Maintenance of the rumen microbial population in continuous culture

The design and use of an apparatus for continuous in vitro cultivation of the mixed bovine rumen microbial population are described. Data relative to the concentrations and proportions of volatile fatty acids produced, methanogenesis, carbon dioxide production, and survival of bacteria and protozoa indicated that an essentially normal in vivo fermentation pattern was maintained in vitro for experimental periods of from 3 to 10 days. The continuous cultures were responsive to major changes in type of feed intake. A change from grain to hay resulted in increased acetate and decreased propionate production, whereas decreased acetate and increased propionate resulted when feed intake was changed from hay to grain. Methanogenesis, volatile fatty acid production, and the numbers of microorganisms in the cultures were proportional to the amount of feed materials added up to levels calculated to approximate the in vivo maintenance requirement of the adult bovine.