Effect of Nickelous and Other Metal Ions on the Inhibition of Rumen Bacterial Metabolism by 3-(3′-Isocyanocyclopent-2-Enylidene)Propionic Acid and Related Isocyanides

3-(3′-Isocyanocyclopent-2-enylidene)propionic acid at a concentration of 2 to 5 μg ml−1 inhibited cellulose digestion by a mixed culture of rumen microorganisms and in other experiments inhibited the degradation of timothy hay (Phleum pratense ) in a digestibility test. At isocyanide concentrations of 12 μg ml−1 the fermentation activity of rumen fluid, measured by its dehydrogenase activity, was inhibited but not abolished. All of these isocyanide effects were reversed by the incorporation of nickelous ion into the solutions of the systems under study. The activity of 1 mol of isocyanide is reversed by about 1 mol of Ni2+ and, in the case of the cellulose digestion test, by about 1 mol of Co2+ . Of some 15 other ions tested only Pd2+ and possibly chromium reversed the effect of the isocyanide.