Genomic analysis of heterosis in a composite beef cattle breed

Abstract Crossbreeding is widely used in the beef cattle industry to exploit benefits of heterosis. This study evaluated the effects of heterozygosity on growth traits in an Angus x Hereford cross population. Moreover, a genome wide association study was conducted to detect regions in the genome with significant dominance effects on growth traits contributing to heterosis. A total of 1,530 animals, comprised of pure Line 1 Hereford, Angus and Angus x Line 1 Hereford crosses, were evaluated. Phenotypes included birth weight, weaning weight and yearling weight. All animals were genotyped with GeneSeek GGP LD 50k. Effects of genomic heterozygosity on growth traits were estimated. These effects were -0.76 kg (P < 0.001), 4.67 kg (P < 0.0001), 42.39 kg (P < 0.02) on birth weight, weaning weight and yearling weight respectively. A genome wide association study revealed several SNP markers with significant heterotic effects associated with birth weight, weaning weight and yearling weight. These SNP markers were located on chromosomes 1, 2, 14, 19, 13 and 12. Genes in these regions were reported to be involved in growth and other important physiological mechanisms. Our study revealed several regions associated with dominance effects and contributing to heterosis. These results could be beneficial in optimizing crossbreeding.