In Vitro Evaluation of Different Dietary Methane Mitigation Strategies.

We assessed and ranked different dietary strategies for mitigating methane (CH) emissions and other fermentation parameters, using an automated gas system in two in vitro experiments. In experiment 1, a wide range of dietary CH mitigation strategies was tested. In experiment 2, the two most promising CH inhibitory compounds from experiment 1 were tested in a dose-response study. In experiment 1, the chemical compounds 2-nitroethanol, nitrate, propynoic acid, p-coumaric acid, bromoform, and (AT) decreased predicted in vivo CH production (1.30, 21.3, 13.9, 24.2, 2.00, and 0.20 mL/g DM, respectively) compared with the control diet (38.7 mL/g DM). The 2-nitroethanol and AT treatments had lower molar proportions of acetate and higher molar proportions of propionate and butyrate compared with the control diet. In experiment 2, predicted in vivo CH production decreased curvilinearly, molar proportions of acetate decreased, and propionate and butyrate proportions increased curvilinearly with increased levels of AT and 2-nitroethanol. Thus 2-nitroethanol and AT were the most efficient strategies to reduce CH emissions in vitro, and AT inclusion additionally showed a strong dose-dependent CH mitigating effect, with the least impact on rumen fermentation parameters.