GM 29. Breeding group direct genetic contribution on milk production in tropical environments

Abstract

A total of 4 669 records from 55 herds was used to evaluate the effects of direct breed gene fraction and heterozygosity on milk yield at 244, 305 days, total, and days in lactation in tropical environments. Traits were analyzed by derivative-free REML. The final model included fixed effects of season: combination of year x month of calving, herd, and linear and quadratic effects of age at calving and linear effects of direct gene fraction of breed and heterozygosity as covariates. Random effects were animal genetic and permanent environmental effects. Holstein and Brown Swiss breed solutions were greater than for the other breeds with Zebu the smallest. Heterozygosity effects excelled in the additive means of groups but not the effect of the best of the breeds. The largest positive heterozygosity effects were for Bos indicus by Holstein and Brown Swiss and the largest negative heterozygosity effects were for Bos taurus by Bos taurus.