Environmental and genetic trends for productive characteristics in Nellore cattle.

The objective this work were estimates the genetic parameters, direct an maternal effects to pre weaning gain and days to gain 160 kg, daily average gain after weaning and days to gain 240 kg after weaning and evaluated the genetic and environmental trends in Nellore cattle. The estimates of variances components and genetic values were made with MTDFREML program, animal model. The model used to pre weaning estimates was included the random effects direct and maternal and the correlations between than, environmental permanent dam effect, which fixed effect used contemporaneous group and age of dam in the parturition which a covariate (Linear and quadratic). For post weaning characteristic used the same model without maternal and environmental permanent dam effect. The genetic and environmental trends were estimates using the regression analysis of genetic value by year and contemporaneous group by year. The heritability coefficient to direct, maternal and the correlations direct maternal, environmental proportion of total variance and phenotypic variance to gain pre weaning, D160 and gain pos weaning and D240 were 0.13 ± 0.02, 0.17± 0.03, 0.09 ± 0.016, 0.14 ± 0.01; 0.06 ± 0.03, 0.06 ± 0.02, ., .; -0.36 ± 0.17, -0.43 ± 0.14, ., .; 2,888.77, 0.01262, 52,356.94, 0.01374; and, 3,653.68, 0.01645, 57,278.94 and 0.01604 respectively. The direct genetic trend and environmental trend were positive showing gain in the fell years. Perhaps, the maternal genetics trends were negative. The maternal ability need careful to not make an inverse selection to this trait.