38 Effect of Breed Composition and Genome-Wide Association Study on Epidermis Thickness in a Multibreed Angus-Brahman Population

Heat stress in cattle has recently received growing attention because of anticipated increases in environmental temperature by global warming. Heat stress limits the production efficiency of cattle, and it is one of the principal causes of economic loss for beef cattle producers in these environments. Thermotolerance can be defined as the ability to maintain optimal growth, feed intake, and reproduction under the presence of heat stress, and it varies among individual animals and breeds. The objectives of the analysis were to investigate the amount of variation on epidermis thickness, test the effect of breed composition and age group on skin histology traits and to conduct a genome-wide association study on skin properties of beef cattle, focusing on the epidermis thickness. Skin biopsy samples were collected from 318 heifers from a UF multibreed population (animals ranging from 100% Brahman to 100% Angus), genotyped with the Bovine GGP F250K chip. Quality control was conducted with BLUPF90 software, including a call rate of 0.90 and a MAF < 0.01. BLUPF90 software was used to fit a single locus mixed model to test the effect of each marker. Breed group and age group were included as fixed effects. There is a significant effect in breed group ((P < 0.0001) and in age group (P < 0.0001). This study shows there is a large amount of variation in epidermis thickness across and within breed groups. Significant SNPs for the thickness of the epidermis were found in the HBEGF gene, which is a protein coding involved in several processes, including epidermal growth factor receptor signaling pathway and there is a variation across breed Skin histology traits are fundamental for the ability to lose heat more efficiently and allow the maintenance of normal body temperatures under extreme conditions. This study could contribute toward improving cattle’s adaptation to thermal stress.