Targeted low cost strategies to combat Salmonella spp. in finisher pigs and in the slaughterhouse

Salmonella carriage in pigs is a significant food safety issue and low-cost control measures may provide a useful element in reducing the prevalence of Salmonella in pigs. This thesis aimed to investigate several pre-harvest Salmonella control strategies directed towards finishing pigs (35-110 kg). At farm level, two strategies focusing on dietary supplementation with feed additives: (1) sodium butyrate; and (2) an encapsulated blend of formic acid, citric acid, and essential oils (FormaXOL™) were investigated for their effectiveness to control Salmonella shedding and seroprevalence in pigs 28- and 63-days prior to slaughter. In the abattoir, two strategies: (3) cleaning and disinfection (C&D) of lairage pens with a quaternary ammonium chloride or chlorocresol-based disinfectant; and (4) misting pigs with a preoxygen disinfectant at 0.5% were evaluated for their ability to eliminate Salmonella in the lairage environment and to topically reduce Salmonella prior to slaughter, respectively. Supplementation with sodium butyrate and FormaXOL™ for 28-days prior to slaughter, not 63-days (for sodium butyrate only), was effective in reducing Salmonella shedding and seroprevalence but only in the absence of secondary infections. Both feed additives did not influence intestinal carriage, nor did they reduce seroprevalence to below the cut-off used for the high Salmonella risk category in Ireland (50%), or significantly improve growth performance. Treatment with sodium butyrate provided a benefit of €0.04/kg of live-weight gain; while supplementation with FormaXOL™ increased the feed cost/kg of live-weight gain by €0.08. In the abattoir, drying lairage pens after C&D with a chlorocresol-based disinfectant eliminated Salmonella. Additionally, misting with a preoxygen disinfectant might have a role in topical antisepsis for pigs contaminated with Salmonella prior to slaughter and as such warrants further investigation. The findings presented herein, are readily applicable to farmers, abattoirs and regulatory agencies; and have added novel findings to the field of Salmonella control in pigs.