Genetic relations between the number of calving before 53 months, rebreeding subsequent of primiparous, ability to stay and scrotal circumference in Nelore cattle

Abstract

The reproductive efficiency of the herd presents considerable improvements by identifying and multiplying the genotypes most appropriate to the production system and also the environmental conditions conducive to expression of these genes. Identify reproductive characteristics with easy measure, economically importance with potential selective is essential. Herds with high fertility and sexual precocity have a greater availability of animals, whether for sale or for selection, allowing more intense selective and, consequently, higher genetic progress. This study aims to estimate heritability for the traits number of calvings before 53 months, redesign of primiparous stayability up to 72 months, scrotal circumference (SC), to establish correlations between genetic and phenotypic and calvings before 53 months and the other features, seeking the possibility of using the features directly measured in females as selection criteria for genetic improvement in Nelore cattle. It is intended to estimate the (co) variance and genetic parameters for the characteristics mentioned by Bayesian inference, using the software THRGIBBS1F90 (Misztal et al., 2002). Calvings before 53 months, rebreeding subsequent of primiparous and stayability will be analyzed assuming a threshold model, which relates the observed response (in discrete scale) to an underlying normal scale, while the characteristic SC will be analyzed under a linear model, including the effects age and weight as covariates. (AU)