Interactions Among Phenolic Monomers and In Vitro Fermentation

Abstract

Phenolic monomers commonly in four roughages (alfalfa hay, soybean stover, smooth bromegrass hay, or ensiled cornstalks) were included in semipurified substrates in in vitro fermentation experiments. In Experiment 1, phenolics were added as mixtures of compounds to mimic phenolic monomer composition of roughages. In Experiment 2, phenolics were added individually at 1.0, 5.0, and 9.0%. Cellulose, starch, and protein digestions were measured in these experiments. In Experiment 3, eleven phenolic monomers were added to the substrate individually at 1.0%, and residues were analyzed after 48 h of digestion for remaining phenolic monomers. Mixtures of phenolic monomers tested in Experiment 1 did not affect cellulose, starch, or protein digestion. The higher percentages of phenolic monomers tested in Experiment 2 resulted in linear decreases of cellulose and starch digestion with increasing phenolic concentrations. Salicyclic acid produced the greatest inhibition for cellulose degradation, whereas vanillin was most effective for depressing starch digestion. Protein digestion was inhibited only by protocatechuic acid additions to the substrate. Recoveries of phenolic monomers in Experiment 3 were low for all compounds. The presence of several unidentified compounds in the fermentation residues suggested extensive microbial metabolism of phenolic monomers. © 1983, American Dairy Science Association. All rights reserved.