Identification of genomic regions that contribute to wet carcass syndrome in sheep

Abstract

Wet carcass syndrome (WCS), which is observed predominantly in sheep, affects carcass quality negatively. After slaughter the carcass appears to be ‘wet’ with a subcutaneous accumulation of watery fluid. Not all animals in a contemporary group are afflicted, and experimental attempts to induce WCS have been unsuccessful. The reported prevalence of WCS in Dorper and Dorper crosses gave rise to the hypothesis that it may have a genetic basis. Therefore, the primary objective of this investigation was to test this hypothesis using a high-density SNP assay to search loci that may predispose sheep to WCS. Muscle samples from 43 afflicted and 41 unafflicted sheep were collected from slaughterhouses in the province of Northern Cape, South Africa, and in southern Namibia. Tests against candidate genes proved uninformative, as did runs of homozygosity. Potential associations between WCS and an autosomal genetic marker were investigated further in a case-control genome-wide association study. Separate analyses for each sex were motivated because single nucleotide polymorphisms (SNPs) on the X chromosome suggested quantitative trait loci. These analyses revealed significant associations between SNP and WCS in males, but not in females. Three SNPs that reached genome-wide significance in males are in strong linkage disequilibrium with the Duchenne muscular dystrophy, 5-hydroxytryptamine receptor 2C, and Teneurin transmembrane protein 1 genes. These genes are identified as positional candidate genes, and the Duchenne muscular dystrophy, 5-hydroxytryptamine receptor 2C genes have biological effects that have been documented in other species, making them plausible functional candidate genes for WCS in sheep.

Keywords: association analysis, Dorper, sheep carcass, single nucleotide polymorphisms, X chromosome