Associations between reproductive and carcass traits in Nellore

Abstract

The objective of this study was to estimate the genetic parameters and (co)variance of Nellore animals and to characterize the associations between these characteristics for the following carcass traits: weight (W), longissimus muscle area (LMA), rump fat thickness (RF) and fat thickness between the 12th and 13th ribs obtained by ultrasound (BF); also, the following reproductive traits: age at first calving (AFC), first calving interval (FCI), scrotal circumference at 450 and 550 days of age (SC450 and SC550). The genetic parameters were estimated by a single-trait and two traits animal model using Bayesian inference. The model used for all of the features included the genetic random effect and age as covariate assuming a quadratic effect. Additionally, sex, month and year of birth and management of creation and environmental effects identified were included for the carcass traits. For AFC, FCI and SC450 and SC550, we considered only the month and year of birth. The heritability estimates for all of the traits were higher in the two traits analysis, except for AFC and FCI, which showed 0.75 and 0.29, respectively, similar values in the single trait analysis. The two traits analyses resulted in heritability estimates for a posteriori for the features W, LMA, BF, RF, SC450 and SC550 of 0.49, 0.66, 0.74, 0.68 0.66 and 0.74, respectively, suggesting the possibility of genetic gains during a short period of time. The genetic correlations between AFC and carcass traits measured by ultrasound were close to zero. A similar trend was found for AFC, SC450 and SC550 days, indicating that the selection for these traits does not promote changes in AFC. High genetic correlations (0.92, 0.93 and 0.94) were observed between the characteristics LMA and W, BF and RF, and SC450 and SC550, respectively.