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

The effect of raw and retrograded high-amylose corn starch, added to a semi synthetic 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 e ffect 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 significan tly lower cecal ammonia concentrations, indicating higher bacterial activit y resulting in increased conversion of ammonia to bacterial protein. A simi lar, however non-significant (P=0.06) effect was found in pigs. Generally, the mean cecal concentrations of volatile fatty acids were higher upon resi stant starch feeding to rats given semi-synthetic diets, but the effects we re only significant for butyrate and total volatile acid concentration when retrograded high-amylose corn starch was supplied. On the contrary, rats r eceiving resistant starch added to the conventional diet showed no signific ant influences on cecal butyric acid and total volatile fatty acid concentr ations. Also in pigs, no significant effects of enzyme resistant starch int ake on colonic volatile fatty acid concentrations were found. No significan t effects of enzyme resistant starch intake on portal blood volatile fatty acid concentrations were observed in rats. In general, the amount of butyri c acid as part of the total volatile acids was substantially lower in the p ortal blood as compared with the cecum, suggesting that butyric acid was gr eatly metabolized by the intestinal wall. (C) 1999 Elsevier Science Inc.