Inspection of lymph nodes for caseous lymphadenitis and its effect on the density of microbes on sheep carcasses

This study aimed to measure the amount of microbial contamination caused by inspecting the lymph nodes of adult sheep carcasses for caseous lymphadenitis (CLA). Surface swabs from carcasses pre-inspection (N=296) and post-inspection (N=296) were obtained for enumeration of indicator organisms at three commercial abattoirs. At the scapular site, inspection doubled the probability of detecting E. coli (Pr before=0.35, Pr after=0.67) and increased the expected count of E. coli from 2cfu/cm2 to 13cfu/cm2. Inspection at the rump site increased the probability of detecting E. coli by 1.1 times (Pr before=0.84, Pr after=0.93) and increased the expected count from 32cfu/cm2 to 45cfu/cm2. Effects were also observed for Enterobacteriaceae and total viable count. The findings show that routine inspection of adult sheep carcasses for CLA has a detrimental impact on carcass microbiological traits. ► Sheep carcasses are inspected for caseous lymphadenitis (CLA) at slaughter. ► Changes in microbiology of carcass surfaces due to inspection were assessed. ► A consistent elevation in counts of three different indicator organisms was observed. ► Inspection for CLA may be counterproductive from a hygiene perspective.