IMPROVEMENT OF THE STREPTOMYCES-GRISEUS METHOD FOR DEGRADABLE PROTEININ RUMINANT FEEDS

The methods of Krishnamoorthy et al. [Krishnamoorthy, U., Sniffen, C.J ., Stern, M.D., Van Soest, P.J,, 1983. Evaluation of a mathematical mo del of rumen digestion and an in vitro simulation of rumen proteolysis to estimate the rumen undegraded nitrogen content of feedstuffs. Br. J. Nutr. 50, 555-568] and Poe et al. [Roe, M.B., Sniffen, C.J., Chase, L.E., 1990. Proc. Cornell Nutrition Conference, Dept. of Animal Scien ce, Cornell University, Ithaca, NY, pp. 81-88], and a new one presente d in this paper have been compared, and a revised procedure is propose d using a fixed ratio of enzyme to true protein (TP) determined by tun gstic acid precipitation. A comparison of the three methods shows that they are statistically different. The ratio of enzyme has also signif icant effect (p > 0.01) on the estimate of degradable nitrogen when co mpared to the fixed concentration of enzyme in the original method. Th e effect of buffer pH (6.7 vs. 8) on degradation of protein sources wa s also statistically significant (p > 0.05) with somewhat higher degra dation at pH 8. (C) 1998 Elsevier Science B.V.