Can scrotal circumference-based selection discard bulls with good productive and reproductive potential?

摘要: Nonlinear mixed models were used to describe longitudinal scrotal circumference (SC) measurements of Nellore bulls. Models comparisons based on Akaike’s information criterion, Bayesian error sum squares, adjusted R2 and percentage convergence. Sequentially, the best model was compare SC growth curve in bulls divergently classified according at 18–21 months age. For this, into five groups: < 28cm; 28cm ≤ 30cm, 30cm 32cm, 32cm 34cm ≥ 34cm. Michaelis-Menten showed fit mentioned criteria. In this model, β1 is asymptotic value β2 represents time half-final may be related sexual precocity. Parameters individual estimated curves create a new dataset evaluate effect classification, farms, year birth parameters. Bulls largest group presented larger predicted along all analyzed periods; nevertheless, smaller similar intermediate groups (28cm 32cm), around 1200 days context, as improper for reproduction old can reach condition those considered good condition. terms classification months, among groups, farms years; however, differed indicating that differences are summary, it seems selection too early ages lead discard with suitable reproductive potential.