Estimativas de parâmetros genéticos para características produtivas e reprodutivas em búfalas leiteiras

Abstract

Knowing the genetic parameters of productive and reproductive traits in milking buffaloes is essential for planning and implementing of a program genetic selection. In Brazil, this information is still scarce. The objective of this study was to verify the existence of genetic variability in milk yield of buffaloes and their constituents, and reproductive traits for the possibility of application of the selection. A total of 9,318 lactations records from 3,061 cows were used to estimate heritabilities for milk yield (MY), fat percentage (%F), protein percentage (%P), length of lactation (LL), calving interval (CI) and age of first calving (AFC) and the genetic and phenotypic correlations among traits. The (co)variance components were estimated using multiple-trait analysis by Bayesian inference method, applying an animal model, through Gibbs sampling. The model included the fixed effects of contemporary groups (herd-year and calving season), number of milking (2 levels), and age of cow at calving as (co)variable (quadratic and linear effect). The additive genetic, permanent environmental, and residual effects were included as random effects in the model. Estimated heritability values for MY, %F, %P, LL, CI and AFC were 0.24±0.02, 0.34±0.05, 0.40±0.05, 0.09±0.01, 0.05±0.01 and 0.16±0.04, respectively. The genetic correlation estimates among MY and %F, %P, LL, CI and AFC were, respectively, 0.24, 0.34, 0.40, 0.09, 0.05 and 0.16. The milk yield and its constituents showed enough genetic variation to respond to a selection program. Negative estimates of genetic correlations between milk yield and its components suggest that selection entails a reduction in the other.