Posts Tagged ‘dog husbandry’

Virtually all working border collies used in trials are descended from this dog, "Wiston Cap."

Virtually all working border collies used in trials are descended from this dog, "Wiston Cap."

The Canine Diversity Project is a site worth visiting.

How do we create genetic diversity?

We do it by introducing new bloodlines in a population.

Why do we need to do this?

Because diversity gives a population some room. It prevents genetic diseases from become so heavily concentrated in the population. Further, if a  deadly new pathogen suddenly began to spread through the population, some of those individuals in that genetically diverse population might be resistant to it. The chance that this might happen is one reason why so many people are concerned about the genetic diversity of farm animals.

Zoos and breeding programs that produce endangered animals are always worried about genetic diversity. Inbred populations might have lower reproductive rates, as is the case with the cheetah, and the chance of a deadly pathogen killing off whole species is a major concern.

Until recently, dog people haven’t thought much about it.  Genetic diversity in most purebred dogs has been reduced through the advent of organized competitions and an institutionalized fancy. Further, most registries use closed studbooks that only allow new dogs to enter the breeding population for a short time. After this time is past, it is very difficult to add new bloodlines, although they can be imported from similarly closed registries.

Dog shows are often blamed for the problem. Dog shows make certain male dogs rather famous. Male dogs can produce far more offspring than bitches can, and what often happens is that winning studs are used many times. This use of winning studs within a population reduces genetic diversity, simply because so many dogs have the same sire. Over time, the number of dogs with the same sire in their pedigree increases, and because these dogs are more likely to be winners, they are bred together. This problem can happen without deliberately inbreeding. If a great many dogs have the same sire,  at some point, the progeny of these dogs wind up being bred together. If that sire was carrying a bad genetic disorder, you have increased the chance of large numbers of that particular dog population developing the disorder.

This problem is not confined to show dogs. In border collies, the popularity of sheepdog trials has had a similar effect. Virtually all working border collies today descend from a single sire, Wiston Cap. Border collies don’t have problems with an exaggerated body type, but they all pretty much have the same genetic disorders.

Although it is true that some species have survived great reductions in genetic diversity, such as the Northern Elephant Seal, which are all descended from a single male ancestor, it is not likely that dogs are going to be able to survive these severe reductions in genetic diversity. The wolves of Isle Royale (a long observed population) became severely inbred, and their population was unable to rebound for several years after the moose population dropped. Inbreeding is often suggested as one of the reasons for their inability to rebound once moose began to appear in higher numbers.

We need to really pay attention to genetic diversity in our dogs. It is as important as working conformation and temperament in ensuring the long-term viability of our beloved animals.

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