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 < 0.001) higher than that for the other preparations. Most of the fecal dry weight increment for husk (~95%) could be accounted for as fiber whereas only 45-65% of the increment was undegraded fiber for the other preparations. An additional 20-30% could be explained by protein and ~15% by fat with these preparations.