POSTPRANDIAL VARIATIONS IN THE ACTIVITY OF POLYSACCHARIDE-DEGRADING ENZYMES OF FLUID-ASSOCIATED AND PARTICLE-ASSOCIATED RUMINAL MICROBIAL-POPULATIONS

The distribution and specific activities of polysaccharide-degrading e nzymes were monitored during the postprandial period in the liquid-ass ociated bacteria (LAB), liquid-associated protozoa (LAP), and solid-as sociated microbes (SBFP) isolated from ruminal contents of cattle fed a high-cereal diet. Polysaccharide depolymerase activities were highes t in the SBFP and the LAP populations. The postprandial variations in the specific activity of amylase were similar within the subpopulation s. However, carboxymethylcellulase and xylanase activities increased i n the first 5 h after feeding in the LAP, but were highest at the end of the postprandial period in the SBFP. Glycosidases involved in the f ermentation of soluble carbohydrates increased significantly immediate ly after feeding in the liquid-associated microbes. Beta-D-Glucosidase and beta-D-xylosidase were most active in the SBFP and were maximal 2 3 h after feeding. The activities of the plant cell wall polysaccharid e-degrading enzymes and glycosidases in the SBFP were inversely relate d to ruminal pH; however, the activity of enzymes in the liquid-associ ated populations were highest in the immediate post-feed period when r uminal pH was lowest.