Effect of enzyme resistant starch on large bowel fermentation in rats and pigs

Abstract

The effect of raw and retrograded high-amylose corn starch, added to a semisynthetic or conventional diet, on the fermentation process in the cecum of the rat and in the proximal colon of the pig was investigated. A trophic effect on the rat cecal wall was observed when both types of diets were fed. Moreover, lower pH values were noted in rats as well as in pigs. There was no general inverse relation between cecal or colonic pH and L-lactic acid concentrations. Rats fed the enzyme resistant starch sources had significantly lower cecal ammonia concentrations, indicating higher bacterial activity resulting in increased conversion of ammonia to bacterial protein. A similar, however non-significant (P=0.06) effect was found in pigs. Generally, the mean cecal concentrations of volatile fatty acids were higher upon resistant starch feeding to rats given semi-synthetic diets, but the effects were only significant for butyrate and total volatile acid concentration when retrograded high-amylose corn starch was supplied. On the contrary, rats receiving resistant starch added to the conventional diet showed no significant influences on cecal butyric acid and total volatile fatty acid concentrations. Also in pigs, no significant effects of enzyme resistant starch intake on colonic volatile fatty acid concentrations were found. No significant effects of enzyme resistant starch intake on portal blood volatile fatty acid concentrations were observed in rats. In general, the amount of butyric acid as part of the total volatile acids was substantially lower in the portal blood as compared with the cecum, suggesting that butyric acid was greatly metabolized by the intestinal wall.