Isolation, partial characterization, and antinutritional activity of a factor (pentosans) in rye grain.

The role of isolated pentosans as the possible antinutritional factor in rye grain was investigated by using the chick as the bioassay animal. Pentosans were fractionated into water-soluble and insoluble fractions, and the content of the two major pentoses, xylose and arabinose, were quantitated. Puma rye contained 2.1 soluble and 7.7 % insoluble pentosans. When isolated pentosans supplied wheat-based diets with the same level of pentosans as that found in similarly formulated rye diets, the depression of growth was 20 and 55% for the soluble and insoluble pentosans, respectively. Both fractions depressed nutrient digestibility. At equal dietary levels, the soluble fraction was slightly more potent compared to the insoluble pentosans. The antinutritional activity of pentosans may be attributed to their ability to form highly viscous solutions which reduced the rate of digestion and/or absorption of nutrients and to the inability of the avian digestive system to digest pentosans.