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

对于单胃动物来说，膳食淀粉是一种令人着迷的营养物质。直链淀粉含量从低到高不等，由于理化特性的变化，直链淀粉从上肠的可快速消化到下肠的可发酵。因此淀粉可以是葡萄糖或短链脂肪酸（SCFA）的来源。在猪营养学中，通常认为可发酵淀粉是一种不利的饲粮因子，因为它会发酵并抑制全身营养物质的利用。相比之下，在人类营养中，可发酵或抗性淀粉由于其抑制营养吸收速度和刺激肠道健康而越来越受欢迎。肠道中存在的将代谢从快速消化淀粉转变为可发酵淀粉的潜在机制尚不清楚，但包括营养转运蛋白、化学传感器、肠道结构和通透性以及肠促胰岛素向胰腺信号的变化。为了阐明这些机制变化，猪模型包括：1)回肠远端插管收集食糜，2)门静脉插管顺序采血，3)屠宰法收集肠组织和食糜，4)间接量热法。这种组合可以测量淀粉消化的总程度、速率和位置以及整个身体的能量和营养利用。最后，可以研究淀粉流量对肠道结构维持的影响以及非消化淀粉对微生物种群的影响。将四种不同的猪研究模型和不同理化性质的纯化饲粮淀粉结合起来，是研究淀粉及其代谢物流动动力学及其对消化生理影响的有力工具。本研究加强了我们将膳食碳水化合物与一系列营养和生理变量联系起来的努力，并评估了碳水化合物对全身营养利用的消极和积极影响。这项工作对更好地预测和管理猪的营养流动具有重要意义。最后，这项工作促进了对加拿大谷物和豆类中含有的淀粉进行分馏和表征的努力，为加拿大农业食品工业创造了机会。

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.