The objective of this study was to investigate the effects of ethyl nitroacetate, ethyl 2-nitropropionate and 3-nitropropionic acid on ruminal production of CH4, H2, volatile fatty acids (VFAs) and on dry matter digestibility of ground alfalfa under in vitro conditions. In vitro incubations were conducted as consecutive batch cultures. Total gas and amounts of methane produced by ruminal microbes were decreased by all nitrocompounds (P < 0.05). Total production of VFAs was significantly reduced for all the nitrocompounds (P < 0.05) except for NPA. DM disappearance was not affected (P >0.05) by treatment.

This study aimed to evaluate the effect of three yeast strains, Pichia guilliermondii (Levica 27), Candida norvegensis (Levazoot 15), and a commercial product (Levucell® SC 10) containing Saccharomyces cerevisiae, on in vitro rumen fermentation of two substrates: corn stover and a total mixed ration (TMR). Samples were taken 24 hours post-fermentation to measure pH, ammonia nitrogen (NH3-N), gas production, and volatile fatty acid (VFA) concentrations. The addition of yeasts did not affect gas production at 24 hours for either diet. For pH, differences between yeast strains were noted when TMR was used. The lowest NH3-N concentration (6.1 mM) was recorded with corn stover, showing similar results across strains. Conversely, NH3-N levels with TMR ranged from 47 mM to 66 mM. The inclusion of all three yeast strains increased the molar concentrations of total VFA, as well as acetic (C2), propionic (C3), and butyric (C4) acids in the rumen fluid. The C2:C3 ratio remained unchanged with corn stover but decreased with the inclusion of Levica 27 and Levazoot 15 in the TMR. With the commercial product Levucell® SC 10, this ratio was comparable to the control treatment. In conclusion, Levica 27 and Levazoot 15 demonstrated a stimulatory effect on in vitro rumen fermentation for the evaluated diets, evidenced by increased VFA concentrations.