Dietary polyphenols reduce diarrhea in enterotoxigenic Escherichia coli (ETEC) infected post-weaning piglets

Earlier, we showed that some commercial plant derived polyphenol extracts can inactivate heat labile toxin (LT) of enterotoxigenic Escherichia coli (ETEC) in vitro (Omnivin, and ALSOK), whereas others do not (Omnicoa). In this study, based on 40 three week weaned piglets, these three extracts were added to feed and tested for in vivo efficacy in a post-weaning diarrhea model. Piglets were divided in four treatment groups, and given a control diet or a diet supplemented with 1% of one of the three extracts. Half of each treatment group was infected with ETEC on days 6 and 7 post-weaning. Post-infection, rectal feces was assessed daily for diarrhea (as % fecal dry matter (DM)), ETEC excretion. Average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were determined. Post-infection, ETEC excretion was reduced by all three extracts compared to control feed, and significantly by Omnivin (p<0.004). Diarrhea was abolished by Omnivin and ALSOK, but not by Omnicoa. No differences were found for ADG, ADFI, and FCR, except for Omnicoa which depressed ADG post-infection significantly (p<0.005). The latter suggests Omnicoa to contain an anti-nutritional factor. The overall results for the different polyphenol extracts were consistent with the respective in vitro activities in the LT-inhibition assay. It is concluded that polyphenol extracts do widely differ in properties, some may have deleterious effects, but others can indeed reduce ETEC induced diarrhea most likely by inactivating LT in vivo.