Impact of physico-chemical properties of dietary starch on digestive physiology in pigs

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Dietary starch is a fascinating nutrient for monogastric species. Starches ranging from low to high amylose range from rapidly digestible in the upper gut to fermentable in the lower gut due to changes in physico-chemical characteristics. Starch can thus be a source of glucose or short-chain fatty acids (SCFA). In swine nutrition, the paradigm is that fermentable starch is a negative dietary factor due to its fermentation and suppressive effects on whole body nutrient utilization. In contrast, in human nutrition, fermentable or resistant starch is gaining popularity due to its suppression of the rate of nutrient absorption and stimulation of intestinal health. The underlying mechanisms that exist throughout the intestine to change metabolism from rapidly digestible starch to fermentable starch are poorly understood, but include changes in nutrient transporters, chemo-sensors, gut structure and permeability, and incretin signalling to the pancreas. To clarify these mechanistic changes, pig models including 1) distal ileum cannulation to collect digesta, 2) portal-vein catheterization to sequentially sample blood, 3) slaughter method to collect intestine tissue and digesta, and 4) indirect calorimetry will be used. This combination allows measuring of total extent, rate, and site of starch digestion and whole body energy and nutrient use. Finally, the effects of starch flow on maintenance of intestinal structure and of non-digested starch on microbial populations can be studied. The combination of four distinct pig research models and the availability of purified dietary starches ranging in their physico-chemical properties is unique and is a robust tool to study the kinetics of flow of starch and its metabolites, and their impact on digestive physiology. The proposed work strengthens our efforts to link dietary carbohydrates to a wide array of nutritional and physiological variables, and to assess negative and positive effects of carbohydrates on whole body nutrient utilization. The proposed work is important to better predict and manage nutrient flow in pigs. Finally, the work stimulates efforts to fractionate and characterize starch contained in Canadian cereals and pulses, creating opportunities for Canadian agri-food industries.