Use of Nitrate-nitrogen as a Sole Dietary Nitrogen Source to Inhibit Ruminal Methanogenesis and to Improve Microbial Nitrogen Synthesis In vitro

An in vitro study was conducted to determine the effect of nitrate-nitrogen used as a sole dietary nitrogen source on ruminal fermentation characteristics and microbial nitrogen (MN) synthesis. Three treatment diets were formulated with different nitrogen sources to contain 13% CP and termed i) nitrate-N diet (NND), ii) urea-N diet (UND), used as negative control, and iii) tryptone-N diet (TND), used as positive control. The results of 24-h incubations showed that nitrate-N disappeared to background concentrations and was not detectable in microbial cells. The NND treatment decreased net CH4 production, but also decreased net CO2 production and increased net H2 production. Total VFA concentration was lower (p<0.05) for NND than TND. Suppression of CO2 production and total VFA concentration may be linked to increased concentration of H2. The MN synthesis was greater (p<0.001) for NND than UND or TND (5.74 vs. 3.31 or 3.34 mg/40 ml, respectively). Nitrate addition diminished methane production as expected, but also increased MN synthesis. (