Rob Ellett
UKC Forum Member
Registered: Jun 2003
Location: Armstrong,IL
Posts: 3348 |
Inbreeding
Inbreeding seems to scare the beejabbers out of some people. For those people who cannot destroy defective dogs, it should. For those serious breeders who can cull and carry on, it will eventually become an option. It is an extremely useful tool for diagnosing what genes are present. If the genes for bad eyes are present, but hidden or resessive, this will bring them out to their full extent. If there isn't any bad genes, then the puppies will be of very close uniformity and very able to reproduce themselves (theroretically).The resulting puppies will have a lot of genetic material that is the same as their parents and grandparents and will be close genetically to each other.
What is meant by inbreeding is this; breeding two dogs that are closer than cousins. Typically the
combinations are brother/sister, father/daughter, mother/son, and on the looser side, cousin to cousin, grandfather/granddaughter, half-brother and halfsister. You get the idea. The dogs should have or be common ancestors. People disgree about the exact point at which inbreeding becomes linebreeding but inbreeding is the quickest way to find out what poor genes are in the line and what dominant characteristics are in the line.
Genetically what inbreeding does for you is concentrate the traits in your stock, both good and bad and that is stressing good and bad. The bad is as important as the good. While you are fixing all those good traits in your population, a hidden trait may crop up that can wipe you out if you aren't careful. This is the down side of inbreeding. When those traits appear, the affected animal must be removed from the breeding program.
Inbreeding doesn't introduce new genes and does not eliminate bad genes that the line already has. It only shifts them around like a rubix cube. This often results in litters with high show potential, if the quality was high to begin with. It shows you what recessives you have lurking in the dogs' backgrounds, both good and bad. But there are drawbacks. Besides the possibility of bad recessives, inbreeding exclusively over time will eventually lead to infertility. It's like a xerox machine. After so many copies, you have to renew the ink. The same with dogs, you have to introduce new genes. No reputable breeder will use inbreeding exclusively, and many breeders simply never use it.
Inbreeding increases homozygosity and decrease heterozygosity. Homozygosity means that certain traits will double up so that no matter what the dog is bred to it will carry on those specific traits. Heterozygosity means that more genes will be in a single dose and less likely to show up in any given trait. So inbreeding can duplicate both desirable and harmful genes, both of which can be unsuspected in the line, and may appear. Inbreeding does NOT create anomalies, it brings present anomalies to the surface. Even when the anomalies are present, inbreeding might not reveal them. However, once revealed, then the breeder can do something about them in the next generations of breeding.Usually, you will only find: very experienced breeders, ignorant breeders, and puppy mills making use of this technique.
Let's say that you've been inbreeding for a couple generations and you now have a genetic defect in your entire breeding population. Keep inbreeding, looking for those one or two clear animals and use them because they are almost exclusively clear of the problem. An increase in harmful recessives is undesirable but it is not a major drawback if they are identified early. The effect of inbreeding on major polygenic traits is greater. Generally, traits that are highly inherited or ones which are many genes added together to produce the defects, are not adversely affected by inbreeding but, traits under non-additive control, especially those tied to dominance and not of high heritability, are often markedly harmed by inbreeding.
Inbreeding is not for the faint of heart or those unwilling to keep their pups long enough to make
positive assessments. But for those who are breeding with a goal in mind, it gives them much greater
control over their gene pool and a direction to head towards knowing what exactly they are dealing with in thier dogs.
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01-30-2006 11:14 PM
