TITLES OF RELATED INTEREST ANDERSON: Nutrition & Behavior in Dogs & Cats EDNEY: Dog & Cat Nutrition LANE: Jones' Animal Nursing, 4th Edition ROBINSON: Genetics for Dog Breeders GENETICS FOR CAT BREEDERS BY ROY ROBINSON, F.I.Biol. Second Edition PERGAMON PRESS OXFORD · NEW YORK · BEIJING · FRANKFURT SΔO PAULO · SYDNEY · TOKYO · TORONTO U.K. Pergamon Press, Headington Hill Hall, Oxford OX3 OBW, England U.S.A. Pergamon Press, Maxwell House, Fairview Park, Elmsford, New York 10523, U.S.A. PEOPLE'S REPUBLIC Pergamon Press, Qianmen Hotel, Beijing, OF CHINA People's Republic of China FEDERAL REPUBLIC Pergamon Press, Hammerweg 6, OF GERMANY D-6242 Kronberg, Federal Republic of Germany BRAZIL Pergamon Editora, Rua Eqa de Queiros, 346, CEP 04011, Sao Paulo, Brazil AUSTRALIA Pergamon Press Australia, P.O. Box 544, Potts Point, N.S.W. 2011, Australia JAPAN Pergamon Press, 8th Floor, Matsuoka Central Building, 1-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160, Japan CANADA Pergamon Press Canada, Suite 104, 150 Consumers Road, Willowdale, Ontario M2J 1P9, Canada Copyright © 1977 Pergamon Press Ltd. 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, electrostatic, magnetic tape, mechanical, photocopying, recording or otherwise, without permission in writing from the publishers. First edition 1971 Reprinted 1973, 1975 Second edition 1977 Reprinted 1978, 1983, 1987 Library of Congress Cataloging in Publication Data Robinson, Roy Genetics for cat breeders, 2nd edition Bibliography: p. Includes index 1. Cats—Breeding. 2. Cats—Genetics I. Title SF447.5.R6 1977 636.8Ό8'21 77-120591 ISBN 0-08-021209-3 Printed in Great Britain by A. Wheaton & Co. Ltd., Exeter PREFACE THE writing of this book springs from the beUef that the continued advancement of cat breeding rehes upon an acknowledgement of modern trends in animal breeding. It should be recognized that the world of small animal breeding is discarding "rule of thumb" methods for a more balanced programme of scientific method and skilful breeding. The science of genetics has much to offer both to the theory and the practice of cat breeding. The thoughtful breeder should ponder on the fact that once his or her cats are provided with a good home, properly fed and receiving expert veterinary care, the sole hope of producing the superlative animal lies in the art of breeding. In the preliminary chapters an endeavour is made to outline the ele­ mentary principles of heredity. The theory has been subdued to a large extent in deference to the more practical considerations. Quite consider­ able advances have been achieved in the practical application of genetics to the larger, economically regarded, livestock and these techniques may, with profit, be adapted to cat breeding. The cat may be thought of as "different", especially in its psychological make-up, but its heredity differs little from other animals. An account of proven heredity of the cat is of considerable interest in itself, and of immense value for the complete understanding of the animal. A fair amount of information on the genetics of the cat has been published, in the main, in relatively inaccessible scientific journals. A simplified summary of this work is given with special regard to the constitution of breeds which, so far as the author is aware, has not previ­ ously been attempted in a comprehensive manner. Research into feline genetics has been carried out in many diflferent countries, for the cat is truly cosmopolitan, and the benefits to be derived are similarly univer­ sal. It is hoped that this book will be of service to breeders wheresoever in the world they may reside. A special chapter is given on those abnormalities which are either suspected or known to be genetically determined. Some abnormalities Viii PREFACE are due entirely to genetic causes and some result from a genetically determined constitution interacting with a dietary deficiency or develop­ mental defect which would not necessarily upset a normal cat. It is hoped that this chapter will be of service to veterinary surgeons in the pursuit of their profession. I am indebted to the many breeders who have discussed various problems with me and for their interest. Discussions with Alison Ashford, Peter Dyte, Roy and Maureen Silson and Patricia Turner, knowledgeable breeders all, have been particularly valuable. My thanks are due to Animal Photography Ltd., Anne Cumbers, Cat Information Centre, Will Green and Hugh Smith for permission to reproduce pho­ tographs. ROY ROBINSON PREFACE TO SECOND EDITION The last 5 years have seen a remarkable upsurge of interest in cat genetics and a corresponding increase in our knowledge. This is most heartening, although one must acknowledge that certain problems still remain unsolved and new ones have arisen. However, that's animal breeding! The incorporation of new information has meant that the text of the first edition has had to be carefully revised. In particular. Chapters V and VII have been expanded and Chapter VI rewritten in its entirety. I am indebted to many cat fanciers and especially to Miss Patricia Turner for fruitful discussions. ROY ROBINSON Viii PREFACE are due entirely to genetic causes and some result from a genetically determined constitution interacting with a dietary deficiency or develop­ mental defect which would not necessarily upset a normal cat. It is hoped that this chapter will be of service to veterinary surgeons in the pursuit of their profession. I am indebted to the many breeders who have discussed various problems with me and for their interest. Discussions with Alison Ashford, Peter Dyte, Roy and Maureen Silson and Patricia Turner, knowledgeable breeders all, have been particularly valuable. My thanks are due to Animal Photography Ltd., Anne Cumbers, Cat Information Centre, Will Green and Hugh Smith for permission to reproduce pho­ tographs. ROY ROBINSON PREFACE TO SECOND EDITION The last 5 years have seen a remarkable upsurge of interest in cat genetics and a corresponding increase in our knowledge. This is most heartening, although one must acknowledge that certain problems still remain unsolved and new ones have arisen. However, that's animal breeding! The incorporation of new information has meant that the text of the first edition has had to be carefully revised. In particular. Chapters V and VII have been expanded and Chapter VI rewritten in its entirety. I am indebted to many cat fanciers and especially to Miss Patricia Turner for fruitful discussions. ROY ROBINSON I. INTRODUCTION A FEW words may not be out of place on the sort of information a cat breeder might be expected to obtain from genetics. Three aspects will probably be of special interest. Firstly, there is genetics itself, especially that part of it which is concerned with coat colour in mammals. No breeder should confine himself to cats alone in his reading. Studies on variation in other species of animals could give valuable insight into similar variation in cats. This is an aspect which makes Searle's (1968) interesting book on colour variation so useful, dealing as it does with the whole spectrum of mammalian species. Secondly, a detailed account of the known genetics of the cat. The various mutant genes which have been reported and the effects they produce. The variation of colour and coat types which result from combi­ nations of the genes. How these have been seized upon by breeders and skilfully woven into established breeds. An account of variation both within and outside the breeds which is of intrinsic interest and which might be useful for creating new breeds. All of these aspects will be discussed in succeeding sections. Some can be covered in depth but others can only be lightly touched upon because of sketchy information or lack of reliable knowledge. Finally, there are the methods of animal improvement which could be used in cat breeding. What constitutes inbreeding and if or when to employ it. What is selection, when to apply it and which traits should be concentrated upon. A discussion of these problems is undoubtedly called for and should be satisfied. In dealing with methods of animal im­ provement, it is rarely possible to go beyond a general discussion becauSe only the breeder has the data from which to make correct judgements. In a sense, animal improvement at an elementary level remains an art rather than an exact science. It is a question of gauging the worth of the individual by inspection, rather than by measurement, and of making decisions based on shrewd judgement, rather than on a set number of matings or on the passage of a certain number of generations. 2 GENETICS FOR CAT BREEDERS When all has been said and done, the occasion may arise when certain observations appear "odd" and do not fit into the scheme of things. One possibility which should be looked into at the onset is that a mistake has not been made. A mistaken identification, an error in the breeding records or an accidental mis-mating. Only saints are perfect—the rest of us make all sorts of errors. If mistakes can be ruled out, then it may be that the genetic explanation is not as accurate or as complete as it could be. Alternatively, something new has been discovered, such as the discovery of two genes for rex coat of some years back or the folded eared mutant of recent years. In this event, it is wise to seek competent advice. Whenever unexpected results occur, it is always advisable to consult other people. The chances of discovering something novel are slim but the possibility is always there. Mendelism and Genetics The first accurate description of the principles of heredity was enunciat­ ed in 1866 by Gregor Mendel. Alas for the inspired reasoning of this remarkable man, the scientific climate was not ripe for ready acceptance of his simple, almost blunt, account and Mendel's discovery languished until 1900. Round about this time, the prevailing ideas on heredity and evolution were being critically appraised by inquiring minds and, in particular, biology was beginning to emerge as an experimental, as opposed to an observational, science. About 1900, Mendel's work was acclaimed by three biologists, independently and more or less simulta­ neously. This fact should demonstrate perhaps more than any other how biological thought had changed in the intervening 34 years. It is common knowledge that Mendel carried out his experiments with the ordinary garden pea. Once the basic principles were grasped, there were many people who were eager to discover if his ideas applied to other plants and to animals. It was soon found that they did, in most cases with astonishing similarity and, in others, with subtle variations which served to strengthen and to extend the principles he had formul­ ated. Mendel's laws of heredity, as his principles are known, stood up to the test of repeatable experiment. Their generality for all species of plants and animals implied that they were fundamental. In the early days, the study of heredity was known as "Mendelism" until W. Bateson INTRODUCTION 3 in 1906 coined the word "genetics" for the new biological discipline. Thus, heredity became a science, with principles which can be checked and with laws of real predictive value. From the humble beginning of a man pottering around in a spare corner of his garden, genetics has grown to such an extent that research establishments are devoted to the subject and no corner of biology or medicine can escape its impact. For those who find pleasure in learning a subject by reading of its historical develop­ ment, Dunn's (1965) book is recommended. There is no grand design in science. This means that the growth of fundamental ideas and their application can be very uneven. In some respects, genetics has had more than its fair share of opposition from established practice. Possibly this is understandable since heredity has often been thought of as something intangible and difficult to pin down. Thus, it became shrouded in mystery and bedeviled with mystical ideas. Unfortunately, animal breeding has a very rich quota of legend based on all sorts of queer prejudices. This has delayed the practical application of genetics to some forms of animal breeding; particularly, it would seem, in those branches less exposed to economic pressures. However, there are encouragmg signs of increasing awareness that genetics has something worthwhile to offer the person who is willing to make the effort. It required several decades for the foundations of genetics to be laid. In the meantime, animal breeding carried on more or less as usual. There was indeed more emphasis placed on selection but this was merely an intensification of current practice. That selection was the key to animal breeding had been known since Darwin focused attention upon how eflTective the process can be. On the other hand, a rational genetic theory of animal improvement had to wait upon an understanding of the effects of inbreeding, cross-breeding and the relative effectiveness of various methods of selection. The work of Lush (1945) is monumental in this respect. There is now a very considerable and impressive amount of theoretical and experience on the genetic aspects of animal improve­ ment. Once the mechanism of heredity had been satisfactorily settled, it became obvious that concepts based on the "percentage of blood" and the overestimated influence of remote ancestors had to be revised. Even the use of pedigrees in breeding became suspect unless one is very fami­ liar with the ancestors listed and could recall their apparent worth. A tabu­ lation of names, devoid of accurate description, is scarcely any value at GENETICS FOR CAT BREEDERS all except for intimating that the individual is derived from a well-known stock. If the ancestors have high-sounding names, but are unknown: how can the worth of the animal or its potential breeding be assessed? Nomenclature The domestic cat is often referred to as Felis domesticus. The word Felis indicating that the animal belongs to the main genus of cats and the word domesticus indicating that it is a domesticated form. This is fair enough. However, Carl Linne, the founder of scientific classification, named the domestic cat as Felis catus. This designation is also often employed. Everything would still be straightforward but for the fact that Linne singled out the blotched type of tabby as catus, apparently neglectful or oblivious to the equally common mackerel type. In some people's eyes, this omission needed rectifying, so the mackerel has come to receive the designation of torquata. The name of domesticus is seemingly the most appropriate even if, in strict nomenclative terms, it is not correct. As a designation, it certainly describes the present status of the cat. It is unfortunate that the origin of the cat is so obscure, for the animal must obviously be a domesticated form of a wild species. If the wild ancestor was definitely known, the use of the species may seem preferable, even if domesticus is added. However, at present, the presumptive wild ancestor is not known with certainty although there seems to be excellent grounds for suggesting that it belongs to the silvestris-lybica species complex. The typical tabby pattern of these species is the mackerel type. For this reason it is customary to refer to the mackerel form as the "wild type", from which the blotched sprang as a mutant. Origin and Species Hybridity Few writers on the domestic cat can resist speculation on the origin of the animal. It is well known that the ancient Egyptians revered the cat and worshipped a cat-goddess. Egypt is commonly regarded as being a major centre of origin but whether it is the only centre is perhaps open to question. There is nothing to prevent anyone attempting to domesti­ cate the cat anywhere and at different times. Certain Asiatic peoples may have had a hand in the domestication. It is doubtful if the problem will