Interação genótipo x ambiente e estimativas de parâmetros genéticos de características ponderais de bovinos Nelore.

Abstract

Body weight records at 90 (90W), 205 (205W) and 365 (365W) days of age of 46,408 animals born from 1976 to 2000 in 530 Nelore herds of several States of Brazil were used to estimate genetic parameters, evaluate the effect of genotype by environment interaction and rank the sires in each region. Genetic and maternal effects were estimated by restricted maximum likelihood methodology using two different statistical models, a univariate model and a bivariate model with the fixed effects of contemporary group, age of cow (covariate) and genetic and maternal random effects. Antagonisms between direct and maternal effect were observed for 90W, 205W and 205W traits. The genetic correlation for 205W and 365W, every one considered as different traits in each of South (S), Southeast (SE), Central West (CO), North (N) and Northeast (NE) regions were 0.86 e 0.84, 0.64 e 0.35, 0.75 e 0.42, 0.79 e 0.86, 0.92 e 0.81, 0.95 e 0.83, 0.83 e 1.00, 0.88 e 0.81, 0.33 e 0.85, 0.63 e 0.99 for S/SE, S/CO, S/N, S/NE, SE/CO, SE/N, SE/NE, CO/N, CO/NE and N/NE, respectively. These results indicated a significant genotype by environment interaction for 205W in the combination involving the South/Central West, South/North, South/Northeast, Central West/Northeast and North/Northeast regions. For the 365W there were significant genotype by environment interaction effects in the combination involving the South/Central West and South/North regions. These results also indicated that is necessary a regional genetic evaluation when considering very distinct regions.