OAT BRAN BUT NOT A BETA-GLUCAN-ENRICHED OAT FRACTION ENHANCES BUTYRATE PRODUCTION IN THE LARGE-INTESTINE OF PIGS

Digestibility of polysaccharides and other macronutrients and the meta bolic response of the microflora in the large intestine to a low dieta ry fiber wheat flour diet and three enriched diets with equal amounts of added dietary fiber (oat bran, a beta-glucan-enriched oat fraction and insoluble oat residues) were studied in ileal-cannulated pigs. The digestibility of starch was high in the small intestine (98-100%). At this site of the gastrointestinal tract there was also a significant degradation of mixed linked beta(1 --> 3;1 --> 4)-D-glucan (beta-gluca n) (45-54%), whereas arabinoxylan was quantitatively recovered in ilea l effluent. Type and amount of polysaccharides passing the ileal-cecal junction had little effect on the density of microorganism in the lar ge intestine (approximately 10(10) viable counts/g digesta) but did ha ve a high impact on the activity of the flora in colon as measured by the concentration of ATP in digesta. The relative proportion of butyra te in the short-chain fatty acids in the luminal contents of the large intestine was 6.6-8.4% when the low dietary fiber wheat flour diet wa s fed. However, when either oat bran or insoluble residues were includ ed in the diet, the level was raised to 9.3-11.2%. No effect was seen after the addition of the beta-glucan-enriched fraction. This study sh owed that arabinoxylan and not beta-glucan in the cell walls of oat br an was responsible for the enhanced butyrate production of oat bran.