Association study among carcass and meat traits with growth traits in Nelore cattle

Abstract

In Brazil, in most breeding programs for beef cattle have been prioritized selection for growth traits such as weights or gains in different periods. In the literature, studies relating genetic associations between the growth traits taken of the animal in vivo, and carcass traits and meat measured in post-mortem are scarce. Despite its importance, genetic improvement for these traits has not been practiced, probably because of the difficulty and cost of measuring them. A few breeding programs have used the technique of ultrasound to assess ribeye area and fat thickness, but the selection for these traits is still limited. Moreover, in most international studies in which quantified the magnitude of genetic variation within breeds for carcass traits and meat were used Bos taurus. Thus, the aim of this project is to study the genetic relationships between the quantitative growth traits, commonly used as selection criteria in breeding programs, and carcass traits and meat after slaughter measures of Nellore cattle in order to propose alternative for genetic improvement of these traits through selection. Are used from approximately 1000-1500 of male animals Nellore finished in feedlot aged around two years, from farms that are part of the breeding program of Conexão Delta G. Will be evaluated for carcass traits and meat: carcass weight, ribeye area, backfat thickness, tenderness and marbling index. The growth traits to be evaluated are: weaning and yearling weight, yearling height and weight gain from weaning to yearling. The models to be used for the (co)variance estimates of random effects include additive genetic effect, maternal genetic and maternal permanent environment (for weaning weight) effects and, as fixed effects, the contemporary group and other effects, depending on the trait. The importance of effects such as age and / or weight of the animal, and number of days in confinement on the traits will be tested. The (co)variance components will be estimate by restricted maximum likelihood method. This project will allow the estimation of genetic parameters for carcass and meat traits, and verify their possible association with growth traits. Will be possible check the validity of the use of growth traits as indicators of carcass traits and meat traits for breeding purposes and for selection of animals for slaughter.