Intestinal Digestibility of Rumen Undegraded Dietary Protein from Tropical Roughages Estimated by the Mobile Bag Technique

Abstract

Instestinal digestibility of dietary protein in thirteen tropical roughages was estimated using the mobile bag technique on both intact feeds and on samples which had been pre-incubated in the rumen for 8, 24 or 96 h. For all the tested feedstuffs the total digestibility of protein was increased substantially by rumen pre-incubation. The digestibility of rumen undegraded protein after 24 h rumen incubation varied from 0 to 46% for grasses, from 2 to 42% for legumes, and was zero for leucaena. The results showed a generally low intestinal digestibility of rumen undegraded protein, and indicate that long retention time in the rumen is necessary to obtain maximum utilization of the protein in these feeds. The hypothesis that feeds contain a fraction which is both undegradable in the rumen and indigestible in the intestine, and that this fraction can be estimated by the mobile nylon bag technique from the intact protein, was not valid for the tropical forages tested.

Key Words:

• ruminants
• grass
• legumes
• leucaena
• nylon bag