A Simple Assay to Assess Salmonella Typhimurium Impact on Performance and Immune Status of Growing Pigs after Different Inoculation Doses.

Salmonella Typhimurium is the most frequent serovar in pigs and causes infections in humans. However, the dosage used for experimentation is not well defined. The present study aimed to evaluate a dosage for oral inoculation with Salmonella Typhimurium to assess immunological and growth performance alterations in pigs. Gilts were randomly allocated into one of three experimental treatments: no Salmonella Typhimurium inoculation (Basal), or oral inoculation of 1 × 10 8 or 1.5 × 10 8 colony-forming units of Salmonella Typhimurium. Growth rate, rectal temperature, and fecal Salmonella shedding were recorded. Blood samples were taken. Inoculated pigs shed the bacteria for up to 7 days, but no differences were observed between the groups. No differences were observed in rectal temperature, body weight, or average daily feed intake. However, reductions in average daily gain (-17 and -22%) and feed efficiency (-14 and -20%) were observed in pigs inoculated with 1 × 10 8 and 1.5 × 10 8 colony-forming units, respectively. The hemoglobin and hematocrit concentrations increased in challenged pigs compared to Basal pigs. The oral dosage of 1.5 × 10 8 colony-forming units of Salmonella Typhimurium is suitable for activating the immune system of pigs and assessing the impact of Salmonella on pig performance.