Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/3/2016
Publication Date: 12/8/2016
Citation: Harlow, B.E., Flythe, M.D., Kagan, I., Aiken, G.E. 2016. Biochanin A (an isoflavone produced by red clover) promotes weight gain of steers grazed in mixed grass pastures and fed dried-distillers grains. Crop Science. 57:506-514.
Interpretive Summary: Hyper-ammonia producing bacteria in the rumens of cattle are responsible for breaking down protein and producing ammonia that is eventually excreted by the cattle and has a negative impact on the environment. Red clover produces an isoflavone compound, biochanin A, that can inhibit the hyper-ammonia bacteria, which increases the quality of protein available to cattle for digestion and reduces amounts of ammonia produced in the rumen. From a laboratory study, we found that adding dried distiller’s grains to cattle rumen fluid increased hyper-ammonia producing bacteria and ammonia concentrations, but addition of biochanin A to the rumen fluid resulted in 100-fold fewer hyper-ammonia bacteria and 37% less ammonia. A grazing experiment with steers grazing a mixture of cool-season grasses found a 15% increase in average daily weight gain by feeding dried distiller’s grains, but there was a 29% increase in average daily gain by adding biochanin A to the dried distiller’s grains. These results clearly demonstrated the value to cattle production and reduction in environmental impact when red clover is planted and maintained in grass pastures.
Technical Abstract: Biochanin A (BCA) is an isoflavone produced by red clover (Trifloium pratense L.) that can inhibit hyper-ammonia producing bacteria (HAB) to reduce deamination in the rumen and increase the feed amino acids available for gastric digestion. An in vitro experiment was conducted to evaluate the effect of dried distiller’s grains (DDG) and BCA on HAB in bovine rumen fluid. Following a 24-h incubation, HAB and ammonia concentrations in the basal media increased with addition of DDG. However, DDG fermentations with BCA had 100-fold fewer HAB and 37% less ammonia than DDG only fermentations. A grazing experiment was conducted with crossbred steers (Bos taurus) grazing a mixture of endophyte-free tall fescue [Lolium arundinaceum (Schreb.) Darbysh], Kentucky bluegrass (Poa pratense L.) and orchardgrass (Dactylis glomerata L.) in the early- and late-growing season. Average daily gains (ADG) were compared among treatments of pasture-only control, daily feeding of 1.4 kg DDG steer-1, and daily feeding of 1.4 kg DDG plus BCA (6.3 g steer-1). Averaged over the early- and late-grazing seasons, feeding DDG increased ADG by 15 percent over the pasture-only treatment, but addition of BCA to the DDG provided a stronger increase in ADG of 29 percent over the control treatment. Results of the ex vivo and grazing experiments provide evidence that BCA inhibits HAB in the rumen and that the reduced deamination in the rumen can enhance weight gain performance of steers.