In Vitro Simulation of Rumen Fermentation: Apparatus and Effects of Dilution Rate and Continuous Dialysis on Fermentation and Protozoal Population

Abstract

Studies were conducted with an in vitro simulation of the rumen fermentation using a specially designed artificial rumen of permeable continuous culture type which would simulate both the removal of end-products of fermentation and flow of ingesta. Experiments were made to determine the effects of dialysis and dilution rate on the fermentation and microbial population in the continuous culture, using permeable and impermeable culture systems for 4 days with low dilution rate (0.5 volume turnovers/day) and high dilution rate (1.2 or l.5 volume turnovers/day). In the impermeable culture systems with low dilution rate, the accumulation of the end-products of fermentation inhibited microbial growth. Metabolic stability of the in vitro system occurred when high dilution rates were adopted, but a decrease in the numbers of protozoa was observed. In the permeable culture system with low dilution rate (0.5 volume turnovers/day), the fermentation patterns showed resemblance to those obtained in vivo, and the population of entodiniomorphs was maintained. The numbers of holotrich protozoa could not be maintained, and the variations in the composition of volatile fatty acids (VFA) and the content of deoxyribonucleic acid (DNA) indicated that there were some shifts in microbial population in every experiment.