Fermentation of wheat bran and gum arabic in rats fed on an elemental diet.

1. Gum arabic and wheat bran were added to an elemental diet (100 g/kg) in order to study their metabolism in the caeca of adult male albino Wistar rats. 2. Dry stool weight (g/d) over 12 weeks was 0.70 (SE 0.05) on the elemental control diet. Wheat bran increased mean dry stool weight to 1.09 (SE 0.08), an increase of 56%. There was no significant difference between faecal weights (0.65 (SE 0.08)) of the gum-arabic-supplemented group and the unsupplemented group. 3. Wet caecal-sac weight, dry caecal-contents weight, and faecal and caecal bacterial mass (measured by 2,6-diaminopimelic acid) all increased significantly with the gum-arabic-supplemented diet but not with the wheat-bran-supplemented diet. 4. Total short-chain fatty acids (mostly acetate) increased in the caecum and faeces with the gum-arabic-supplemented diet but not with the wheat-bran-supplemented diet. 5. Breath hydrogen and methane production decreased to negligible amounts over the 12 weeks of the experiment.