Interactions of Phenolic Monomers With Digestion and Metabolism

Phenolic monomer content of alfalfa hay, soybean stover, smooth bromegrass hay and ensiled cornstalks was determined. High-pressure liquid chromatography was used to identify and quantitate p-coumaric, ferulic, gallic, p-hydroxybenzoic, protocatechuic, salicyclic, syringic and vanillic acids, and p-hydroxybenzaldehyde, syringaldehyde and vanillin in alkali extracts and products of nitrobenzene oxidation. Intact roughages and isolated cell walls were examined. Most alkali-labile phenolics were present in both the cell soluble and cell wall fractions, whereas nitrobenzene oxidation products were restricted to cell wall material. Roughages differed in content of phenolic monomers, with grasses generally having higher concentrations. In vitro incubation of alfalfa hay, smooth bromegrass hay and ensiled cornstalks with rumen fluid resulted in apparent digestion of phenolics associated with cell wall material. Roughages differed in digestibility of specific compounds. Inclusion of roughage phenolic monomers in a semipurified substrate for the fermentation with rumen microorganisms depressed substrate digestion. Salicyclic acid had the greatest negative effect on cellulose digestion, vanillin depressed starch digestion to the greatest extent, and only protocatechuic acid inhibited protein degradation. Rumen microbes extensively metabolized phenolic monomers to unidentified products. Intake, growth and feed efficiency of rats were reduced when phenolic monomers were included in the diet. p-Coumaric, ferulic and protocatechuic acids were similar in their effects, salicylic acid was significantly more detrimental, while vanillin tended to alleviate some detrimental effects. Digestibility of the major nutrients (protein, starch, cellulose) was unaffected by phenolics. Urine from rats was found to contain large amounts of phenolic monomers, suggesting that metabolic disruption by absorbed phenolics may account for reduced performance. Using lanthanum as an external marker, digesta samples were taken from sheep with cannulas in the rumen, duodenum and terminal ileum. Digestibility of phenolic monomers in the various sections of the gastrointestinal tract varied among immature and mature alfalfa and tall fescue hays. Levels of soluble phenolics decreased between rumen and duodenum, but increased again in the ileum. Urine from sheep contained large amounts of phenolics, including many unidentified metabolites.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Animal Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Jung, Hans-Joachim Gerhard

• Agriculture, Animal Culture and Nutrition

Identifier

(UMI)AAI8302900

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70003