Genome-wide association study of mature cow size traits in American Angus cattle

Mature cow weight (MWT), height (MHT), and body condition score (BCS) are economically important traits that significantly influence cowherd profitability by affecting maintenance feed requirements, which is the largest component of production costs. This study aimed to identify genomic regions, candidate genes, and pleiotropic variants associated with mature cow size traits in American Angus cattle, and to characterize their related gene ontology terms and metabolic pathways. The dataset provided by the American Angus Association comprised 434,746 MWT records from 222,907 animals; 213,875 MHT records from 112,987 animals; and 382,156 BCS records from 209,696 animals. Of these, 45,606 cows were genotyped and imputed to a common marker density of 54,609 markers. A final dataset of 51,410 SNPs from 45,452 animals remained after quality control for further analyses. The single-step genome-wide association study (ssGWAS) method was used in the analyses. Significant associations for mature cow size were detected on BTA7, BTA14, and BTA20, overlapping with previously reported QTLs for growth, feed efficiency, and carcass traits. Candidate genes such as FBXO32, STC2, DUSP1, CREBRF, LAP3, and PENK were found to be related to muscle development, skeletal growth, lipid metabolism, and energy regulation. The genes FBXO32, NTAQ1, ATAD2, DUSP1, ERGIC1, RPL26L1, ATP6V0E1, CREBRF, BNIP1, NKX2-5, and STC2 emerged as candidate genes exhibiting pleiotropic effects on mature cow size traits. Pathway enrichment highlighted the roles of insulin/IGF1R signaling, fibroblast growth factor receptors cascades, and mitogen-activated protein kinase pathways in MWT and MHT, while for BCS, only RHOD GTPase cycle was enriched. Pleiotropy-based analysis of regions affecting mature cow size traits identified shared genomic loci, and subsequent pathway analysis revealed G protein signaling as a common regulatory mechanism linking energy balance, adiposity, and growth. These results contribute to a better understanding of the genomic regions associated with mature cow size traits in Angus cattle.