Genetic associations of sexual precocity with growth traits and visual scores of conformation, finishing, and muscling in Nelore cattle.

The objective of this study was to determine the possible use of heifer pregnancy at 16 mo as a selection criterion and its possible genetic associations with hip height, yearling weight, and visual scores of conformation, finishing, and muscling. The data set contained records of 56,458 Nelore yearlings for the traits described above. Covariance components were estimated by bivariate animal models assuming a linear model for hip height, yearling weight and conformation, and finishing and muscling scores, and a nonlinear (threshold) model for heifer pregnancy. Variance components were estimated using Bayesian inference. Flat distributions were used for all (co)variance components and genetic correlations. The first 5,000 rounds were considered as the burn-in period and discarded. The heritability estimate of heifer pregnancy indicates that the trait can be used as a selection criterion. Long-term selection for heifer pregnancy will result in a reduction of animal height. However, selection for increasing yearling weight should be possible in this population of Nelore cattle without having major effects on fertility. Selection for increasing visual scores of conformation, finishing, and muscling will result in small or no response in heifer pregnancy at 16 mo.