Location: Food and Feed Safety Research
Title: Effect of thymol or diphenyliodonium chloride on performance, gut fermentation characteristics, and campylobacter colonization in growing swine Authors
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 14, 2011
Publication Date: April 1, 2012
Citation: Anderson, R.C., Krueger, N.A., Genovese, K.J., Stanton, T.B., MacKinnon, K.M., Harvey, R.B., Edrington, T.S., Callaway, T.R., Nisbet, D.J. 2012. Effect of thymol or diphenyliodonium chloride on performance, gut fermentation characteristics, and Campylobacter colonization in growing swine. Journal of Food Protection. 75:758-761. Interpretive Summary: Pigs can harbor in their gastrointestinal tract an important food-poisoning bacterium called Campylobacter. This bacterium can contaminate food produced for human consumption during processing. Consequently, farmers and processors are interested in finding ways to reduce contamination of pigs by this bacterium. Campylobacter differs 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 the Camylobacter are not able to 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 Camylobacter 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 not 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 worldwide. Unlike most other gut bacteria, Campylobacter do not ferment carbohydrates but can utilize amino acids as major carbon and energy substrates, a process that can be inhibited by thymol and diphenyliodonium chloride (DIC). In order to determine the effect of these potential additives on feed intake, live weight gain, and gut Campylobacter concentrations, growing pigs were fed 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 per pen). The diets were offered ad libitum twice daily for 78 days during which time average daily intake (2.39 ± 0.06 kg d-1) were not affected (P > 0.05) by treatment. Pigs treated with DIC, but not thymol, tended (P = 0.07) to have lower rectal Camylobacter concentrations (5.2 versus 4.2 and 4.4 log10 CFU g-1, respectively) or on cecal total cultureable anaerobes (9.8 ± 0.10 log10 CFU g-1). Moreover, effects of treatment were not observed (P > 0.05) on accumulations of the major fermentation end products within collected gut contents. These results suggest that thymol and DIC were appreciably absorbed or degraded in the proximal alimentary tract and that encapsulation technologies will likely be needed to deliver effective concentrations of these compounds to the lower gut to achieve in vivo reductions of Camylobacter.