PSXIV-1 - In vitro evaluation of methane mitigation using monensin and ammonium nitrate in beef cattle diets

Currently, the use of feed additives appears as an alternative in reducing the environmental impact of animal agriculture, reducing the emission of greenhouse gases and increasing the acceptability of exports in international trade. Thus, the objective of the present study was to evaluate the in vitro rumen fermentation parameters by adding 4.5% ammonium nitrate and 30 ppm of the additive sodium monensin to beef cattle diets, searching for the best alternative to mitigate methane production. The experiment was performed in an in vitro gas production system, and the fermentation kinetics, methanogenesis and short-chain fatty acid (SCFA) production were studied. Regarding methanogenesis, it was observed that the diet with ammonium nitrate showed higher in vitro degradability in DM (P = 0.017) and lower methane production (in ml/g of DM; P = 0.0088), compared to the diet with sodium monensin. Considering the fermentation kinetics, it can be stated that acetate production in molar (%) was lower in control and monensin diets, and higher in nitrate and nitrate + monensin diets (P < 0.0001). It is concluded that both treatments ammonium nitrate + sodium monensin and ammonium nitrate alone have mitigating effect on methane emission, when compared to the control treatment. However, ammonium nitrate is more effective in this regard, producing less methane in vitro and having no negative effect on rumen fermentation parameters.