The objective of this study was to estimate heritability of scrotal circumference at 12 months of age (SC12), age (AFC) and weight (WFC) at first calving and genetic correlations between each of these traits and the following growth traits: weight at birth (BW), weaning (WW), twelve (W12) and eighteen (W18) months of age, weight gain from birth to weaning (DGBW) and from birth to eighteen (DGB18) months of age, days to 175 kg from birth to weaning (D175 = 175/DGBW) and days to 450 kg from birth to slaughter (D450 = 450/DGB18). Data from a Canchim (5/8 Charolais + 3/8 Zebu) beef cattle herd were analyzed by models that included fixed effects and the additive direct and maternal, permanent environmental, and residual random effects using REML. Heritability estimates were 0.41 (SC12), 0.09 (AFC) and 0.42 (WFC). Genetic correlations of BW, WW, W12, W18, DGBW, DGB18, D175 and D450 with SC12 (-0.39 to 0.46) were favorable. Genetic correlation between BW (0.49) and AFC was not favorable, while with the other growth traits (-0.38 to 0.44) AFC showed favorable genetic correlations. Genetic correlations between WFC and growth traits ranged from -0.47 to 0.88, while the estimates of SC12 with AFC and WFC were -0.37 and 0.04, respectively. These results suggest that selection to improve growth after birth may reduce AFC and increase WFC. Selection to increase SC12 may reduce AFC without changes in WFC.
beef cattle; body weight; genetic correlation; precocity; weight gain
