Dietary influences on carbohydrases and small intestinal starch hydrolysis capacity in ruminants

Data describing the influence of diet composition and intake on amylolytic and disaccharidase activities in the ruminant small intestine are reviewed. Changing dietary components from forage to grain increased pancreatic alpha-amylase activities in most studies; however, when metabolizable energy intake was equalized, concentrations of alpha-amylase in the pancreas and the total quantities in the small intestinal lumen were greater in forage-fed than in grain-fed animals. Concentration of pancreatic alpha-amylase increased with dietary energy intake. Changing diet composition or metabolizable energy intake exerted a small effect on intestinal disaccharidase activities, with hydrolytic capacity altered principally through changes in intestinal length. Other studies suggest a small contribution of intestinal disappearance of carbohydrates to net portal appearance of glucose. The fate of large portions of intestinal carbohydrate disappearance have not been adequately defined. For the importance of intestinal carbohydrate supply to be understood, the quantity of carbohydrate undergoing both enzymatic hydrolysis and absorption must be determined.