|HARRISON, BRANDON - University Of Kentucky|
|GOFF, BEN - University Of Kentucky|
Submitted to: Agriculture, Food and Analytical Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2013
Publication Date: 9/1/2013
Citation: Flythe, M.D., Harrison, B., Kagan, I., Klotz, J.L., Gellin, G.L., Goff, B.M., Aiken, G.E. 2013. Antimicrobial activity of red clover (Trifolium pratense L.) extract on caprine hyper ammonia-producing bacteria. Agriculture, Food and Analytical Bacteriology. 3:176-185.
Interpretive Summary: As ruminants, goats can utilize a wide range of fibrous plant materials because of the symbiotic rumen microbes. However, some microbes conduct wasteful processes. Ruminal hyper ammonia-producing bacteria (HAB) convert feed amino acids into ammonia before the animal can absorb them. Consequently, less protein is available for animal growth, leading to greater expenses in raising livestock. HAB can be controlled by antimicrobial compounds. This study examined the abilities of red clover extract and one of its components, biochanin A, to control HAB in the goat rumen. Ammonia production was measured in goat rumen fluid treated with different concentrations of (1) pure biochanin A or (2) enough red clover extract to provide those same concentrations of biochanin A. At a biochanin A concentration of 30 ppm, ammonia production in goat rumen fluid decreased significantly. A pure culture of a caprine HAB was inhibited by biochanin A, but only if peptides from other rumen bacteria were present. These results show a synergistic relationship between a antimicrobial plant compound and an antimicrobial peptide that is naturally produced by rumen bacteria.
Technical Abstract: One of the inefficiencies in rumen fermentation is the catabolism of feed amino acids and peptides by hyper-ammonia-producing bacteria (HAB). The HAB can be controlled through selective inhibition with antimicrobials. In vitro ammonia production by uncultivated goat rumen bacteria was inhibited by red clover (Trifolium pratense L.) phenolic extract. One component of the extract was the isoflavone, biochanin A. When the biochanin A concentration was 30 ppm, amino acid fermentation and ammonia production decreased. The effect of biochanin A was tested on a cultured caprine HAB isolate (Peptostreptococcus spp.). The growth of the HAB was not inhibited by biochanin A alone, even if the concentration was as much as 200 ppm. However, the addition of sterile rumen fluid (5%) caused growth inhibition at 2 ppm biochanin A. To determine what component in the rumen fluid acted synergistically with biochanin A, the growth experiment was repeated with either a mixture of volatile fatty acids (VFA) or the supernatant of the bacteriocin-producing Streptococcus bovis HC5 (5% v/v) in place of the rumen fluid. The combination of biochanin A and S. bovis supernatant caused growth inhibition, but VFA had no effect. These results are consistent with the hypothesis that biochanin A potentiates the activity of other heat-stable antibacterial compounds that are present in the rumen environment, and that the spectrum of activity could depend on the inhibitors present. Red clover extract and its components represent plant-based feed additives that could be used to control ammonia production in goats and other ruminants.