Interventions to reduce non-typhoidal Salmonella in pigs during transport to slaughter and lairage: Systematic review, meta-analysis, and research synthesis based infection models in support of assessment of effectiveness

The only intervention captured by the review which was significantly associated with reduced risk of Salmonella in field settings, was elimination of lairage, which is not currently feasible commercially. The logistic regression model for fecal Salmonella shedding in pigs with a random intercept for trial yielded the following predictors significantly associated with increased odds of infection: oral challenge route relative to intra-nasal, log increase in challenge dose, and elapsed time post-challenge. Univariable exact logistic regression modeling lymph node contamination post-challenge yielded the following predictors significantly associated with increased odds of Salmonella infection: younger animals relative to older ones; intra-nasal challenge route relative to oral route; and animals sampled within the first 7 days post-challenge relative to those sampled at 14 or 21 days. We hypothesize that the presence of absence of one or more of these predictors across studies could help to explain the inconsistent and/or non-significant findings reported for some interventions applied at lairage.