Effect of Pre-slaughter Feed Restriction on Bacterial Numbers in the Stomach and Caecum of Pigs

F.M. Nattress, R. J. Worobo and A.C. Murray

Agriculture & Agri-Food Canada Research Centre, 6000 C & E Trail, Lacombe, AB Canada, T4L 1W1

The microbiological condition of carcasses is a major concern to the meat packing industry, with the identification of critical control points during slaughter and dressing comprising an important aspect of improvement in processing practices. Holding pigs off feed overnight prior to slaughter is preferred by meat packers because the incidence of PSE pork is reduced. Gut fill is also reduced with the assumption that microbial contamination of carcasses will similarly be reduced.

Three regimes of ante-mortem management were examined to determine their effects on the numbers of lactic acid bacteria, coliforms and E. coli in the stomach and caecum of hogs immediately after slaughter: 1. Pigs had access to food until transported to the abattoir where they were slaughtered after 0, 2, 4 and 24.5 h in lairage; 2. Pigs were transported to the abattoir, were held in lairage overnight without access to feed and were slaughtered 18, 20 and 22 h after their last offering of food; 3. Feed was withdrawn from pigs 15 h before transport to the abattoir and they were slaughtered after 0, 2 and 4 h in lairage.

In general, bacterial numbers decreased in the stomach and increased in the caecum. Changes in numbers of coliforms and E. coli were most pronounced when feed was withdrawn 15 h prior to transport. Thus the proportion of coliforms that were E. coli rose from 59% to 94%. In the caecum E. coli numbers increased by 1.2 log units as a result of withdrawal of feed 15 h prior to transport and continued to increase during lairage.

Implication. The numbers of E. coli and possibly other pathogens in the caecum of pigs can be increased as a result of feed withdrawal. Removal of feed 18 to 22 h prior to slaughter resulted in a 17 fold increase in E. coli if the animals were transported after feed withdrawal. This may be reflected in increases in E. coli on the carcass.