Oat Bran but Not a β-Glucan-Enriched Oat Fraction Enhances Butyrate Production in the Large Intestine of Pigs

Abstract

Digestibility of polysaccharides and other macronutrients and the metabolic response of the microflora in the large intestine to a low dietary 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-glucan) (45-54%), whereas arabinoxylan was quantitatively recovered in ileal effluent. Type and amount of polysaccharides passing the ileal-cecal junction had little effect of the density of microorganism in the large intestine (approximately 10(10) viable counts/g digesta) but did have a high impact on the activity of the flora in colon as measured by the concentration of ATP in digesta. The relative proportion of butyrate 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 was fed. However, when either oat bran or insoluble residues were included 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 showed that arabinoxylan and not beta-glucan in the cell walls of oat bran was responsible for the enhanced butyrate production of oat bran.