Effective use of Wolinella succinogenes for the augmentation of nitrate and nitrite reduction to suppress methane production in the rumen

In order to reduce methane production in the rumen, possibility to augment nitrate and nitrite reduction by stimulating the growth of Wolinella succinogenes was examined. W. succinogenes that was added to in vitro cultures of mixed ruminal microbes disappeared within 4h, but addition of nitrate prolonged the time to disappear. This result could be explained by the fact that W. succinogenes acquires energy by electron transport phosphorylation (ETP) coupled with nitrate and nitrite reduction. Addition of W. succinogenes to cultures of mixed ruminal microbes stimulated nitrate and nitrite reduction. Stimulation of nitrite reduction was greater, which decreased nitrite accumulation. As a result, the adverse effect of nitrite on overall fermentation was alleviated. Addition of nitrate and W. succinogenes greatly decreased methane production without suppressing overall fermentation. Addition of fumarate, in addition to nitrate, magnified the effects of W. succinogenes on nitrate and nitrite reduction and on methane production. This could be explained by the increased growth of W. succinogenes, because this bacterium acquires additional energy by ETP coupled with fumarate reduction. Stimulation of nitrate and nitrite reduction when W. succinogenes was added was greater than when other nitrate-reducing bacteria, such as Selenomonas ruminantium and Veillonella parvula, were added. In in vivo experiments with goats, addition of nitrate to a diet increased the number of W. succinogenes in the rumen. Addition of fumarate, in addition to nitrate, further increased the number of W. succinogenes. Activities of nitrate reductase and nitrite reductase per cell mass of total bacteria in the rumen were elevated by the addition of nitrate and fumarate, suggesting that the ability of the rumen ecosystem to reduce nitrate and nitrite was enhanced. Thus, feeding a diet containing nitrate and fumarate may be effective to stimulate the growth of W. succinogenes in the rumen.