Genome-wide association study for milk production of Awassi sheep in Jordan

Genetic selection is an important method to enhance productive traits in local sheep through crossbreeding and selection programs. The objectives of this study were to estimate the genetic parameters of total milk yield (MY) and lactation period (LP), and to investigate the association between the estimated breeding values of milk yield with 50 K SNP chip results in Awassi sheep. Heritability and repeatability estimates were 0.19 and 0.317 for MY and 0.085 and 0.163 for LP, respectively. The Genomic scan covered 42,478 SNPs and revealed two candidate loci (s244475780.1 and s51470.1) that significantly affect milk production, located on Spermatogenesis-Associated Protein6 (SPATA6) and Galactose-3-O-Sulfotransferase 3 (GAL3ST3) genes. The genotype frequencies for the SPATA6 gene variant were 0.0566 for AA, 0.4528 for AG, and 0.4906 for AA, with allele frequency of 0.283 for A and 0.717 for G. The genotype frequencies for the GAL3ST3 gene variants were 0.07843 for TT, 0.4118 for TG, and 0.5098 for GG, with allele frequency of 0.284 for T and 0.716 for G. The two SNPs genotypes are promising biomarkers to increase milk production during genetic selection programs by reducing the frequency of G alleles in the two loci in Awassi sheep genome.