GENOME-WIDE ASSOCIATION STUDY OF WEANING TRAITS IN LORI-BAKHTIARI SHEEP

Weaning traits, including preweaning daily gain (PWDG) and weaning weight (WW) are important economic traits, especially for meat type mammals, with high impacts on growth performance and survival rate in higher ages. This study was conducted to perform a genome-wide association study (GWAS) on weaning traits in a meat type breed of sheep. Body weight records of 7557 Lori-Bakhtiaii sheep with PWDG and WW records were used to estimate breeding values (EBVs) using an animal mixed model. A total of 132 animals were selected by two-tailed selection strategy, based on EBVs for body weight and then were genotyped using Illumina 50k Ovine SNP chip. After quality control, a total of 130 animals and 41323 SNPs remained for further analyses. De-regressed estimates of breeding values were used as a pseudo-phenotype in GWAS analysis. Based on Bonferroni-adjusted P-values, five SNPs, located on chromosomes 2, 3, 4, 12 and 22 were significantly (P<0.05) associated with weaning traits and accounted for 5.06% and 0.37% of total genetic variations of PWDG and WW, respectively. Two SNPs on chromosomes 2 and 3 were located near to previously reported QTLs for weaning traits. Three genes, including ANGPTL7, mTOR and WDR11, were found within 50 kbp distances from the significant SNPs and thus could be considered as candidate genes for weaning traits. The detected QTLs and candidate genes could be studied for construction of breeding programs for genetic improvement of growth performance in meat type sheep.