1 Governing Council of the Cat Fancy Gccf Policy On
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GOVERNING COUNCIL OF THE CAT FANCY GCCF POLICY ON THE USE OF OUTCR OSSING IN CAT BREEDI NG PROGRAMMES 1 Introduction by Professor Leslie A. Lyons, PhD – University of Missouri, Columbia, MO USA A breed is defined as a group of animals related by descent fro m common ancestors that are visibly similar in most characters. Breeds generally refer to a distinct group of domesticated animals that are different from the wild type, are under the influence of man, and are incapable of maintaining their distinctive qua lities in nature. Most cat breeds do fit these descriptions, however, a few cat breeds closely mimic their native populations of origin. Genetic tests are available for the cat, which define a majority or their colours, fur types, and morphological traits. Cats can be genetically defined to their breed and to their populations of origin from various regions of the world. Many genetic diseases can now be monitored and tests can prove parentage and percentage of wild felid genetic contributions in hybrid bree ds. Therefore, undesired colors, traits, and diseases can be avoided, even when breeding with cats of unknown ancestry. Armed with these genetic tools, cat breeders and registries can now make more informed decisions regarding the propagation of their bree ds with the wise selection of appropriate cats. While many cat breeds show high genetic diversity, implying healthy gene pools, other cat breeds clearly have gene pools that are insufficient for maintenance of a healthy genetic population. Because the DNA tests are available, easy to acquire, and relatively low cost, cat breeders and registries can easily consider outcrossing programmes that will not significantly sacrifice the breed standards. Most societies insist that humans have great responsibility to be humane and to treat animals with high regard and value. Animal welfare, which includes an animal’s health, must be at the forefront of ethics for the cat fancy. The proper use of genetic tests and cooperation between the registries and breeders and amon gst the breeders can support healthy futures for cats and their breed populations. 2 GCCF policy on the use of outcrossing in cat breeding programmes Outcrossing is the introduction of new genetic material into a breeding line or a breed’s gene pool. I t involves the mating together of cats of different varieties, different breeds or of a pedigree cat to a ‘foundation cat’ of unrecorded ancestry as part of a planned and coordinated programme to improve the genetic diversity and genetic health of a breed. It can sometimes also be used to introduce new, desirable traits to a breed. It is one of the most important tools that can be used by breeders to maintain or improve their breed’s genetic health and guard against the negative health consequences of inbre eding and closed gene pools. An outcross programme is a long term undertaking that can require a commitment to breed through several generations. Why is Outcrossing necessary? 1) Combating inbreeding depression Inbreeding is the mating together of rela ted individuals. There are various degrees of inbreeding, the closest of which is first degree inbreeding, or the mating together of two siblings or a parent with its offspring. First degree inbreeding is now not considered acceptable and offspring of such matings cannot normally be registered on the GCCF active register because the kittens produced have very high inbreeding levels, with coefficients of at least 25% and an increased risk of genetic health issues. Line breeding is the mating together of less closely related individuals and almost all pedigree breeding involves some sort of line breeding as the creation of pedigree breeds relies on establishing foundation individuals and breeding like to like. Most pedigree animals have a certain level of back ground inbreeding but with a sufficiently large and diverse gene pool these levels can be kept low and remain sufficiently safe. When a gene pool is small because it has a low number of founders, or has been through a population bottleneck, then inbreeding levels can rise even from matings between individuals which are apparently not closely related. Any breed, breeding line or individual can suffer from inbreedin g depression when inbreeding co efficients are raised to high levels and a loss of heterozygosi ty results. Inbreeding depression can result in a general loss of vigour, even if the animals in question are not suffering from specific recessive genetic diseases. A small gene pool can result in inbreeding depression in a breed. A popular and numerous b reed with a small gene pool has a low 'effective population size', regardless of the numerical size of the breed's population. Inbreeding depression can compromise a cat's immune system and make it less able to resist disease. A group of genes called the M ajor Histocompatability Complex ( MHC ) plays an important role in the immune system. Because the genes in the MHC are inherited as a large cluster it is particularly vulnerable to inbreeding depression and a loss of genetic diversity in the MHC can impact on the health of the cat and its ability to fight diseases . Inbreeding depression can manifest in different ways depending on the particular make - up of the gene pool in question. Few cases of inbreeding depression will manifest all of the signs. Although these are problems which can occur in any random - bred cat, a combination of some of these signs could well indicate a problem with inbreeding depression. A breeder who is worried 3 about inbreeding levels in their lines should consider introducing cats from different lines or outcrossing to approved breeds. Signs o f inbreeding depression that have been demonstrated in other domesticated breeds include s low growth rate , s mall adult body size , s mall litter size , r educed fertility , i ncreased kitten mortality , i ncreased prevalence of allergies , r educed ability to fight infections , physical asymmetries - especially facial , an i ncrease in congenital abnormalities , i ncreased prevalence of cancers , i ncreased incidence of genetic disease , and r educed life expectancy . L evels of Coefficients of Inbreeding (COIs); Percentage Level Comments 0 to 10 % Low COIs which fall within this low banding are ideal 10 to 20 % Fair COIs which fall within this banding are reasonable and acceptable 20 to 25% Close COIs which fall within this banding represent close matings approaching the higher end of what breeders should normally consider 25 to 40% High Matings producing higher COIs than first degree matings should only ever be undertaken by experienced breeders for very specifi c reasons. If offspring are retained for breeding they should only be used for matings producing low COIs. 40%+ Not advised The welfare and health of cats with such high levels of inbreeding is highly likely to be compromised and such matings should not b e undertaken. Inbreeding coefficients should ideally be calculated back to foundation (i.e. the original cats used to found the breed) in order to give the most accurate reading possible. Many breed clubs hold databases and many breed databases are publi cly available on line at websites such as pawpeds.com so help is available for breeders wishing to calculate as far back as possible. Breeders who have no options for matings with inbreeding coefficients within safe levels have effectively bred themselves into a corner and should consider progressing by carrying out an outcross mating. However, it should not be assumed that recorded pedigrees are 100% accurate. G enetic parentage testing has never been used to doc ument the accuracy of pedigrees and any err or in a pedigree could potentially cause a significant miscalculation in an inbreeding estimation . Outcrossing is necessary to address high inbreeding levels and maintain genetic diversity within a breed’s gene pool. With each outcross mating inbreeding levels fall and genetic diversity rises, providing benefits to the overall health of the gene pool. Why is Outcrossing necessary? 2) Combating g enetic erosion Genetic erosion is the process by which all closed gene pools gradually shrink over time and gen etic diversity declines. All individuals have a unique combination of genes and genetic 4 erosion happens when individuals are neutered or die before being able to breed and pass on their genes. In cats the vast majority of kittens are neutered and are not u sed for breeding so the process of genetic erosion occurs more rapidly than it would in an endangered wild species. All closed gene pools are subject to genetic erosion although the process can be slowed down with good management, such as not keeping males at stud for too many matings and careful cooperation between breeders. A breed which has kept a closed gene pool for too long will experience loss of diversity and be at risk of the health problems associated with high inbreeding coefficients. Any breed w ithout an active outcross programme in place will experience a gradual decline in genetic diversity so outcrossing is vital for the long term health of all breeds. A steady trickle of new blood coming into a breed balances this gradual loss. Breeders can a ddress this by maintaining outcross options and promoting their appropriate use. Why is Outcrossing necessary? 3) Combating genetic drift Genetic drift is the process by which the frequency of a particular gene increases or decreases within a gene pool ov er several generations. It takes place because not all individuals in each generation contribute their genes to the next generation to the same degree. Some individuals may not contribute to the next generation at all, others may only pass on their genes t o a few offspring, while others may be prolific breeders.