Submitted to: International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork
Publication Type: Proceedings
Publication Acceptance Date: August 10, 2009
Publication Date: September 30, 2009
Citation: Anderson, R.C., Krueger, N.A., Genovese, K.J., Stanton, T.B., MacKinnon, K.M., Harvey, R.B., Callaway, T.R., Edrington, T.S., Nisbet, D.J. 2009. Effect of thymol or diphenyliodonium chloride on feed intake, average daily gain and gut Campylobacter concentrations in growing swine. Proceedings of International Symposium on the Epidemiology and Control of Foodborne Pathogens in Pork. p. 246-249. Interpretive Summary: Pigs can harbor the food-poising bacterium, Campylobacter, in their gastrointestinal tract. Consequently, farmers and processors are interested in finding ways to reduce contamination of pigs by this bacterium. Campylobacter differ from most other beneficial gut bacteria in that they do not metabolize carbohydrates but can utilize amino acids as a major energy-yielding nutrient. We have found in earlier laboratory studies that if the process of degrading amino acids is inhibited by the chemicals thymol and diphenyliodonium chloride (DIC), then Campylobacter do not survive. To test if these chemicals could be fed to pigs to kill Campylobacter, we fed growing pigs diets supplemented with or without thymol or DIC. We found that average daily feed intake and average daily gain were not affected by the chemical supplements, indicating that the pigs did not mind the taste and that they performed equally well when fed the chemicals. Numbers of Campylobacter in feces collected from pigs fed thymol or DIC were approximately 10-fold lower than in feces collected from control pigs, indicating that thymol and DIC may work well to reduce these bacteria in growing pigs. However, measurement of digestion endproducts in the gut contents suggested that appreciable amounts of thymol and DIC may have been absorbed. These results indicate that better feeding strategies will need to be developed in order to optimize the Campylobacter-controlling effect of these chemicals. Ultimately, these results will help farmers and processors find new and more economical methods to grow and produce healthy, nutritious, and safe pork products at less cost for the American consumer.
Technical Abstract: Food-producing animals can be reservoirs of Campylobacter, a leading bacterial cause of human foodborne illness. Campylobacter differ from most other gut bacteria in that they do not ferment carbohydrates but can utilize amino acids as major energy substrates, a process that can be inhibited by thymol and diphenyliodonium chloride (DIC). To evaluate palatability issues pertaining to feeding thymol or DIC, growing pigs were provided ad libitum access to standard growing diets supplemented with or without 0.0067% or 0.0201% thymol, or 0.00014% or 0.00042% DIC in a replicated study design (n= 4 pens per treatment per replicate, 2 pigs/pen). The diets were offered 2X/day for 7 days, during which time average daily feed intake (2.39 ± 0.06 kg d**-1; mean ± SEM) and average daily gain (0.62 ± 0.04 kg d**-1) were not affected (P > 0.05) by treatment. A trend was observed (P = 0.07) for the 3X levels of thymol and DIC to reduce rectal Campylobacter concentrations (5.2 versus 4.2 and 4.4 log10 CFU g**-1 contents for controls and thymol or DIC, respectively; SEM = 0.26). However, no effect (P > 0.05) of treatment was observed on ileal or cecal Campylobacter (1.6 ± 0.17 and 4.5 ± 0.26 log10 CFU g**-1, respectively) or on cecal total cultureable anaerobes (9.8 ± 0.10 log10 CFU g**-1). Moreover, treatment effects were not observed (P > 0.05) on accumulations of the major fermentation end products within collected gut contents. These results suggest that appreciable quantities of thymol and DIC were absorbed or degraded in the proximal alimentary tract and that encapsulation technologies will be needed to deliver effective concentrations of these compounds to the lower gut to achieve in vivo efficacy against Campylobacter.