Genetic evaluation in the presence of genotype-environment interaction in Nellore cattle: application of genomic tools

Abstract

The availability of genomic tools has allowed the identification of loci related to some traits economically important, however, there are no association studies considering the biotypes (set of traits or phenotypes desired) in different environments. These tools can also be used for prediction of genomic breeding values of the different biotypes and assist genetic evaluations, contributing to the increase in efficiency of beef cattle production systems. Thus, this project has the aims of identifying the most appropriate biotype of Nellore cattle, for different environments, by principal component analysis and reaction norm models; explore, with genome-wide association studies, genomic regions associated with the phenotypic expression of different biotypes in different environments; and to evaluate the predictive ability of genomic selection for the different biotypes in different environments. Data from Aliança Nelore will be used, comprising information of approximately 500,000 animals at weaning and 330,000 at yearling, which were born between 1984 and 2014. The data are from approximately 246 farms participating in different breeding programs, located in the Southeast, Center- west and Northeast of Brazil, and in Paraguay. Phenotypic observations of nine traits will be considered, namely: weight gain from birth to weaning, conformation, precocity and muscularity at weaning, weight gain from weaning to yearling, conformation, precocity and muscularity at yearling and scrotal circumference adjusted for age and yearling weight. The reaction norm model will be applied first, in which the genetic values will be obtained (EBV) for different environmental gradients; later, the principal component analysis will be applied to the different gradients, using as original variables the EBVs of the principal components, where biotypes will be characterized by the eigenvectors of the components and then these EBVs will be used in genome-wide association and genomic prediction studies. (AU)