Starch and fiber fractions in selected food and feed ingredients affect their small intestinal digestibility and fermentability and their large bowelfermentability in vitro in a canine model

The digestion of legumes, cereal grains, cereal and potato flours and grain -based foods in dogs was studied using two in vitro model systems. The firs t simulated the stomach and small intestine through the additions of acid a nd enzymes and large bowel fermentation through use of fecal inocula from d ogs, and the second simulated small intestinal fermentation using canine il eal chyme as the bacterial source. All substrates were analyzed for total d ietary fiber (TDF) including insoluble and soluble components, and starch f ractions: rapidly digestible starch, slowly digestible starch, resistant st arch (RS) and total starch. Legumes had high TDF and RS concentrations (mea n 36.5 and 24.7%, respectively), resulting in lower ileal digestible starch and total digestible starch concentrations (mean 21 and 31%, respectively) . Seventy-four percent of the TS in the cereal grains group was rapidly dig estible starch plus slowly digestible starch compared with the flour group, where the corresponding value was 95%. This related to the processing of c ereals to flours, in which TDF and RS concentrations were reduced markedly. This increased ileal digestible starch concentrations in the flour group ( 65%) versus the cereal grains group (60%), Ileal digestion of starch in gra in-based food products like macaroni and spaghetti was high (96 and 92%, ex pressed as a percentage of TS, respectively). Fermentation of substrates wi th ileal microflora was influenced by substrate chemical composition, with the flour group exhibiting the highest organic matter disappearance values. The legume group had a high total short-chain fatty acid concentration (7. 8 mmol/g organic matter fermented), perhaps as a result of fermentation of TDF as well as starch components. A database such as this one provides info rmation about utilization of foods and feeds in the dog and potentially in humans.