Genome-Wide Association Studies for Body Weight and Average Daily Feed Intake During the Feedlot Test Period

Abstract

Feed efficiency component traits such as body weight (BW) and daily feed intake are economically relevant traits in beef cattle breeding programs. The objectives of this work were to identify genomic regions associated with BW and average daily feed intake (ADFI) during the feedlot period, and to evaluate whether these genetic variants for each trait were consistent over the 70-day test period. Data on 2070 Angus steers were used to estimate (co)variance components using the genomic relationship matrix (gREML) fitted in ASReml. For the studied traits, a two-trait repeatability (TT-REPM) and a two-trait random regression (TT-RRM) models were performed. SNP-effects for the TT-REPM and TT-RRM were estimated using a post analysis back-solving approach using the genomic estimated breeding values from each model respectively. For each trait, results were validated with single-trait animal models (ST-ANIMs) at the beginning and at the end of the test period using single-SNP regression in the GCTA software. Results from the genome-wide association studies (GWAS) using TT-REPM and TT-RRM were similar to the conventional approach using the ST-ANIMs. For all models, the variants rs43350564 and rs109326204 presented the strongest association with BW and ADFI, respectively. The identified SNP effects remained constant throughout the feedlot test period and could be useful for understanding the biology of feed efficiency. Further studies with more data and possibly with longer feed lot test periods are needed to investigate the effect of genomic regions for feed efficiency traits over the feedlot trajectory.