Parâmetros genéticos entre características de leite, de peso e a idade ao primeiro parto em gado mestiço leiteiro (Bos taurus x Bos indicus)

Genetic correlations between milk production (milk, fat, protein yield lactation length in 305-d lactation), live weight (average cow live weight, growth rate between 12-24 mo) and age at first calving traits were estimated in a population of Mestico Leiteiro Brasileiro (MLB) females using REML methodology and animal model. The estimates of heritability were respectively, 0.28± 0.08, 0.30±0.11, 0.28±0.09, 0.19±0.07, 0.18±0.06, 0.42±0.10 and 0.48±0.12 for those traits. Genetic correlations between milk, fat and protein yield with cow average weight were, respectively, -0.22±0.22, -0.49±0.31, -0.22±0.23, and between milk, fat and protein yield with heifer live weight gain, -0.59±0.35, -0.73±0.44, -0.62±0.37 as well. Genetic correlations between milk yield, cow average weight and heifer live weight gain with age at first calving were, respectively, 0.05±0.18, -0.05±0.18, 0.02±0.20. The high genetic correlation between milk production and lactation length (0.93±0.02) indicated that variation of the lactation length should not be removed when selecting tropical dairy cattle.