Chemical and fluorescence microscopic analysis of fiber degradation of oat, Hard Red Spring wheat, and corn bran in rats

The degradation of dietary fiber from hard red spring (HRS) wheat, corn, and oat brans (respectively 25.7, 18.4, or 22.7% in diets) was studied in rats after 28 weeks of feeding. In animals fed the oat bran diet, 76 +/- 9% of neutral detergent fiber (NDF) was fermented. Although dietary fiber levels and compositions were similar in HRS wheat and corn bran diets, HRS wheat NDF showed greater fermentative degradation (particularly xylan) than corn NDF (31 +/- 3 vs 7 +/- 4%) (P 0.001). Dietary fiber degradation observed by fluorescence microscopy was negligible in corn bran, partial in HRS wheat aleurone layer, and extensive in oat aleurone layer, confirming NDF analysis. It is concluded that bran fiber fermentability cannot be predicted from its composition alone