Quantitative study of genetic gain for growth, carcass and morphological traits of Nelore cattle

The aim of this study was to evaluate the genetic variability, genetic and phenotypic associations, and genetic gains of birth (BW), weaning (WW), and yearling (YW) weights, loin muscle area (LMA), backfat thickness (BF), rump fat thickness (RF), scores of body structure (BS), finishing precocity (FS), and muscling (MS) in Nelore cattle. Genetic parameters were obtained through Bayesian inference using BLUPF90 programs. All studied traits showed genetic variability, with heritability ranging from 0.29 to 0.47. In all studied ages, weights presented positive genetic correlations with LMA (ranging from 0.13 to 0.53), being generally stronger in comparison with the other carcass traits analyzed (BF and RF). Similarly, weights were higher genetic associated with BS (0.47 - 0.92) than with FS (0.18 - 0.62) and MS (0.22 - 0.65), respectively. The BF and RF showed positive and moderate genetic associations with FS and MS (0.31 - 0.36). Genetic trends were significant (P < 0.05) and favorable for WW, YW, and visual scores. Selection for increasing BW, WW, YW, and LMA will result in modest or no change in BF and RF (correlated response ranging from - 0.04 to 0.07 mm per generation). In this population, carcass traits must be included in the selection indexes to obtain genetic gains in carcass quality, if desired.