Abstract

Abstract The effect of rumen incubation on the true indigestibility of feed protein in the digestive tract (TIFP) was studied for 10 concentrates. Only fish meal and soybean meal showed a constant TIFP independent of rumen incubation time or extent of rumen protein degradation. For the other feedstuffs, TIFP decreased to various degrees at increased ruminal protein degradation. For extracted rapeseed meal, maize gluten meal and guar meal, however, TIFP measured without pre-incubation in the rumen was also satisfactory as a basis for predicting the true digestibility of rumen undegraded feed protein in the intestine (TDRUP) for practical purposes. In contrast, TIFP for predicting TDRUP for peas, rapeseeds, lupin seeds, barley and oats should be determined on feed samples after rumen incubation.