Vet. Res. 35 (2004) 513-530
DOI: 10.1051/vetres:2004028

Impact of the Salmonella status of market-age pigs and the pre-slaughter process on Salmonella caecal contamination at slaughter

Pierre-Alexandre Beloeil^a, Claire Chauvin^a, Karine Proux^a, François Madec^a, Philippe Fravalo^a and Ahmadou Alioum<sup>b

a</sup>  AFSSA, French Agency for Food Safety, Pig and Poultry Veterinary Research Laboratory, Zoopôle, BP 53, 22440 Ploufragan, France
^b  ISPED, Institut de Santé Publique, d'Épidémiologie et de Développement, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France

(Received 24 November 2003; accepted 20 February 2004)

Abstract - The aim of this study was to evaluate the impact of the pre-slaughter process on Salmonella caecal contamination of pigs at slaughter. An observational study was carried out in 2001 on 101 conventional farrow-to-finish pig farms. On each farm, one batch of contemporary pigs was followed from the end of the fattening period until slaughter. The Salmonella bacteriological status of the batches was assessed by environmental samples of faecal material. The serological Salmonella status was obtained on 30 individually identified market-age pigs using an indirect ELISA test. At the slaughterhouse, 25 g of caecal contents were taken from 10 of the identified pigs. Faecal and caecal material were analysed according to a classical bacteriological method. A questionnaire was designed to obtain information about the type of feeding during the fattening period (dry versus wet), the duration of fasting on the farm before leaving for the slaughterhouse, the duration of transport between the farm and the slaughterhouse, the holding time in lairage at the slaughterhouse and loading and unloading conditions on the farm and at the slaughterhouse. To assess the relationships between these factors and the Salmonella caecal status of the pigs and the batches, two logistic models were fitted at the individual and at the batch level, respectively. The first analysis was performed using a random effects logistic regression model. The second analysis was based on a cumulative logit model with a positive caecal rate classified into three classes as the outcome variable. The results showed that the Salmonella status of market-age pigs assessed on the farm either by serological or bacteriological examinations and the time spent in lairage before slaughtering played a crucial role on caecal contamination. In the light of these results, actions should be considered both on the farm and at the slaughterhouse to decrease the risk of Salmonella contamination of the caecal contents.

Key words: Salmonella / pigs / pre-harvest process / slaughterhouse

Corresponding author: Pierre-Alexandre Beloeil pierre-alexandre.beloeil@agriculture.gouv.fr

© INRA, EDP Sciences 2004