|HARLOW, BRITTANY - Oak Ridge Institute For Science And Education (ORISE)
Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2017
Publication Date: 3/12/2017
Citation: Harlow, B.E., Flythe, M.D., Aiken, G.E. 2017. Effect of biochanin A on corn grain (Zea Mays) fermentation by bovine rumen amylolytic bacteria. Journal of Applied Microbiology. 122(4): 870-880.
Interpretive Summary: Ruminal acidosis is a common digestive disorder in cattle that has both significant economic and animal welfare implications. Acute acidosis is characterized by a ruminal pH below 5.0 and typically occurs when an animal is abruptly switched from a forage diet to a high-starch diet. A rapid increase of starch in the rumen can lead to an increase in bacteria that produce lactic acid and causes the decline in rumen pH. Antimicrobial feed additives can be employed in the treatment or prevention of acute rumen acidosis in cattle, but a concern of the spread of antibiotic resistance has caused steps to be taken nationally and internationally to minimize or eliminate the use of antibiotics in food animal production systems. A laboratory experiment with rumen fluid using ground hay as a fiber source and corn as a high-starch substrate found that addition of biochanin A, an isoflavone produced by red clover, decreased the rate and total disappearance of starch. Furthermore, addition of biochanin A also increased the cellulolytic bacteria responsible for degrading fiber (cellulose), which increased overall dry matter digestibility. Biochanin A has potential use for reducing the incidence of rumen acidosis when high-starch diets are fed, or to improve fiber digestion with red clover is overseeded into grass pastures.
Technical Abstract: The objective of this research was to determine the effect of biochanin A (BCA), an isoflavone produced by red clover (Trifolium pratense L.), on corn fermentation by rumen microorganisms. When bovine rumen cell suspensions (n = 3) were incubated (24 h, 39 °C) with corn, amylolytic bacteria including group D Gram-positive cocci (GPC; Streptococcus bovis; enterococci) proliferated, cellulolytic bacteria were inhibited, lactate accumulated, and pH declined. Addition of BCA (30 µg mL-1) inhibited lactate production, and pH decline. BCA had no effect on total amylolytics, but increased lactobacilli and decreased GPC. The initial rate and total starch disappearance was decreased by BCA addition. BCA with added Strept. bovis HC5 supernatant (containing bacteriocins) inhibited all amylolytic bacteria tested (Strept. bovis JB1; Strept. bovis HC5; Lactobacillus reuteri, Selenemonas ruminatium) to a greater extent than either addition alone. BCA increased remaining cellulolytics and dry matter digestibility of hay with corn starch. These results indicate that BCA mitigates changes associated with corn fermentation by bovine rumen microorganisms ex vivo. Biochanin A could serve as an effective mitigation strategy for rumen acidosis.