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It is well known that infections by enterotoxigenic Escherichia coli F4 (ETEC) bacteria cause high economical loses in pig production. ETEC uses specific bacterial adhesion factors, such F4 fimbriae and produce heat-labile toxin (LT). Some commercial plant derived polyphenol extracts can inactivate heat labile toxin (LT) of ETEC in vitro, whereas others do not, but it is not known whether these polyphenols have the same properties in vivo.
In this study, a total of fourty 21d-old just weaned piglets were housed in eight pens with five piglets per pen. Animals were tested pre-infection for absence of ETEC. Three extracts (A; high molecular weight hydrolysable tannins; B; an extract from grape seeds and C; a polyphenol extract from cocoa beans) were added to feed and tested for in vivo efficacy in a post-weaning diarrhoea 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. On days 6 and 7 after the start, twenty animals received 5 ml ETEC suspension of 109 CFU/ml by oral gavage, the other twenty received vehicle only (5 ml PBS). Post-infection, rectal faeces were daily assessed for diarrhoea (as % faecal 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 B (p<0.004). Diarrhoea was abolished by B and A, but not by C. No differences were found for ADG, ADFI, and FCR, except for C which depressed ADG post-infection significantly (p<0.005). The latter suggests C 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 diarrhoea most likely by inactivating LT in vivo.
Verhelst, R., Schroyen, M., Buys, N. and Niewold, T. (2014). Dietary polyphenols reduce diarrhea in enterotoxigenic Escherichia coli (ETEC) infected post-weaning piglets. Livestock Science 160:138-140. doi:10.1016/j.livsci.2013.11.026