Biochanin A improves fiber fermentation by cellulolytic bacteria

Authors: HARLOW, BRITTANY - ORISE FELLOW; AIKEN, GLEN; Flythe, Michael

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2017
Publication Date: 11/7/2017
Citation: Harlow, B.E., Aiken, G.E., Flythe, M.D. 2017. Biochanin A improves fiber fermentation by cellulolytic bacteria. Journal of Applied Microbiology. 124(1):58-66.

Interpretive Summary: Cattle evolved as strict herbivores consuming diets rich in structural carbohydrates (e.g., cellulose and hemicellulose). Cattle do not produce the enzymes necessary for cellulose breakdown; therefore, cellulolytic microorganisms native to the rumen play an essential role in the nutrition of cattle consuming high fiber diets. It is also widely accepted that fiber fermentation in the rumen is not optimal. For this reason, strategies for increasing the efficiency of fiber degradation in the rumen are of great interest to improve cattle growth performance. A laboratory experiment with rumen fluid using ground hay as a fiber source, found that the addition of biochanin A, an isoflavone produced by the pasture legume red clover, increased fiber digestibility. Biochanin A did not increase the number of viable cellulolytic bacteria in rumen fluid, but did influence competition between cellulolytic bacteria species. The results of this study suggest that biochanin A could be utilized to improve fiber digestibility and animal performance in cattle consuming a high fiber diet. Future research is needed to evaluate the effect of biochanin A on fiber digestibility and cattle growth performance in vivo.

Technical Abstract: The objective was to determine the effect of the isoflavone biochanin A (BCA) on rumen cellulolytic bacteria and consequent fermentative activity. When bovine microbial rumen cell suspensions (n = 3) were incubated (24 h, 39 °C) with ground hay, cellulolytic bacteria proliferated, short chain fatty acids were produced and pH declined. Biochanin A (30 µg mL-1) had no effect on the number of cellulolyic bacteria or pH, but increased acetate, propionate and total SCFA production. Addition of BCA improved total digestibility when cell suspensions (n = 3) were incubated (48 h, 39 °C) with ground hay, Avicel, or filter paper. Fibrobacter succinogenes S85, Ruminococcus flavefaciens 8, and R. albus 8 were directly inhibited by BCA. Synergistic antimicrobial activity was observed with BCA and heat killed cultures of cellulolytic bacteria, but the effects were species dependent. These results indicate that BCA improves fiber degradation by influencing cellulolytic bacteria competition and guild composition. BCA could serve as a feed additive to improve cellulosis when cattle are consuming high fiber diets. Future research is needed to evaluate the effect of BCA on fiber degradation and utilization in vivo.