The Healthy Continuation of Breeds Picture

Purebred dogdom is even now in serious trouble through a general failure to distinguish between what is necessary to establish a breed and what is desirable to continue that breed in perpetuity. Most registered breeds are less than a century old qua registered breeds; many are but fifty or sixty years old. Yet nearly all breeds now show levels of expression of genetic defects that must be considered unacceptable. Over 500 distinct genetic defects have been catalogued in various breeds of purebred dogs and more continue to come to light regularly. Some of these have reached very high levels of incidence, creating problems for breeders and dog owners, threatening the health of entire breed populations. What is worse, in many instances organised control programmes seem relatively ineffective. Although such programmes successfully identify affected animals, in some cases individuals with several generations of "clear" ancestry stubbornly continue to produce affected stock. Let us try to examine what has gone wrong and what must be done to correct the situation.

First of all it must be recognised that practices which were essential for the differentiation and establishment of a new breed may not necessarily be desirable for its continuation over time and may in fact be prejudicial to a breed's continued existence over the long term.

Let us take isolation, for example. Without genetic isolation, it would not be possible to control the genome of a new breed still few in number. It takes time and careful breeding to fix a new combination of characteristics; while that is being done, the regular addition of new genetic material would generally be counterproductive. Yet in the long term, if genetic isolation is maintained, it will necessarily lead to degeneration through genetic drift. Similarly inbreeding, if it continues to be practised after the need for it is past, will lead to a steadily increasing state of homozygosity which may well destroy the genetic health of the new breed. Even artificial selection, if carried on too strongly for too long, can combine with isolation and inbreeding to reduce drastically the effective breeding population, thus eroding the genetic health of the breed.

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