Effect of the addition of protected sodium butyrate to the feed on Salmonella spp. infection dynamics in fattening pigs

Organic acids (OA) are seen as an alternative to antibiotics to reduce the burden of enteropathogens. Two replicates of a field trial were carried out to assess the effect of the addition of protected sodium butyrate (PSB) to the feed (dose of 3 kg/T) along the fattening period on the dynamics of Salmonella spp. infection in pigs. In each trial, around 50 pigs were assigned to a treatment group (TG) and 50 kept as controls (CG). Pigs were serologically monitored monthly and on-farm fecal samples and fecal and mesenteric lymph nodes (MLN) samples at slaughter were collected. In the first replicate, pigs became probably infected with Salmonella before the addition of PSB to the feed, but despite of that an overall lower proportion of shedders along the end of fattening period and lower seroprevalence before slaughter (50% vs. 89.6%; P < 0.001) was observed in the TG. In the second replicate, few pigs shed Salmonella during the trial, which precluded the finding of significant differences between groups for both Salmonella infection and shedding, but the seroprevalence at slaughter in the CG was again significantly higher than in the TG (31.1% vs. 13.7%, respectively; P = 0.02) and it was related to a higher proportion of shedders and MLN-positive pigs. When results from both trials were analyzed together, a significant increasing risk of shedding in the CG was observed at 90 days of fattening and at slaughter, and an overall significant decreasing trend in OD% values and thus in seroprevalence was also observed when pigs approached to slaughter. In conclusion, the dietary administration of this PSB during the whole fattening period was able to reduce significantly the seroprevalence in the TG, which may reflect a positive effect on the control of Salmonella at the end of the fattening period.