Hydrogen production and transfer in the rumen

Hydrogen is a central metabolite in rumen fermentation and its partial pressure is an important determinant of rumen methanogenesis. The balance of hydrogen ion (H+) and dissolved hydrogen gas (H2) concentrations directly determine the redox potential of the rumen and therefore the possible extent of oxidation of feedstuffs. Differential permeability of the bacterial membrane to H+ and H2 means the proportions of these metabolites in the extracellular fluid will differ from their proportions within the bacterium. Interpretation of extracellular H2 concentration in the bulk fluid is also complicated by inter–species hydrogen transfer among H2 producing and utilising rumen organisms which live in close physical (syntrophic) associations. The role of H2 concentration in determining the array of fermentation products and the efficiency of energy capture by rumen organisms is discussed. Developing a greater understanding of rumen hydrogen metabolism may present new opportunities for the control of rumen methanogenesis. Hydrogen production and transfer in the rumen