Variation of bacteriologic and serologic Salmonella enterica prevalence between cohorts within finishing swine production farms

The objective of this study was to evaluate the consistency of bacteriologic and serologic Salmonella enterica prevalence in cohorts of finishing pig lots from multiple production farms. A total of 6 lots of finishing pigs from each of 6 finishing production farms were included in this study. For each lot studied, 30 individual fecal samples were collected directly from the rectum immediately before the pigs were transported to the abattoir, and 50 individual meat samples were collected at slaughter. Individual fecal and meat juice samples were processed for detection of Salmonella and antibodies against Salmonella, respectively. All finishing production farms were Salmonella-positive in at least 2 fecal and 4 meat samplings. The overall bacteriologic prevalence was 12.9% (95% C.I. 8.0–17.8%), whereas the serologic prevalence was 35.4% (95% C.I. 24.5–46.4%; P < 0.05). A wide variation in Salmonella prevalence (bacteriologic and serologic) between different finishing pig lots within production farms was observed, preventing the categorization of the production farms as either high or low Salmonella prevalence. This study shows that bacteriologic and serologic estimates of Salmonella prevalence are not consistent among cohorts within the same production farm, suggesting that point estimates of Salmonella prevalence in swine populations are not reliable.