Analysis of Candidate Genes for Growth and Milk Performance Traits in the Egyptian Barki Sheep

SIMPLE SUMMARY: The Barki sheep breed is one of the main sheep breeds in Egypt, and it is well adapted to the harsh desert conditions in the Mediterranean zone. Growth performance has an important role regarding the supply of red meat for human consumption. In addition, milk production is very important to adequately feed newborn lambs and prevent them from starvation. In this study, segregating single nucleotide polymorphisms (SNP) were identified in the coding regions of eight candidate genes for growth and milk traits by direct sequencing. Subsequently, a population of Barki ewes and lambs was screened for these SNPs, and associations between genotypes and traits of interest were assessed. Out of the candidate genes, SNPs of LEP, STAT5A, PRL, and GHRHR were significantly associated with phenotypes. This study provides first insights into the genetics of milk and growth traits in the Barki sheep. The findings concluded that LEP, STAT5A, PRL, and GHRHR might be regarded as candidate genes to improve the Egyptian Barki sheep breed. ABSTRACT: The most common sheep breeds of Egypt are Ossimi, Rahmani, and Barki breeds. The latter one is well adapted to the challenging desert environment, characterized by food shortage and a high temperature fluctuation. Growth performance of Barki sheep has an important economic value in terms of minimizing the shortage of mutton meat in Egypt. Further, milk production is of great importance for feeding newborn lambs. Eight candidate genes, recently associated with production traits in different breeds, were used to study the effect of genotype on lamb growth and ewe milk traits. The examined genes were LEP, IGF1, DGAT1, STAT5A, PRL, CSN1S2, GHR, and GHRHR, of which one representative single nucleotide polymorphism (SNP) located in the coding region was selected for genotyping. Data from 251 Barki sheep were used in this study. Association analysis between SNPs and lamb growth traits identified rs420693815 of the LEP gene to be significantly associated with weaning weight and average daily gain. In ewes, significant effects on milk yield and composition have been estimated for LEP (rs420693815), STAT5A (rs161082816), PRL (rs422713690), and GHRHR (rs414991449). The results indicated that these genes might be considered as interesting candidates for further investigations to improve growth and milk performance in Barki sheep.