Multi-breed models enable across-breed selection by calculating estimated breeding values (EBV) for crossbred animals and providing routine estimates of breed differences and heterosis. Evaluations for U.S. dairy cattle recently were revised to account for inbreeding, and a multi-breed model that accounts for heterosis was tested for yield, somatic cell score, longevity and daughter pregnancy rate. Convergence of the multi-breed and current within-breed animal models was similar; correlations of across- and within-breed EBV were >0.99 for Holsteins and slightly <0.99 for other breeds. Genetic interactions between sire and maternal grandsire (MGS) also were examined within breed for U.S. Holstein milk yield and productive life. Largest sire-MGS interactions were not quite as large as estimated heterosis across breeds (3.4% of mean) for milk yield but were larger (4% of mean) than heterosis for productive life.

P. M VanRaden

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.39, 2006
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