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

L Van Der Westhuizen,M.D Macneil,M.M Scholtz,F.W.C Neser

doi:10.4314/sajas.v49i5.7

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

Highlights

Wet carcass syndrome (WCS) is a condition that is found predominantly in sheep, which affects the quality of their carcasses negatively
Three single nucleotide polymorphisms (SNPs) on the Ovine Infinium® HD SNP BeadChip were located in the PRKAG3 gene on OAR2, and 25 SNP were located in the ryanodine receptor 1 (RYR1) gene on OAR14 (Van der Westhuizen, 2018)
No other SNP within RYR1 approached significance in affecting the occurrence of WCS and it was concluded that porcine stress syndrome (PSS) and RSE are phenotypically similar to WCS, the current results do not support the hypothesis that mutations in RYR1 or PRKAG3 cause WCS

Summary

Introduction

Wet carcass syndrome (WCS) is a condition that is found predominantly in sheep, which affects the quality of their carcasses negatively. The first incidence of WCS was recorded in January of 1981 at Chambor abattoir in Krugersdorp, Gauteng, South Africa (Jansen, 1991). It is most frequently observed in Dorper and crosses of Dorper with indigenous and locally developed breeds of South Africa and Namibia (Brock et al, 1983; Webb & Van Niekerk, 2011). Afflicted carcasses do not dry off with overnight cooling (Joubert et al, 1985), pose difficulties during meat processing and the meat has a diminished shelf life (Joubert et al, 1985). In South Africa, economic losses that stem from WCS were approximately R27 million in 2010 (Webb & Van Niekerk, 2011; Le Roux, 2012)

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