Genetic evaluation of growth and reproductive traits in Nelore cattle under humid tropical conditions.

Assessing the genetic variability of economically important traits is key to guiding selection strategies, and monitoring its changes over time provides critical support for decision-making. The study aimed to estimate genetic parameters and evaluate genetic and phenotypic trends for growth and reproductive traits in Nelore cattle raised under humid tropical conditions. Growth traits included weaning weight (n = 1266), yearling weight (n = 832), and post-yearling weight (n = 733); while reproductive traits included age at first calving (n = 639), calving interval (n = 1772), and stayability (n = 1122), recorded from 2016 to 2022. Variance components were estimated using Bayesian inference, and temporal trends were assessed through linear regression of phenotypic and genetic values on birth year. Growth traits showed moderate to high heritability (ranging from 0.43 to 0.58), indicating good potential for response to selection. Reproductive traits exhibited low heritability (0.04-0.13), reflecting greater environmental influence. Favorable phenotypic trends were observed for weaning weight (3.09 kg/year), yearling weight (2.72 kg/year), post-yearling weight (3.91 kg/year), age at first calving (- 0.68 months/year), and calving interval (- 11.90 days/year). Genetic progress was observed for age at first calving (- 0.03 months/year) and calving interval (- 3.35 days/year), while the remaining traits showed no significant changes. These findings support the use of growth traits for genetic improvement while reinforcing the importance of integrating selection with management strategies to enhance reproductive performance of Nelore cattle under humid tropical conditions.