Inbreeding in swine
Inbreeding is the mating of individuals that are related. In the strict sense, all members of a breed are related. As a result, any seedstock producer is practicing some inbreeding. Therefore, we generally reserve the term inbreeding for the mating of animals that are more closely related than the average of the breed.
Most breeds of livestock went through a phase of inbreeding early in their development. This resulted from the desire to establish colour patterns and other aspects of physical appearance. Since one of the results of inbreeding is to establish more genetic uniformity, those traits, such as colour, which have simple means of inheritance can be fixed more easily with the aid of inbreeding.
Inbreeding can have dramatic effects on a herd. These effects are the result of individuals receiving identical genes from each parent. If the parents are related it is more likely that they have genes that are identical. When an individual receives an identical gene from each parent, it is said to be homozygous for that pair of genes. This would be desirable if the gene it received from each parent leads to superior performance. However, most animals carry undesirable genes that usually remain hidden unless the animal has a pair of them. An inbred individual is more likely to have gene pairs with identical members, and so is more likely to express undesirable genes. This leads to a decline in performance called inbreeding depression. This phenomenon is well documented in all of the major livestock species. It is essentially the opposite of heterosis, which is the advantage gained from crossing lines or breeds.
The article will cover at least four inbreeding topics, which are:
Inbreeding can have several benefits to a seedstock producer if the breeder understands how to monitor it and is willing to sacrifice some performance in the process. Inbreeding tends to subdivide a breed into families which can be identified and crossed with some small benefit.
The article will also offer recommendations in regard to inbreeding.
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Article made possible through the contribution of Oklahoma State University.