Abstract
The use of enzymatic techniques to characterize rumen metabolism was investigated. Assays were developed to estimate the activities of 14 enzymes in cell-free extracts of microorganisms collected from rumen contents of cows fed two diets, selected to produce widely different proportions of fermentation end products. The results reflected the differences between the two diets in metabolic potential, fermentation patterns, and microbial populations. The differences between the diets in the relative activities of succinic dehydrogenase and fumaric reductase, for example, indicated a shift in the microbial population favoring organisms of the Viellonella alcalescens type on the concentrate diet. The data presented indicate that, if employed carefully, enzymatic criteria can be utilized effectively in studies of rumen metabolism.