Genetic parameters for fertility indicator traits, biometric measurements and reproductive indices in Tabapuã cattle

Abstract

Over the years, the search for identification of precocious animals has been advancing due to the intense population growth and increased demand for animal protein. The demand from the market for breeding animals is essential for livestock advances, but some traits are not easy to select. The response to the selection of reproductive traits is slower, as they generally have low heritability, being greatly influenced by environmental factors. With the aim of accelerating the genetic improvement and selection of these reproductive traits, the search for early and easily measured fertility indicator traits is interesting, facilitating the field selection process. The aim of this work was to look for traits that indicate fertility in Zebu females, estimate the heritability and evaluate the genetic correlation between them. We collected data from 934 females, born between 1993 and 2020, evaluating traits such as vulvar size, antral follicle counts (AFC), concentration of Anti-Mullerian hormone (AMH), biometric measurements and reproductive indices of the breeding program of Zebu cattle (PMGZ) of the Tabapuã breed. The genetic parameters of the traits were calculated by Bayesian analysis using executables from the BLUPF90 family. The analyzes were carried out using a linear mixed model that included the effects of contemporary group formed by year of birth, farm and parity, in addition to the effects of age and weight class. The random effect of the animal itself was also considered. The heritability values obtained for most probable producing ability (MPPA) (0.88), anterior height (AH) (0.42), thoracic depth (TD) (0.37), rima length (RIMA) (0.32), age at first calving (AAFC) (0.28), antral follicle count AFC (0.24) and vulva width (VW) (0.20) demonstrate that they are traits responsive to direct selection. According to the estimates of genetic correlations, it can be concluded that there is no genetic correlation between the traits studied.