Data from 273 Nellore bulls borned from 1992 to 1998 and with average age of 31 month were used to estimate by restricted maximum likelihood procedure the heritability for scrotal circumference (SC), libido (LIB), sperm motility (MOT), vigor (VIG), concentration (CON) and porcentage of defects (PD) and the genetic correlations between these traits. The heritabilities estimates and standard errors were 0.38±0.20 for SC, 0.33±0.20 and 0.31±0.20 for LIB, when age and body weight were included in the model, 0.01±0.10 for MOT, 0.03±0.30 for vig, 0.00±.0.50 for coN, and 0.07±0.13 for PD. Otherwise, genetic correlations between SC and LIB were 0.78 and 0.76, respectively, including or not including body weight in the model. Genetic correlations between SC and the traits CON, MOT, VIG and PD were 0.99, 1.00, -0.14 and 0.99, respectively. Responses to direct selection are expected for SC and LIB, and selection for one trait would result in gain for the other. Heritability estimates for semen traits indicate small genetic additive components for the traits.
Beef cattle; Nellore; genetic parameters; reproduction