Genetic parameters of performance traits during the pre-weaning period in Nelore cattle

Abstract

The pre-weaning phase provides the first phenotypic information related to animal performance, allowing for the early evaluation of genetic potential. This study aimed to estimate the phenotypic means, heritability (h²), and genetic correlations (rg) of performance traits expressed during the pre-weaning phase in Nelore cattle. The traits analyzed were birth weight (BW), average daily gain (ADG), weaning weight adjusted to 205 days (W205), and days to reach 160 kg (D160), using data from 1,859 Nelore animals from the Embrapa GenePlus Program database. Variance components were estimated using a trivariate animal model using BLUPF90+ via the expectation-maximization algorithm. The statistical model included fixed effects of contemporary group (CG, n = 221, minimum 5 and maximum 26), defined by birth year (2012 to 2019), sex, birth season (1: October to March; 2: April to September), farm, and feeding regime (1: pasture; 2: semi-confinement), as well as cow age at calving (linear and quadratic) as a covariate. The means ± standard deviations for the traits were 32.67 ± 3.96 kg (BW), 0.77 ± 0.14 kg/d (ADG), 189.54 ± 29.64 kg (W205), and 217.29 ± 46.10 d (D160). The heritability estimates for BW, ADG, W205, and D160 were 0.19, 0.13, 0.14, and 0.13, respectively. Genetic correlations were of moderate magnitude: -0.33 (BW and ADG) and 0.35 (BW and D160); low: -0.02 (BW and W205); and high: -0.95 (D160 and ADG) and -0.94 (D160 and W205). The results indicate that heavier animals at weaning tend to reach 160 kg more quickly. The negative correlation between BW and ADG suggests that calves with lower birth weights tend to have higher daily weight gains. Therefore, it is possible to use early life traits to improve the growth performance of Nelore cattle through selection strategies targeting both pre-weaning weight and the growth dynamics of calves.