Genome-wide association study of growth and body composition traits in Brangus beef cattle

• 18 significant QTL were identified associated with growth and body composition traits in Brangus.
• 7 QTL had pleiotropic effects, in which 4 of them were novel.
• 11 QTL were trait-specific, in which 2 were novel.

The availability of high-density single nucleotide polymorphism (SNP) genotypes, such as BoveineHD770K, provides opportunities to identify genomic regions associated with traits in cattle. The objective of this study was to identify quantitative trait loci (QTL) associated with growth and body composition traits in Brangus beef cattle using actual and imputed 770 K SNP genotypes. A total of 1537 Brangus beef cattle were genotyped with the Bovine50K, GGPHD77K, or BovineHD770K SNP chip and deregressed estimated breeding values were derived and fitted as observations in analyses. BayesB approach was used to map QTL for each trait, and significant windows and SNPs were identified. A total of 18 QTL were identified, in which 7 were associated with more than one trait, while the remained 11 QTL were trait-specific. One pleiotropic QTL of particularly large-effect was identified on chromosome 6 at 38 Mb, which influences direct birth weight, weaning weight, and yearling weight, and harbors growth-related genes NCAPG and LCORL. Biological pathways of pleiotropic QTL were also performed using gene ontology term enrichment analysis. The QTL mapping results obtained from this study will aid in better understanding the biological processes accounting for variation in growth and body composition traits in Brangus cattle.