Comparison of in situ and Cornell methods of estimating rumen degradable protein of ruminant feedstuffs

Abstract

The objective of this experiment was to compare in situ and Cornell methods of estimating the rumen degradable protein (RDP) of a variety of ruminant feedstuffs. Samples of barley meal, soyabean meal, fishmeal, linseed meal, maltculms, maize gluten meal, double zero rapeseed meal, high glucosinolate rapeseed meal, sunflower meal and field beans were used for the Cornell in vitro technique. The same concentrate samples were analyzed by Mirza (1993) for in situ protein degradation. Regression analysis was used to relate the Cornell RDP values to corresponding in situ values. The Cornell RDP estimates averaged 0.10 less than the in situ values. However, the Cornell RDP estimates were significantly correlated with those of the in situ method for the same feeds (r2 0.76; P<0.001). Comparison of other in situ and Cornell data on nominally similar feedstuffs showed some level of agreement in the RDP estimates especially of concentrate and by-product feedstuffs. The Cornell model therefore compares favourably with the in situ method for estimating RDP of concentrate and by-product feedstuffs. There were however differences in the magnitude of the RDP values with the in situ method generally recording higher values.