted the
change in meaning, sometimes providing more than one definition. I have paid lit-
tle attention to or omitted altogether a few animal breeding terms that I felt, for one
reason or another, ought to be put out of their misery, and have gone so far as to in-
vent some terms that I thought needed inventing.
The exercises at the end of each chapter are designed to reinforce understand-
ing of the concepts presented in the text. The exercises are of two kinds: study ques-
tions and problems. The study questions provide a way for you to test your com-
prehension of the general concepts presented in each chapter. The problems tend to
be mathematical in nature and often require that you read the boxed sections of the
book in order to solve them. I make no claim for the practicality of the problems.
They do not represent a sample of the tasks that a real-life animal breeder would en-
counter every day. Some are downright silly. Yet they can be very revealing. Fully
worked out answers to odd-numbered problems appear in the Appendix.
Traditionally, textbooks begin with the most basic theoretical concepts, then
build on them in a step by step fashion until at some point application becomes ap-
parent. I have chosen to reverse this approach. I prefer to stress application first,
then explain the theory needed to answer applied questions. In this way the the-
ory becomes more meaningful because its usefulness is already evident. I have not
been entirely consistent in presenting application before theory in this book—that
is not always possible—but you may notice that many concepts do not appear un-
til they are truly needed.
I have also tried to present the big picture before the details. Part 1 is entitled
Animal Breeding from the Top Down.It examines the fundamental questions faced by
animal breeders and explains in a very general way the tools used to answer those
questions. Only after animal breeding has been viewed from this very broad per-
spective does Part 2: Animal Breeding from the Bottom Up review the essentials of
classical genetics. The next two sections describe the basic tools of animal breed-
ing, selection and mating, in more detail. Part 5: New Techniques, Old Strategiescon-
tains two rather different chapters: one on the potential effects of biotechnology on
animal breeding and one containing practical advice for breeders. This last chap-
ter is completely applied in nature, although it assumes knowledge of the theoret-
ical concepts presented earlier. It serves to tie things together.
Despite all the emphasis on application, Understanding Animal Breedingis
nota text on applied animal breeding. It is a book about underlying principles. You
can learn from it the precise meaning of an expected progeny difference, but do not
expect it to explain what to look for in a herd sire.
As a book on animal breeding in general, Understanding Animal Breeding
should be applicable to any domestic species, and I have attempted to use many
different species in the examples. But I must admit to beef cattle experience and
bias. I tend to emphasize the animal breeding technology (EPDs, etc.) found in cat-
tle breeding, which just happens to be the most advanced technology around. This
may be frustrating for some, especially for those whose interests are in recreational
or companion animals. To a dog breeder, for example, an EPD, if it is not mistaken
for a social disease, is a thing of fiction. What is important to remember, however,
is that the underlying principles of animal breeding are the same for all species;
only breeding technologies differ.
2
Preface xix
ACKNOWLEDGMENTS
I am indebted to everyone who reviewed the first edition of Understanding Animal
Breeding.In particular, I wish to acknowledge those who assisted as reviewers in
preparation for this new edition: Melinda J. Burrill, California State Polytechnic
University–Pomona; Joe Gotti, Stephen F. Austin State University; Carl L. Hausler,
Southern Illinois University; Don D. Kress, Montana State University; William Lam-
berson, University of Missouri; Steven D. Lukefahr, Texas A & M University–
Kingsville; and David L. Thomas, University of Wisconsin–Madison. Their com-
ments were thoughtful and helpful, and while I could not accommodate all their
suggestions—some would have changed the essential nature of the book and put
me in the awkward position of explaining subjects I know little about—I tried to ad-
dress their main concerns. I am also thankful for the many informal comments I re-
ceived over the past two years, mostly from animal breeding instructors. With their
help I compiled a surprisingly long list of first-edition errors. The second edition un-
doubtedly contains mistakes, but they should be relatively few. Special thanks to
those who responded to my e-mail queries about areas I was unsure of. In some
cases, they gave me confidence in my own understanding; in others, they straight-
ened me out. Anumber of individuals and organizations contributed photographs
and illustrations to this edition. I am thankful for these, as they will add interest to
the book.
I want to thank my colleagues and students at Colorado State University for
their understanding. My regular disappearance to the library to work on the book
has not made me the most accessible professor. I also want to thank all those at Pren-
tice Hall for being patient with me. Everything I do seems to take longer than I plan,
and my particular view of the concept of deadline must have been frustrating.
R.M.B.
Fort Collins, Colorado
3
This page intentionally left blank
I
PART
Animal Breeding
from the Top Down
T
here are two fundamental questions faced by animal breeders. The first asks, What
is the “best” animal? Is the best Labrador retriever the one with show-winning confor-
mation or the one with exceptional retrieving instinct? Is the best dairy cow the one
that gives the most milk; the one with the best feet, legs, and udder support; or the one
that combines performance in these traits in some optimal way? These are matters of
intense debate among breeders, and, in truth, no one has all the answers. The question
is an important one, however, because the answers that breeders decide upon determine
the direction of genetic change for breeding operations, breeds, and even species.
The second question asks, How do you breed animals so that their descendants
will be, if not “best,” at least better than today’s animals? In other words, how are ani-
mal populations improved genetically? This question involves genetic principles and
animal breeding technology, and is the subject of most of this book.
The next two chapters examine these questions from a broad perspective. After
reading them, you should have a good feel for what animal breeding is all about.
From Part I of Understanding Animal Breeding, Second Edition. Richard M. Bourdon.
Copyright © 2000 by Pearson Education, Inc. All rights reserved.
5