Since 1967, the United States Department of Agriculture has used the herdmate comparison method to calculate dairy sire genetic evaluations. This method is based on the assumptions that all herdmates are drawn randomly from one genetically homogeneous population, that there is no genetic trend in this population, and that bulls’ daughters and their herdmates are subjected to the same severity of culling for milk and milk fat yield. These assumptions are no longer valid, primarily because of the success in identifying genetically superior bulls for use in artificial insemination in the United States since the wide use of the herdmate comparison method. Therefore, research has been conducted for several years on Sire Summary methods that will eliminate these assumptions and permit the accurate genetic evaluation of all dairy bulls. Two separate methods are being developed, and computing systems have been designed and programmed for each.

F. N Dickinson

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 2, Madrid, Spain, 111–118, 1974
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