Submitted to: Conference on Gastrointestinal Function
Publication Type: Abstract Only
Publication Acceptance Date: March 20, 2011
Publication Date: April 20, 2011
Citation: Flythe, M.D., Kagan, I., Gellin, G.L., Goff, B.M., Aiken, G.E., Cheeke, P.R. 2011. Phytochemicals that modulate amino acid and peptide catabolism by caprine rumen microbes. Conference on Gastrointestinal Function. p. 470.786. Technical Abstract: Background: Microbe-derived ionophores and macrolide antibiotics are often added to ruminant diets, and growth promotion and feed efficiency are among the benefits. One mechanism is inhibition of microbes that catabolize amino acids or peptides and produce ammonia. Plants also produce antimicrobial compounds. These experiments were initiated to determine the effects of three categories of phytochemicals on amino acid and peptide fermentation by microbes from the rumina of goats. Methods: Rumen fluid was collected from forage-fed Kiko goats (n=8 wethers), and used to inoculate either peptide- or amino acid- rich media. Amendments included the following extracts: hops (Humulus lupulus), soap bark tree (Quillaja saponaria), or red clover (Trifolium pratense), rich in '-acids, saponins, or isoflavones, respectively. Biochanin-A, a dominant red clover isoflavone, was also tested. Ammonia concentrations were determined at zero and 48 hours. Experiments were performed in triplicate and analyzed with Student’s t-tests. Results: Ammonia production was inhibited by hops ' –acids (30 ppm), clover isoflavones (20 ppm), biochanin A (30 ppm) and saponins (0.5%). The combined effect of biochanin A with either saponins or '-acids was similar to that of biochanin A alone, but only when peptides were the fermentation substrate. When amino acids were fermented, the addition of saponins counteracted the inhibitory effect of biochanin A. Furthermore, low concentrations (200 ppb) of saponin/biochanin A mixture caused an increase in the final ammonia concentration (P=0.02). There was a similar trend with the '-acid/biochanin A mixture (P=0.08) Conclusion: These three categories of phytochemicals have the potential to control wasteful ammonia production in the goat rumen. However, there was an apparent hormesis at low doses of phytochemical mixtures and a differential effect on amino acid and peptide fermentation in one case. Plant metabolites are quite diverse even in conventional forages, and these results indicate that potential interactions among metabolites cannot be ignored.