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 CH 4 production, but also decreased net CO 2 production and increased net H 2 production. Total VFA concentration was lower (p<0.05) for NND than TND. Suppression of CO 2 production and total VFA concentration may be linked to increased concentration of H 2 . 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.