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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) of sires that were heavily used in the past. Such excessive use of a few breeding animals has a marked increasing effect of the average additive relationship in the population causing inbreeding problems in future generations. In populations they create genetic bottlenecks in populations.

The excessive use of popular sires often lead 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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A positive reaction to the excessive use is to make and propagate a plan in which all selected sires get an equal number of matings. They approach the optimal and sustainable schemes of well controlled breeding programs.

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