Maintenance of protozoa and methanogens, and fiber digestion in rumen-simulating continuous culture

Abstract

An apparatus for rumen-simulating continuous culture (fermenter of 1.21 capacity) was constructed which was equipped with a dialyzing system, a sieving system, a pH controller, and a device for collecting methane. When dried grass and concentrate (each 10 g/l culture/d) were given twice daily with a small amount of clover juice and the fluid dilution rate was set at 1.5/d, oligotrich protozoa and Dasytricha were maintained at ca. 2 x 105/ml and 2 x 104/ml, respectively, at least for 10 d. On the other hand, Isotricha failed to grow and disappeared within 10 d. Care to keep anaerobiosis was needed for the maintenance of methanogens at a reasonable level. Irrespective of whether or not pH was controlled, there was no significant difference in the levels of protozoa and methane production under these conditions. However, when the concentrate was doubled (dried grass : concentrate =1: 2) without pH control, the drop in pH after feeding was large and protozoa were markedly decreased except for entodinia which are relatively resistant to low pH. Methane production and digestion of neutral detergent fiber (NDF) were also reduced with high concentrate. When pH was kept at 6.7 under these conditions, all groups of protozoa increased (total number, ca. 3 x 105/ml) except for Isotricha, and methane production and NDF digestion were also increased. These results suggest that the addition of an appropriate level of concentrate enhances fiber digestion, unless pH is dropped too much. © 1993, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.