Data consisting of standardized weights at 120, 210, 365, 450 and 550 days of age (W120, W210, W365, W450 and W550), hip height at 18 months of age (HH) and standardized scrotal circumferences (SC) at 365, 450 and 550 days of age (SC365, SC450 and SC550) of Nelore animals born between 1998 and 2003, from ten ranches in six Brazilian States were used to estimate (co)variance components. Analyses were done by Restricted Maximum Likelihood methodology using single trait, two and three traits animal models. Heritability estimates of the direct effect for each trait and respective standard errors were: HH 0.63 (0.09), W120 0.25 (0.03), W210 0.34 (0.03), W365 0.45 (0.04), W450 0.48 (0.04), W550 0.49 (0.04), SC365 0.48 (0.04), SC450 0.53 (0.04) and SC550 0.42 (0.09). Genetic correlation estimates between HH and W120, W210, W365, W450, W550 were respectively 0.68, 0.64, 0.53, 0.58 and 0.59. Genetic correlations between W120 and SC adjusted for weight and age were close to zero, but positive and moderate when SC was adjusted only for age. Estimates of genetic correlation between HH and SC adjusted for weight and age were -0.19 (SC365), -0.24 (SC450) and 0.00 (SC550). The same parameter estimates when SC was adjusted only for age were 0.21 (SC365), 0.12 (SC450) and 0.39 (SC550). These results indicate genetic variability for growth traits and SC. Selection for weight at any age will increase stature. In order to obtain Nelore cattle with stature and weight suitable to the production system, both traits should be included in a selection index.
beef cattle; Bos indicus; genetic correlations; heritability; standardized weight
