The nutritive value of concentrate feedstuffs for ruminant animals: Part II: In situ ruminal degradability of crude protein

The objective of the study was to generate a database of in situ ruminal degradability of crude protein (CP) from different samples of a range of concentrate feedstuffs comprising protein, energy or protein+energy feeds commonly offered to ruminant animals in European countries. The in situ disappearance of CP was calculated using the in situ nylon bag technique where the test feedstuffs were subject to ruminal incubation in four Friesian steers offered grass silage and concentrate. Disappearance of CP from the test feeds from the rumen was measured at 0, 2, 4, 8, 14, 24 and 48 h. The exponential model of Ørskov and McDonald (1979) was used to measure degradation kinetics of CP. Test protein feeds were sunflower meal (SUN), rapeseed meal (RAP), soyabean meal (SBM) and cottonseed meal (CSM). Test energy feeds were palm kernel meal (PK), pollard (PO), barley (BA) and beet pulp (BP). Test protein+energy feeds were maize distillers grains (MDG), maize gluten feed (MGF), copra meal (CO) and malt combings (MC). The effective degradability of CP (EDP) in the protein feed SBM, where outflow rate (k)=0.02 was not influenced (P>0.05) by the sample of feed used. For the energy feeds, the EDP in PO for k=0.05 h−1, 0.06 h−1 and 0.08 h−1 and EDP in BA for k=0.08 h−1 were not significantly affected (P>0.05) by the sample of feed used. The data has shown that for the majority of feeds examined in this study, the different samples of any one feed are not equal in nutritive value and it is necessary to screen feeds for nutritive value before using them in ration formulation systems.