Estimation of genetic parameters for probability of calving up to 39 months of age, stayability and scrotal circumference in Nelore cattle

Abstract

Improving reproductive indexes is of extreme importance in beef cattle production systems, as well as investigating new methodologies and traits in order to increase genetic gains for reproduction. Reproductive efficiency directly affects the profitability and productivity of herds, being an important criterion in breeding programs. The objective of this study was to estimate genetic parameters in a Nelore cattle population for probability of calving up to 39 months of age (PC39), stayability, using two measures of age (STAY64– 64 months of age; and STAY76– 76 months of age), and for scrotal circumference at weaning (SCW) and 550 days of age (SC550). Genetic parameters were estimated using 2,287,827 records collected from 1901 to 2015 in Nelore cattle belonging to the Geneplus beef cattle breeding program (Campo Grande, MS, Brazil) database. Bayesian procedures were applied in single- and two-trait analyses using the GIBBS2F90 and THRGIBBS1F90 software, for linear and threshold analysis, respectively. Heritabilities from single-trait analysis were 0.15, 0.23, 0.20, 0.28, and 0.36 for PC39, STAY64, STAY76, SCW, and SC550, respectively. The correlation between PC39 and scrotal circumference were of low magnitude, 0.20 and 0.25 with SCW and SC550, respectively, suggesting that the selection for SC550 in sires would possibly lead to higher changes in PC39 occurrence than selection for SCW. The reproductive traits comprised in this study should be included in Nelore cattle breeding programs. Especially PC39, STAY64, and SC550 because its traits would increase the indexes reproductions of the production system.