In Vitro Evaluation of Different Dietary Methane Mitigation Strategies

Abstract

We assessed and ranked different dietary strategies for mitigating methane (CH₄) emissions and other fermentation parameters, using an automated gas system in two in vitro experiments. In experiment 1, a wide range of dietary CH₄ mitigation strategies was tested. In experiment 2, the two most promising CH₄ 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 <i>Asparagopsis taxiformis</i> (AT) decreased predicted in vivo CH₄ 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 CH₄ 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 CH₄ emissions in vitro, and AT inclusion additionally showed a strong dose-dependent CH₄ mitigating effect, with the least impact on rumen fermentation parameters.