The digestion of fibre by pigs. 2. Volatile fatty acid concentrations in large intestine digesta.

The effect of including lupin (Lupinus sp.) hulls, maize cobs, wheat bran and lucerne (Medicago sativa) stems in a basal fibre-free diet on the concentrations and the relative proportions of volatile fatty acids (VFA) in the proximal colon of pigs, 17-18 h after feeding, was studied. Concentrations of total VFA in the proximal colon increased with increasing levels of neutral-detergent fibre (NDF) intake, and this increase was highly dependent on the source of NDF in the diet. Molar proportions of the VFA were significantly affected by the level of NDF intake only in the cases of acetic and butyric acids, whereas the source of dietary NDF had a marked influence on the molar proportions of all acids. The results indicate that the extent of fermentative breakdown of fibre in the pig intestine can be influenced substantially by the type and the level of fibre in the diet.