Parâmetros genéticos e tendências genética e fenotípica para características de crescimento em uma população da raça Brangus

This study aimed to estimate the genetic parameters and genetic and phenotypic trends for weight at weaning (PD), yearling weight (PS), average daily gain from birth to weaning (GMDND), average daily gain from weaning to yearling (GMDDS), days to reach 160 kg at the pre weaning phase (D160) and days to reach 240 kg at post weaning phase (D240) of Brangus cattle raised in 37 farms in South, Southern and Mid Western Regions of Brazil, from 1987 to 2001. Records on 9,573 Brangus animals, sired by 415 bulls and 7,297 dams, were used to estimate (co)variance components by REML.The model included the genetic group of bull and dam and of contemporary group, age of cow at deliver, age at weaning weight and age at yearling weight covariate (linear and quadratic componentes) as fixed effects and the direct additive genetic, maternal and residual as random effects. The averages observed for PD, PS, GMDND, GMDDS, D160 and D240 were 171.62 kg, 306.2 kg, 0.701 kg, 0.395 kg, 234.97 days and 720.52 days, respectively. The direct heritabilities ranged from 0.15 (D240) to 0.45 (GMDND) and the maternal from 0.20 (PD) to 0.28 (GMDND). The genetic and phenotypic trends were 7.59 g/year and 0.864 kg/year; 5.16 g/year and 2.274 kg/year; 0.036 g/year and 0.007 kg/year; 0.011 g/year and 0.012 kg/year; -0.11 days/year and -1.59 days/year; -0.78 days/year and -9.79 days/year, respectively, for PD, PS, GMDND, GMDDS, D160 and D240.