Does Pre-Slaughter Transportation and Lairage Affect Salmonella Enterica Shedding Frequency and Levels in Market Pigs?

Approach: This research will be conducted under commercial conditions (i.e., field study), where multiple lots of finishing pigs will be sampled during the early grow-finish stage to identify 6 Salmonella-positive lots to be used in this project. Salmonella-positive lots will be sampled again twice to determine common on-farm Salmonella shedding levels, and to identify pens with positive pigs that will be the source of randomly selected animals (N=30 pigs per lot) at the end of the finishing production stage. These animals will be individually identified and sampled as they are moved to be loaded for transportation. To eliminate the chance of contamination/infection of pigs from the transport trailer, a clean and disinfected trailer will be used. Pigs will be transported for approximately 2 hours to a commercial abattoir. During the process of unloading the pigs at the abattoir, individual samples will again be collected, and the animals will be moved to a conventional pre-slaughter resting (i.e., lairage) pen. After approximately 2 hours of resting, individual samples will be collected. In the laboratory, samples will be processed for the isolation and quantification of Salmonella enterica, and for enumeration of total Enterobacteriaceae. The experimental design applied in this research is based on individually paired samples (i.e., individually matched fecal samples collected at different time points; pre-transportation, post-transportation, and post-lairage). Qualitative data (i.e., prevalence or frequency) will be analyzed by comparison of proportions using McNemar?s Chi-square test, whereas quantitative data (i. e., levels or counts) will be transformed to units of log10 CFU/g, and subjected to an analysis of variance. All statistical inferences will be based on P<0.05.