FERULOYL-COUMAROYL-CARBOHYDRATE AND PARA-COUMAROYL-CARBOHYDRATE ESTERS FROM GRASS AND CELLULOSE DEGRADATION BY RUMINAL MICROORGANISMS

Phenolic compounds are a PrimarY limitation to forage digestibility, but the specific mechanism that limits microbial activity requires elucidation. The objective of this research was to determine the influence of phenolic acid-carbohydrate esters isolated from 'Coastal' bermudagrass (Cynodon dactylon L. Pers.) on cellulolysis by rumen microorganisms. One or 5 nM concentrations of O-[5-O-(trans-feruloyl)-alpha-L-arabinofuranosyl]-(1 --> 3)]-O-beta-D-xylopyranosyl- (1 --> 4)-D-xylopyranose (FAXX), 1 mM O-[5-O-(trans-p-coumaroyl)-alpha-L-arabinofura-nosyl]-(1 --> 3)-O-beta-D-xylopyranosyl-(1 --> 4)-D-xylopyranoses(PAXX), equivalent concentrations of free phenolic adds and equivalent concentrations of L-arabinose plus D-xylose were added to anaerobic incubation vials containing MN 300 cellulose. Inhibition of cellulolysis by about 24% in the 5 mM study appeared to be due to the sugars and not the phenolic moiety. These studies suggest that these free phenolic-carbohydrate esters have minimal effect on fiber-digesting microorganisms in the rumen.