Risk factors associated with Salmonella enterica prevalence in three-site swine production systems in North Carolina, USA

The goal of this study was to identify risk factors associated with increased fecal shedding of Salmonella enterica (SE) in groups of market swine reared in large three-site production units. We conducted an intensive, long-term investigation of potential management and environmental risk factors operating during the growing phase of pig production. Data regarding finisher site characteristics, biosecurity protocols, group growth performance, medication usage, and environmental temperature were collected. Results indicate that SE infection is common. Risk factors were identified at both the finisher site and group level. Biosecurity and hygiene practices (absence of a toilet, more than 2 people present at a finisher site daily, and other domestic species at the site), environmental temperature (winter and spring seasons, increased temperature variability, and below median high temperature the day of sampling), and production performance (above median feed conversion) were associated with elevated SE prevalence. In addition, an association between the floor space allowances per pig at the time of sampling (a measure of the number of pigs sold prior to sampling) was identified, with greater space allowance associated with decreased prevalence. The results of this study identify potential management practices for evaluation for SE control and suggest caution in interpretation of fecal culture results when sampling from different marketing groups in swine production systems.