Mating Systems To Avoid Inbreeding

Inbreeding is the mating of relatives. Inbred animals have a certain probability of inheriting the same gene variant from each parent, identical by descent from a common ancestor. This probability is the inbreeding coefficient, F. Inbreeding causes reduced merit, expression of recessive defects, and reduction of genetic variation within lines.

The obvious way to avoid inbreeding is to avoid mating relatives. However, this is really only effective in the following generation, unless we can import unrelated stock of sufficient genetic merit on a regular basis. For the longer term, we should avoid using few animals as parents a practice that inevitably leads to inbreeding. In some cases, such as a threatened gene pool, this is unavoidable, and the inevitable can be delayed by planning matings over a few generations to avoid mating relatives. However, this is not appropriate in genetic improvement programs, due to loss of selection differential.

There is a balance required here, as few parents give more selection differential, yet more inbreeding. The solution is to optimize the number of matings allocated to each breeding candidate to achieve a targeted combination of genetic gain and rate of inbreeding.[2] When applied, such a scheme gives more matings to animals of higher genetic merit, and to fewer related ''new blood'' animals.

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