Genomics of seasonal hair shedding and ecoregion-specific growth to identify environmentally-adapted beef cattle
Recently, interest has increased in augmenting current national scale cattle evaluations with precision genetic predictions tailored to specific environmental conditions. Some efforts to develop environmentally-aware predictions have focused on the use of novel phenotypes and others on the incorporation of genotype-by-environment interactions (GxE) to existing methodologies. Cattle and other mammal species molt thick winter coats at the beginning of summer in order to prepare for the oncoming stress of warmer weather. In warm climates, cattle that shed their winter coat earlier and more completely have an adaptive advantage over later-shedding herd-mates, and previous work has demonstrated the relationship between seasonal coat shedding and production traits. Using a novel trait (early summer hair shedding score) we develop a genetic evaluation for heat tolerance. We find that hair shedding score is moderately heritable and controlled by genomic loci involved in light sensing and metabolism. Additionally, we explore the degree to which GxE interactions across discrete ecoregions affect pre-weaning growth in American Angus cattle. We find evidence for GxE in the maternal but not direct effect of weaning weight, particularly in heat-stressed environments. Together, these efforts will help beef cattle breeders match genetics to the environmental conditions in which they are best suited.
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