ARS | Publication request: Antimicrobial Effects of Red Clover (Trifolium pratense) Phenolic Extract on the Ruminal Hyper Ammonia-producing Bacterium, Clostridium sticklandii SR

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 8, 2010
Publication Date: January 20, 2010
Citation: Flythe, M.D., Kagan, I. 2010. Antimicrobial Effects of Red Clover (Trifolium pratense) Phenolic Extract on the Ruminal Hyper Ammonia-producing Bacterium, Clostridium sticklandii SR. Curr Microbiol (2010) 61:125-131.

Interpretive Summary: Many rumen bacteria are proteolytic, but ammonia production is largely attributable to a phylogenetically diverse group of bacteria called the hyper ammonia-producing bacteria (HAB). When protein is broken down in the rumen, microbes take up the peptides and amino acids, and the major product is ammonia. Rumen bacteria assimilate some of the ammonia, but much of it passes into the blood stream and is subsequently lost in the urine. Ruminant producers have to feed supplemental protein to make up for this loss. Recent research has shown that plant secondary metabolites can have beneficial effects on rumen fermentation. In particular, red clover is known for low rates of proteolysis, but effects on HAB have not been determined. This work was initiated to: 1) analyze the soluble phenolic constituents from a red clover cultivar, and 2) determine if any of these compounds have antimicrobial activity against the bovine HAB, Clostridium sticklandii SR. Our results revealed the clover isoflavone, biochanin-A, could inhibit this bacterium.

Technical Abstract: Ruminal proteolysis and subsequent amino acid degradation represent considerable economic loss in ruminant production. The hyper ammonia-producing bacteria (HAB) are responsible for amino acid deamination in the rumen. HAB can be controlled with ionophores, but they are also susceptible to plant-synthesized antimicrobials. Red clover (Trifolium pratense) is rich in soluble phenolics, and it is also more resistant to proteolysis than other legumes. The goal of this study was to identify phenolic compounds from Trifolium pratense cultivar Kenland, and determine if any of the compounds possessed antimicrobial activity against the bovine HAB, Clostridium sticklandii SR. HPLC analysis revealed that clover tissues were rich in the isoflavonoids formononetin and biochanin-A, particularly in plants left to wilt for 24 h. Biochanin-A inhibited C. sticklandii in bioassays that employed thin-layer chromatography (TLC). Both clover extracts and biochanin-A inhibited the growth of C. sticklandii in broth culture, but formononetin had no effect. These results indicate that clover phenolic compounds may have a role in preventing amino acid fermentation as well as proteolysis.