Asymptomatic intestinal carriage of Salmonella in pigs presented for slaughter can result in pork carcass contamination and dietary supplementation with organic acids or their salts is a potential strategy for the control of Salmonella in finishing pigs. The objectives of the present study were to conduct a field study on two selected farms with a high Salmonella seroprevalence, to investigate the ability of dietary supplementation with sodium butyrate during the last month of growth pre-slaughter to: reduce faecal shedding and intestinal carriage of Salmonella, and impact growth performance in finisher pigs. Based on the findings, a cost-benefit analysis was also conducted. Two trials (A and B) were conducted on two commercial farms with high Salmonella seroprevalence. In both trials, pens (14 pens of 12 pigs/pen in Trial A and 12 pens of 12-17 pigs/pen in Trial B) were randomly assigned to a control (finisher feed without additive) or a treatment group (the same feed with 3 kg sodium butyrate/t) for 24-28 days, depending on the trial. Faeces were collected from each pig on days 0, 12 and 24/28, and blood, caecal digesta and ileocaecal/mesenteric lymph nodes were collected from the slaughterhouse. Pigs were weighed at the start and end of the trials, feed intake was recorded, and carcass quality parameters were recorded at slaughter.
At the end of the Trial A, Salmonella shedding was lower for the treatment comparing with control (30% versus 57% probability of detecting Salmonella in faeces, respectively). This reflected the serology results, with detection of a lower seroprevalence in the treatment group (69.5% versus 89%). Differently, no effect on faecal shedding or seroprevalance was observed in Trial B, which may be explained by the detection of a concomitant infection with Lawsonia intracellularis. No differences in Salmonella recovery rates in the caecal digesta or lymph nodes were observed. Furthermore, feed intake, weight gain, and feed conversion efficiency (FCE) did not differ between groups. Numerical improvements in weight gain and FCE were found with sodium butyrate treatment, which gave a cost benefit of €0.04/kg of live-weight gain.
Results suggest that sodium butyrate, at 3 kg/t of feed, to finishing pigs for 24-28 days prior to slaughter was effective in reducing Salmonella shedding and seroprevalance but perhaps only in the absence of co-infection with other pathogens. Nevertheless, sodium butyrate supplementation at this rate did not affect intestinal carriage, nor did it reduce seroprevalence to below the cut-off (50%) used for the high Salmonella risk category in Ireland.
Walia, K., Argüello, H., Lynch, H., Leonard, F. C., Grant, J., Yearsley, D., Kelly, S., Duffy, G., and Gardiner, E.G., (2016). Effect of feeding sodium butyrate in the late finishing period on Salmonella carriage, seroprevalence, and growth of finishing pigs. Preventive veterinary medicine, 131, 79-86. https://doi.org/10.1016/j.prevetmed.2016.07.009