Estimation of genetic parameters for preweaning growth traits of Brahman cattle in Southeastern Mexico.

The genetic parameters for Brahman cattle under the tropical conditions of Mexico are scarce. Therefore, heritabilities, additive direct and maternal correlations, and genetic correlations for birth weight (BW) and 205 days adjusted weaning weight (WW205) were estimated in four Brahman cattle herds in Yucatan, Mexico. Parameters were estimated fitting a bivariate animal model, with 4,531 animals in the relationship matrix, of which 2,905 had BW and 2,264 had WW205. The number of sires and dams identified for both traits were 122 and 962, respectively. Direct heritability estimates for BW and WW205 were 0.41 ± 0.09 and 0.43 ± 0.09, and maternal heritabilities were 0.15 ± 0.07 and 0.38 ± 0.08, respectively. Genetic correlations between direct additive and maternal genetic effects for BW and WW205 were -0.41 ± 0.22 and -0.50 ± 0.15, respectively. The direct genetic, maternal, and phenotypic correlations between BW and WW205 were 0.77 ± 0.09, 0.61 ± 0.18, and 0.35, respectively. The moderate to high genetic parameter estimates suggest that genetic improvement by selection is possible for those traits. The maternal effects and their correlation with direct effects should be taken into account to reduce bias in genetic evaluations.