Small Intestine

The part of the bowel which connects the stomach to the large intestine, comprising three sections, the duodenum, the jejunum, and the ileum with a total length of 15 – 22 meters and a capacity of 50-70Liters it comprises around 30% of the total digestive tract. Food passes quite rapidly through the small intestine and may move from the stomach to the large bowel in as little as 45 minutes, though it may take several hours, depending on the type of food.

Digestion of most starch, protein and fat occurs here by means of enzymes such as amylase, protease, and lipase secreted into the gut by the pancreas and intestinal wall. Nutrient absorbtion of sugars, amino acids, glycerol, and fatty acids is largely completed in the small intestine. When starch from grains is excessive, or resists penetration by amylase enzymes, some may pass undigested into the large intestine where it will be digested by microbial fermentation, sometimes with hind gut acidosis as a result which in turn may lead to colic.

Processing of cereal grains by milling, crushing, flaking, pelleting, micronization and extrusion processes are designed to improve nutrient digestibility, especially that of starch, by enzymes in the small intestine and thus to avoid starch overspill into the hind gut.

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