Fermentation, rather than enzymatic digestion, is the main reason for small intestinal starch disappearance in milk-fed calves.

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The effects of refined pectin and mango pulp on macronutrient digestion and small intestinal enzyme activity were studied in grower pigs. Diets based on wheat starch with and without apple pectin or dried mango fruit pulp were fed to 30 grower pigs for 21 days. Pigs were euthanized two hours postprandially, and their gastrointestinal contents recovered. Starch and protein digestion as well as α-amylase activity were all increased in pigs fed pectin. In contrast, fat digestion, lipase and protease (trypsin) activities were all significantly reduced in these pigs. Pigs fed the mango fruit pulp diet had intermediate effects compared with pigs fed refined pectin and control diets. The data suggests that pectin has a significant effect on digestive enzyme activity and subsequent influence on macronutrient digestion. The fact that pectin caused either an increase (α-amylase) or decrease (lipase, protease) in enzyme activity in digesta, which either did (starch, lipid) or did not (protein) associate with residual nutrient differences illustrates the complexity of small intestinal responses to added fibre in diets.