Intestinal digestibility of rumen undegraded protein of various feeds as estimated by the mobile bag technique

Abstract

Two experiments were conducted with cannulated dry cows to estimate, using the mobile bag technique, the intestinal digestibility of rumen undegraded protein (DRUP) of various feeds. Forages as well as concentrates were evaluated in Experiment 1, while mainly concentrates were evaluated in Experiment 2. Higher DRUP values were found in concentrates (average, 88.2%) than in forages (average, 70.8%). Within the latter, the highest digestibilities were observed in fresh feeds (average, 83.2%). Low digestibilities were observed in silages (average, 63.3%), grass haylage (55.4%) and straw (61.5%). In concentrate feeds, high DRUP values were found in fish meal (94.5%) and extracted meals (average, 96.5%), with the exception of rapeseed meal (57.1% and 80.3% in samples A and C, respectively) and linseed meal (85.4%). Somewhat lower DRUP values were noticed in common cereals (average, 91.5%), peas (92.5%), horse beans (85.8%) and blood + cereal meal (89.7%). The lowest digestibilities were found in oats (70.0%, 88.8% and 72.0% in samples A, B and C, respectively), wheat bran (70.9%) and meat and bone meal (72.4%). In contrast to the DRUP values derived from the balance experiments with sheep, which are used by the French PDI protein evaluating system, higher DRUP values were found in these experiments in high-quality extracted meals than in common cereals.