Fermentation of oat fiber in the rat intestinal tract: a study of different cellular areas

Intestinal fermentation of dietary fiber from oat husk, bran, and white flour and a commercial oat bran was investigated through balance experiments in rats. Both solubility and monomeric composition of the fiber differed widely. Fiber from husk was only 0.5% soluble and nearly completely resistant to fermentation whereas fiber from bran (38% soluble) and white flour (24% soluble) was more fermentable (62% and 55% of the intake, respectively). Fiber from commercial bran (37% soluble) was most extensively fermented; only 19% of the fiber could be detected in feces. The fecal dry weight with the husk in the diet was significantly (p less than 0.001) higher than that for the other preparations. Most of the fecal dry weight increment for husk (approximately 95%) could be accounted for as fiber whereas only 45-65% of the increment was undergraded fiber for the other preparations. An additional 20-30% could be explained by protein and approximately 15% by fat with these preparations.