Genomic Analysis of Heterosis in an Angus × Hereford Cattle Population

SIMPLE SUMMARY: Crossbreeding is commonly practiced in the US. Traditionally, it has been used to improve performance by mating animals from different breeds to benefit from heterosis and complementarity (i.e., the general tendency for crossbred offspring to have superior performance compared to those of the parents). With the advent of genomic information, we are now able to dissect heterosis on a molecular level. In this study, we evaluated the effects of heterozygosity on growth traits in an Angus × Hereford cross-population and identified regions in the genome associated with heterosis. The effects of crossbreeding were an increase of 0.03 kg, 5.13 kg, 6.02 kg in birth weight, weaning weight and yearling weight, respectively. Moreover, regions in the genome having significant effects related to heterosis were associated with birth weight, weaning weight and yearling weight and were located on chromosomes 1, 2, 6, 21, 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. ABSTRACT: Crossbreeding is widely used in the beef cattle industry to exploit its several benefits. This study evaluated the effects of heterozygosity on growth traits in an Angus × 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 1530 animals comprising of pure Line 1 Hereford, Angus and Angus × Line 1 Hereford cross. Growth phenotypes included birth weight, weaning weight and yearling weight. All animals were genotyped with GeneSeek GGP LD 50k. Significant effects of genomic heterozygosity on growth traits were detected. These effects were 0.03 kg (0.006), 5.13 kg (0.04), 6.02 kg (0.08) on birth weight, weaning weight and yearling weight, respectively. 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, 6, 21, 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.