Submitted to: Journal of Animal Science
Publication Type: Proceedings
Publication Acceptance Date: April 30, 2005
Publication Date: June 20, 2005
Citation: Edrington, T.S., Genovese, K.J., Schultz, C.L., Callaway, T.R., McReynolds, J.L., Anderson, R.C., Nisbet, D.J. 2005. Effects of feed intake, stress or exogenous hormones on Salmonella enterica serovar choleraesuis in pigs. Proceedings of Western Section of the American Society of Animal Science. 56:226-229. Interpretive Summary: Stress, a common problem in pig production, may increase populations of the bacteria Salmonella in these animals. Salmonella is important because it can make pigs sick and also people who eat pork that is contaminated with Salmonella. Additionally, pigs produce hormones that bacteria may use for growth and survival. The purpose of these studies was to determine if stress or selected hormones had any effect on Salmonella in weaned pigs. Results showed that stress did increase populations of Salmonella while hormone administration had very little effect.
Technical Abstract: Two experiments were conducted to examine the role of feed restriction (FR), stress (STR), or exogenous hormones on Salmonella colonization in pigs. Thirty pigs (avg. BW = 13.5 kg) were randomly assigned to pen (2 pigs/pen) and treatment: control (CON, 3 pens); FR (4 pens); STR (daily co-mingling, 4 pens) and FR+STR (4 pens). On d 1, all pigs were inoculated with S. enterica serovar choleraesuis and treatments initiated. Fecal samples, feed intake, scour and activity scores were collected daily and on d 6 pigs euthanized and gut tissue and luminal contents collected along with ileo-cecal lymph nodes, spleen and liver tissue. Treatment had no effect (P > 0.10) on daily fecal shedding of Salmonella averaging 2.26, 1.98, 1.74, and 1.89 CFU (log10/g feces) across the experimental period for CON, FR, STR,and FR+STR treatments, respectively. Compared to CON, STR decreased (P < 0.01) Salmonella in cecal (1.85 vs 3.79) and tended to decrease (P < 0.10) counts in colon (1.80 vs 2.98) and ileal (4.0 vs 5.33) contents. The number of Salmonella positive lymph nodes was doubled (P < 0.05) in all treatments compared to CON, while FR and FR+STR tended to increase the number of positive stomach tissue samples. In a second experiment, 28 pigs (avg. BW = 10.6 kg) were assigned to treatment (7 pigs/treatment): CON; melatonin (MEL, 1.3 mg/kg BW); serotonin (SER, 0.5 mg/kg BW); or tryptophan (TRP, 0.2 g/kg BW). Pigs were dosed daily for 9 days, inoculated with Choleraesuis on d 6, and euthanized on d 9 for sample collection as described above. Treatment had no affect (P > 0.10) on daily fecal shedding. The SER treatment numerically increased (P = 0.15) populations of Salmonella in the colon contents and increased (P < 0.01) the number of Salmonella positive spleen samples. These results support the hypothesis that stress and/or hormones may play a role in the colonization and pathogenicity of Salmonella in swine.