Effect of time in lairage on caecal and carcass salmonella contamination of slaughter pigs.

A longitudinal study of the effect of time spent in lairage on salmonellas in the caecum and on the skin surface of 450 slaughter pigs from a single producer was conducted. Pigs were tested in 6 groups at 2 abattoirs, with one-third of a group being slaughtered after 18 h, one-third after 42 h and one-third after 66 h spent in lairage. The salmonella isolation rate from caeca and carcass surfaces increased significantly with increasing time spent in lairage. Salmonellas were isolated from the caeca of 18.5% of pigs held less than 24 h in lairage, 24.1% of pigs held a further 24 h and 47.7% of pigs held for 66 h in lairage before slaughter. The salmonella isolation rates from carcasses were 9.3%, 12.8% and 27.3% for the same groups. Thirteen salmonella serotypes were isolated from the caecal contents and carcasses over the 6 weeks of the trial. One abattoir had a higher salmonella isolation rate from pigs than the other and this was probably related to lairage management. It appeared that lairage is an important factor in the manipulation of the salmonella contamination of pig carcasses.