Control of Canine Genetic Diseases

George A. Padgett

Description

If you breed dogs for any reason, you must own this book. Genetic diseases are among the most serious hazards on the landscape of modern dog breeding and one of the most vexing challenges facing today's dog breeders. Is it appropriate to open the gene pool to unwanted conditions in the pursuit of physical perfection, or must breeding to the Standard take a back seat to producing healthy animals?

In Control of Canine Genetic Diseases, renowned authority George A. Padgett, DVM, provides an expert road map to help dog breeders everywhere avoid the pitfalls they are almost destined to encounter. For anyone whose goal is to produce healthy, functional and beautiful dogs, this is the book they need. Dr. Padgett provides clear explanations of modes of inheritance, how to conduct and analyze test matings and how to lower the chances of producing affected animals. Numerous tables, diagrams and graphs further enhance the text to facilitate the breeder's understanding.
A Howell Dog Book of Distinction
The Author.

Chapter 1: Introduction.

Chapter 2: Background.

Chapter 3: The Development of Pedigrees.

Chapter 4: Modes of Inheritance.

Chapter 5: Tables and Probabilities.

Chapter 6: The Interpretation and Use of Pedigrees to Determine the Genetic Status of Given Dogs.

Chapter 7: The Interpretation and Use of Pedigrees to Determine the Probable Mode of Inheritance of a Trait.

Chapter 8: Test-Mating.

Chapter 9: Registries and Prioritizing Genetic Diseases.

Chapter 10: Breed Clubs and Control of Genetic Disease.

Chapter 11: For the Breeder.

Appendix 1: Genetic Disease Predisposition by Breed.

Appendix 2: Brief Definitions of Canine Genetic Disorders with Affected Breeds.

References.

Index.

Sujets

• Breeds
• Pets
• Dogs

Informations

• Publié par: Turner Publishing Company
• Date de parution: 05 mai 2008
• Nombre de lectures: 0
• EAN13: 9780470369920
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Control of Canine Genetic Diseases
Control of Canine Genetic Diseases
George A. Padgett, DVM
Professor of Pathology Michigan State University
Howell Book House A Simon & Schuster Macmillan Company 1633 Broadway New York, NY 10019
Copyright © 1998 by George A. Padgett
All rights reserved. No part of this book shall be reproduced, stored in a retrieval system or transmitted by any means, electronic, mechanical, photocopying, recording or otherwise without written permission from the publisher. No patent liability is assumed with respect to the use of the information contained herein. Although every precaution has been taken in preparation of this book, the publisher and author assume no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the information herein. For information, address Howell Book House, 1633 Broadway, 7th floor, New York, NY 10019-6785.
MACMILLAN is a registered trademark of Macmillan, Inc.
Cataloging-in-Publication Data is available upon request from the Library of Congress.
ISBN: 0-87605-004-6
00 99 98 9 8 7 6 5 4 3 2 1
Book design: A&D Howell Design Cover design: Paul Costello
Table of Contents
The Author
Chapter 1 Introduction
Chapter 2 Background
Chapter 3 The Development of Pedigrees
Chapter 4 Modes of Inheritance
Chapter 5 Tables and Probabilities
Chapter 6 The Interpretation and Use of Pedigrees to Determine the Genetic Status of Given Dogs
Chapter 7 The Interpretation and Use of Pedigrees to Determine the Probable Mode of Inheritance of a Trait
Chapter 8 Test-Mating
Chapter 9 Registries and Prioritizing Genetic Diseases
Chapter 10 Breed Clubs and Control of Genetic Disease
Chapter 11 For the Breeder
Appendix 1 Genetic Disease Predisposition by Breed
Appendix 2 Brief Definitions of Canine Genetic Disorders with Affected Breeds
References
Index
The Author
Dr. George A. Padgett received his B.S. in 1959 and both his M.S. and D.V.M. degrees in 1961, all from Michigan State University. He went on to complete four years of postdoctoral work at Washington State University and spent a year as a guest investigator at Rockefeller University in New York City. He was on the faculty at Washington State University from 1965 to 1977 and on the faculty in Veterinary Pathology at Michigan State University from 1977 to the present.
Dr. Padgett has published more than 200 scientific papers and about the same number of papers in various lay publications. He has been the principal investigator or co-investigator on $15 million worth of research, training and construction grants funded by the National Institutes of Health, among other well-known organizations. Widely known in the dog fancy, he has presented seminars for ninety-three national breed clubs in the United States and Canada; he has also been a speaker on canine genetic diseases and for more than 100 other regional specialty and all-breed dog clubs.
He has been the principal author or co-author of several definitive publications that have established the mode of inheritance for thirty-two canine genetic diseases.
In 1997, Dr. Padgett was the recipient of the Eukanuba Canine Health Award for the best article on canine health as determined by the Dog Writers Association of America.
His major research interest is the subject of this book: the control of canine ge-netic diseases.
Dedication
To:
Debra Huggler, Kelly Watson, Patricia Thomas, the late Charlene Wellman, and Rebecca Ammon, all of whom helped me with the footwork or proofing of this book.
The ladies in the word processing center of the Veterinary Clinic, Kathy Winsky, Karen Schiffer, Martha Devlin, and Toni Tenlen, who produced this manuscript, especially Kathy, whose expertise accounted for most of the wonderful pedigrees in this book. They not only typed the book, they kept my grammar and sentence structure reasonably functional throughout the process.
My very special thanks to Kyle Walsh and her son Joshua, who turned the work into fun and without whose help I may not have completed the book in a timely fashion.
CHAPTER 1
Introduction
Genetic diseases in dogs have been with us for a long time. In fact, they probably started when dogs evolved many millennia ago. Because dogs are biologic mechanisms, as are people and all other living things, they are subject to mutations. As a general rule, mutations are negative; that is, they tend to alter some characteristics of the dog that make the animal less able to weather variations in the environment. Some mutations occur in various tissues of the body but do not involve the reproductive cells. We call these somatic mutations. They may do harm to the body—for instance, cause a cancer to develop—but are not passed to the next generation. We will not concern ourselves with mutations of this type.
In this book, we will concern ourselves with those traits that are passed to the offspring via the gametes —the sperm and the ovum. These are the traits that are a boon to the breeder if they are desirable and the bane of the breeder if they are detrimental. While in general, mutations are harmful, they are clearly not all harmful. Some mutations, we select for. While we do not know for certain what type of coat the original dog had, we now know there are many variations available genetically, such as wavy, curly, wiry, long, short and even no coat, as we see in the Chinese Crested (desirable) and in bald Beagles (undesirable). Some of these coat variations we use as a basis for a breed, such as German Wirehaired Pointers or Curly-Coated Retrievers, although they are not the only basis for these breeds. No matter what we think about coats in general, we know the original dogs could not have had all these variations. So over the years, mutations occurred in the coat genes causing the variations that we see. Breeders then selected for coat types they liked and stabilized them by inbreeding to form the more or less uniform coats we see on each breed today. The same things happened with eye color, ear type, coat color, height, weight and all the other characteristics that allow us to distinguish one breed from another and that distinguish each breed from the original dog, however the original dog may have looked. In other words, these are collections of beneficial mutations that breeders put together and stabilized to form the 400 or 500 distinct breeds known in the world today.
A given mutation may be highly prized in one breed and universally considered a horror in the next. Take, for example, the screw-tailed breeds like the Bulldog or the Boston Terrier. The screw tail is caused by an alteration in the vertebral body of the tail vertebra called hemivertebra that allows the tail to twist, and it is desirable in these instances. If a dog of one of these breeds had a straight tail, it would probably be laughed out of the show ring. On the other hand, if a dog of a straight-tailed breed like a Pointer or a Dachshund had a crook in its tail (and it didn’t get stepped on or slammed in a screen door), it would most likely be due to the same trait—hemivertebra. In this case, the kinked tail is frowned upon but is really no detriment to the wellbeing of the dog; however, it has the potential to wreak havoc in the show ring. If the same trait, hemivertebra, occurs in the cervical, thoracic or lumbar spine, it can cause serious harm to the dog and may result in severe pain or posterior paralysis and may be severe enough to require euthanasia of the affected animal. The same trait can be good, so-so, or bad, depending on the breed and the circumstances. In each case, it is genetic, so how we view a trait is very important when we make a decision as to whether or not we are going to concern ourselves about it. This will be a thesis throughout this text; as you will see, you will have to make decisions about what to work on and what to put aside, at least for the moment.
The thrust of this book is the control of canine genetic diseases by breeders and breed clubs. But one of the first things a breeder asks when confronted with a defect that apparently appears suddenly among the progeny they produce is “Is this disorder genetic?”
Sometimes it is easy to tell whether a condition is genetic, but at other times, especially if there are only one or two cases, it is very difficult to determine whether it is or not, and in the final analysis, you may not be able to state with certainty that a trait is genetic in origin.
For traits that repeatedly occur within a breed, the first question to ask is “Is it familial?” While there are many situations in which a disorder occurs in multiple members of a litter, in most instances, the disorder will not recur in spaced litters unless it is genetic. Genetic traits must follow family lines, and they do occur in multiple, widely-spaced litters.
So if a defect occurs among the dogs in your kennel or in your breeding line, you must be sure the diagnosis is accurate. If it is, there are questions you can ask to determine whether a trait is likely to be inherited
a. In your breed
b. In other breeds
c. In other species
If the defect is inherited in dogs or in other species, then the chances that it is inherited in the affected dog(s) in your kennel are good. There are, of course, phenocopies —traits that are known to be genetic, but that can also be produced by something in the environment—that tend to confuse the situation. Cleft palate, a defect that occurs in nearly all breeds of dogs, is an example of a trait in which phenocopies occur. There are twenty-two compounds known to cause cleft palate in dogs. One of these is vitamin A. However, for vitamin A to cause cleft palate, a bitch would have to consume or receive 100,000 units of the vitamin on days 18 through 21 of her pregnancy (the critical period for cleft palate in dogs). That means the bitch would have to have access to the full-strength vitamin A additive o