Genômica para prospecção de genes de interesse econômico em bovinos Nelore

Abstract

Cattle breeding have a major impact on the Brazilian economy, bringing to the need for more productive animals, capable of maintaining a growing production line, without the conversion of important biomes into pasture areas. Thus, the genome wide association study (GWAS) it is justified, for the identification of markers associated with age at first calving (AFC) and weight at different ages for Nellore cattle. The sample group was decomposed into G1, containing 2273 animals (995 males and 1278 females) genotyped to more than 777,000 panel-markers and G2 (522 females) genotyped with high density than 50,000 markers, which had the genotypes imputed to a more dense panel. The genomic data were submitted to quality control, aiming the removal of markers or biased samples, before and after the imputation. The markers were organized in haplotypic blocks, containing 5 markers each. For AFC the GWAS was performed using two meta-analysis methodologies, the first one considered the independent populations between modeling and the second the existence of correlation between the populations. For weight phenotypes, the association study was based on a linear mixed model. The results were exposed in Manhattan plot. Those haplotypes whose estimated effects were major and/or significant were explored to examine the proximity to cataloged bovine QTL and genes. For reproductive traits, 9 genes and 45 QTLs were found for 1 analysis, while for meta-analysis 2, 11 genes and 129 QTLs. It was possible to identify the characteristics of birth weight, weaning weight, yearling weight, weight gain from birth to weaning and weight gain from weaning to yearling, respectively, 7, 9, 4, 4 and 5 genes. Regarding the QTLs, 25 presented biological function associated to the weight characteristic. The GWAS using the haplotype allele approach proved to be efficient in the search for genetic variants associated with the phenotypes of interest.