PHYSICOCHEMICAL PROPERTIES AND THE DEGRADATION OF OAT BRAN POLYSACCHARIDES IN THE GUT OF PIGS

Physico-chemical properties and the digestibility of carbohydrates (st arch, beta-glucan and arabinoxylan (AX)) were studied in the gastroint estinal contents of pigs fed diets based on oat bran. One diet was mad e of commercially prepared oat bran and another of oat bran milled to pass a 1 mm screen. The pigs were slaughtered and samples were collect ed quantitatively from 10 sites of the gastrointestinal tract either 1 or 3 h after the morning feeding. The viscosity of the liquid phase ( obtained by centrifugation) of the stomach and small intestinal conten ts varied greatly between animals, and was not significantly different between segments of the upper gastrointestinal tract. The molecular w eight of beta-glucan was reduced up to 20-fold in the upper gastrointe stinal tract but was of a relatively low digestibility until the termi nal ileum. The solubility (the fraction of the total content in the li quid phase of digesta after centrifugation) of beta-glucan varied from 0.25 to 0.58 in the stomach and small intestine, whereas the solubili ty of AX was in the range of 0.04-0.16. Microscopic examination of dig esta showed that beta-glucan was retained in intact endospermic cell w all structures, which remained evident until the distal small intestin e but was completely disrupted in the caecum. In spite of a cumulative digestibility of non-starch polysaccharides and AX of similar to 0.90 in the large intestine, identifiable fragments of aleurone cell walls resistant to complete microbial degradation remained.