The effect of roughage or concentrate feeding and rumen retention time on total degradation of protein in the rumen

Abstract

SUMMARY Samples of soya-bean meal, groundnut meal, sunflower meal and fish meal were incubated in nylon bags in the rumens of sheep receiving either whole barley or dried grass. For the vegetable sources of protein the rate of disappearance of protein was greater when they were incubated in the rumens of sheep receiving dried grass than in sheep receiving whole barley. The rate of disappearance of fish meal did not vary between sheep fed whole barley or dried grass. Rate of outflow of protein particles from the rumen was determined by rendering the protein supplement totally indigestible by a treatment with sodium dichromate. The rate of outflow was greatest with sheep receiving dried grass and increased with increasing feeding level. The mathematical expressions of degradation rate and outflow rate were combined to give the total amount of protein degraded in the rumen for the grass and barley diets at two levels of feeding. The amino acid composition of residues left in the nylon bags after 9 h of incubation were shown to be almost identical to the amino acid composition of the original protein supplement, indicating that the composition of the amino acid in the undegraded protein entering the abomasum essentially resembled that of the supplements.