Four methods of pedigree indexing young bulls for artificial insemination were compared relative to subsequent progeny tests on the same bulls. Because many young bulls entered in Canadian AI units are progeny of parents from the United States, formulas for converting US genetic evaluations into Canadian equivalents were utilized. Indexing Method 1 averaged the (converted) genetic evaluations of the sire and dam. Method 2 was based on derived coefficients from the regression of progeny genetic evaluations on sire and dam genetic evaluations. Method 3 was the same as Method 2 except Canadian dam genetic evaluations were adjusted to eliminate the influence of their son(s) on their genetic evaluations due to an automatic correlation between sons and dams arising from animal model evaluation procedures. Method 4 was the same as method 1 except the adjusted dam index was used for parental averages. Pedigree indexes from Method 1 overpredicted young bull merit on average, while the other three methods gave means similar to progeny test evaluations. Method 2 gave more weight to Canadian dam genetic evaluations, because of the auto-correlation with sons’ evaluations, than on US dam genetic evaluations, which did not include their Canadian sons’ information. Method 3 gave the best predictions, but rankings were similar to those of Method 1. Correlations among the pedigree indexes and eventual proofs for traits in the Lifetime Profit Index ranged from .6 to .8, and were similar for all four methods. Of the top 40% of young bulls on the basis of pedigree indexes, 86% (93 out of 108) were also in the top 10% on actual proofs. Not one bull with a PI in the bottom 30% had an actual proof that reached the top 10%, except 2 bulls when PI were computed by method 4.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 11–14, 1994
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