In well set up and controlled breeding schemes it is aimed to use the selected sires and dams with the same intensity. In the next generation they get an equal number of offspring. In that way the genetic variation in the population is maintained. All ancestors in the pedigrees of the parents return all in the pedigrees of the animals in the next generation. Such breeding schemes are optimal and sustainable: in future generations all opportunities for selection are still present. In less controlled populations we have a lot of examples of sires that were heavily used in the past in breeds of dairy cattle, horses and dogs. Such excessive use of a few breeding animals has a marked increasing effect of on the average additive relationship in the population causing inbreeding problems in future generations. In populations they create genetic bottlenecks.
The excessive use of popular sires often lead leads to a limited use of other sires or even neglecting sires that were selected for use. That contributes to the effects of genetic bottlenecks.
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