Utilization of Methionine and Methionine Hydroxy Analog by Rumen Microorganisms in Vitro

When incubated with rumen fluid under suitable conditions, methionine hydroxy analog, calcium acts like methionine in preventing inhibition of cellulose digestion by ethionine and in forming methanethiol and dimethyl sulfide. When inocula were from an animal receiving only cellulose, corn starch, urea, and water, cellulose digestion in vitro was depressed but less in the presence of methionine than in its absence. In all of these reactions, methionine appeared to function more effectively than did the methionine hydroxy analog. When methionine-14C was incubated with rumen fluid, radioactivity was detected in methionine, methionine sulfoxide, carbon dioxide, mercaptan (presumably methanethiol), and protein.