| Abstrakt: |
The composition of the carbohydrate substrate in the in vitrorumen fermentation was found to influence the concentration of valeric acid present in the medium at the end of 30-hr, experiments. Little or no valeric acid was synthesized when cellulose was the carbohydrate substrate or, alternatively, the ultilization exceeded the rate of formation under these conditions. Likewise, if valeric acid was added at the start of an experiment, the final level was only 40 to 60% of the amount added initially. However, 2–10 mg. of valeric acid per 100 ml. of the in vitromedium was found in flasks containing a carbohydrate mixture composed of 1/3 to 1/2 starch with cellulose making up the remainder. Furthermore, valeric acid added to the starch-cellulose medium at the start of the experiment did not appear to be utilized by the micro-flora.Rumen organisms grown in a medium deficient in urea nitrogen appeared to synthesize valeric acid; however, as the level of added nitrogen was increased the level of valeric acid in the flasks decreased. This change in valeric acid concentration was accompanied by an increase in the amount of cellulose digested and in the content of trichloroacetic acid-insoluble nitrogen in the flasks, suggesting that as microbial growth increased the rate of valeric acid synthesis decreased and/or the rate of utilization increased. |
