Molecular characterization of ruminal microbes for the augmentation of nitrite reduction and for the supplession of methane emission

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The effects of dietary nitrate addition on ruminal fermentation characteristics and microbial populations in goats were investigated. Addition of nitrate resulted in a decrease in the total concentration of ruminal volatile fatty acids, an increase in the acetate:propionate ratio, and increases in the ammonia and lactate concentrations. Populations of methanogens, protozoa, and fungi were greatly decreased as a result of nitrate inclusion in the diet. There was modest or little impact of nitrate on the populations of prevailing species or genus of bacteria in the rumen, whereas Selenomonas ruminantium greatly increased. Quantification of the genes encoding nitrate reductase and nitrite reductase of S. ruminantium showed that these genes were increased by feeding nitrate, suggesting that the growth of nitrate- and nitrite-reducing S. ruminantium is stimulated by nitrate addition. Thus, S. ruminantium is likely to play a major role in nitrate and nitrite reduction in the rumen.