Antinutritional activity of a water-soluble pentosan-rich fraction from rye grain

A series of experiments was designed to analyze the antinutritive compound(s) in rye that depress nutrient utilization; these were found to be mainly associated with the rye flour fraction. The bran fraction, however, more effectively depressed feed intake than the flour fraction. A starch-rich isolate, which contained most of the antinutritive activity from rye, as well as a protein-rich isolate devoid of activity, were prepared from the flour. Treating the starch-rich isolate of rye flour with .1 N NaOH stabilized the antinutritive factor. Centrifugation of the NaOH isolate produced four fractions. The supernatant fraction contained considerable quantities of water-soluble and highly viscous pentosans and was the only fraction that significantly depressed nutrient utilization. Increasing additions of the water soluble fraction to a control diet resulted in nearly proportionate decreases in the retention of dry matter and fat. An ethanol fractionation produced an ethanol-insoluble precipitate that contained a two-fold increased concentration of the water-soluble pentosans and demonstrated a two-fold increase in antinutritive activity. These results support the hypothesis that the rye antinutritional compounds are viscous pentosans.