Comparative studies of ruminal protein degradation using in situ and enzymatic in vitro methods

Abstract

The ruminal protein degradation can be estimated in situ and by in vitro methods. The Streptomyces griseus protease (SGP) is used in SGP-method (SGPM) to estimate rumen undegraded protein in feedstuffs in vitro. However, feed-specific protein-carbohydrate complexes require additional carbohydrase in SGPM to reduce differences to in situ crude protein degradation data. It was shown that SGP and a carbohydrase can be incubated simultaneously under the SGPM conditions without significantly reducing the carbohydrase activity. The simultaneous incubation of a α-amylase or a cellulolytic enzyme mixture with SGP did not reduce the differences between in situ and in vitro ruminal crude protein degradation. The incubation conditions and enzymatic interactions might lead to insufficient degradation of protein-carbohydrate complexes. Pre-incubation of carbohydrases prior to the SGPM may be more promising as recommended specific incubation conditions of the carbohydrase can be considered.