Genome-wide association study of birth weight in sheep

Birth weight is the earliest available growth trait with considerable impacts on lamb survivability and growth performance traits. This study was conducted to perform a genome-wide association study of birth weight in a meat-type sheep. A total of 132 Lori-Bakhtiari sheep were selected based on estimated of breeding values (EBVs) for BW analyses. The selected animals were genotyped using Illumina Ovine SNP50 Bead Chip. After quality control, a total of 41 323 single-nucleotide polymorphisms (SNPs) and 130 sheep were used for subsequent analyses. Plink 1.90 beta software was used for the analyses. Seven SNPs on chromosomes 1, 16, 19 and 22 were detected based on genome-wide unadjusted P-values (P <10-6), which jointly accounted for 1.2% of total genetic variation. However, based on Bonferroni-adjusted P-values, only three SNPs on chromosome 1 had significant associations with EBVs for birth weight (P <0.05), which jointly explained 0.8% of total genetic variation. A total of seven genes were found in 50 kb intervals from the three significant SNPs on chromosome 1, but only three genes, including RAB6B (a member of RAS oncogene family), Tf serotransferrin and GIGYF2 (a GRB10 interacting GYF protein 2), could be considered as candidate genes for birth weight in future studies. The results of this study may facilitate potential use of the genes involving in growth and production traits for genetic improvement of productivity in sheep.