Genome-wide association study for Kleiber ratio and growth efficiency traits in Lori-Bakhtiari sheep.

Genome-wide association study (GWAS) is a useful method for identification of the genomic regions associated with the studied traits, which could be used in marker-assisted selection. Finding genomic regions and biological pathways for growth efficiency and Kleiber ratio, as important indices of growth rate, may play noticeable roles in genetic improvement of growth performance in meat-type animals. This study was conducted for determination of genomic regions and candidate genes associated with growth efficiency and Kleiber ratio traits in Lori-Bakhtiari sheep, a heavy meat-type sheep. Blood samples of 132 healthy sheep in a research flock were used for DNA extraction. The samples were genotyped using the Illumina ovine 50 K SNP chip. GWAS was done using the Plink software. In the model used for the analysis, birth year-season, sex, birth type and dam age were fitted as the fixed factors. The first 5 principal components were also fitted as covariates to account for possible population stratification. The studied traits had low estimates of genomic heritability. In GWAS, a total of eight SNPs, located on ovine chromosomes 1, 3, 7, 14, 17 and 24 had suggestive significant associations (genome-wide p < [Formula: see text]) with the studied traits. Based on post-GWAS investigations, GCAT, SRP19, APC, EPB41L4A, GPT2, CRYBB3. U6 and 5S rRNA can be considered as candidate genes for growth efficiency traits. The results of this study showed that growth efficiency traits probably cannot be easily improved by selection on estimates of breeding values, but their genetic improvement can be boosted by use of genomic information.