Studies of rumen function in an in vitro continuous culture system

An in vitro continuous culture system to simulate processes in the rumen is described. This comprises a culture vessel (Fig. 2) fed continuously with pelleted solid feed (Fig. 1); artificial saliva also enters the vessel while effluent leaves it continuously in two streams, one is filtered and the other simply overflows (Fig. 1). In this way liquid and solid turnover times may be manipulated independently; in a trial experiment the former and latter were 6.3% and 3.4% per hour respectively. In four replicated experiments a steady-state was achieved in 5-6 days with a feed of barley, tapioca, fishmeal, urea and straw and maintained for a further 7 to 14 days. During a steady-state period, rumen characteristics in terms of protozoal count, pH, redox potential, total volatile fatty acid concentration and ammonia concentration were stable and similar to those found in the rumens of animals given similar diets. Flows of microbial N compounds were assessed by infused Na2H32PO4 with the artificial saliva and estimating the 32P label incorporated in bacterial fractions. The system demonstrably provided a satisfactory means for studying many aspects of rumen function.