In Vitro Evaluation of Different Dietary Methane Mitigation Strategies

Abstract

Simple Summary: Dietary methane mitigation strategies do not necessarily make food production from ruminants more energy-efficient, but reducing methane (CH 4 ) in the atmosphere immediately slows down global warming, helping to keep it within 2 • C above the pre-industrial baseline. There is no single most efficient strategy for mitigating enteric CH 4 production from domestic ruminants on forage-based diets. This study assessed a wide variety of dietary CH 4 mitigation strategies in the laboratory, to provide background for future studies with live animals on the efficiency and feasibility of dietary manipulation strategies to reduce CH 4 production. Among different chemical and plant-derived inhibitors and potential CH 4 -reducing diets assessed, inclusion of the natural antimethanogenic macroalga Asparagopsis taxiformis showed the strongest, and dose-dependent, CH 4 mitigating effect, with the least impact on rumen fermentation parameters. Thus, applying Asparagopsis taxiformis at a low daily dose was the best potential dietary mitigation strategy tested, with promising long-term effects, and should be further studied in diets for lactating dairy cows. Abstract:We assessed and ranked different dietary strategies for mitigating methane (CH 4 ) emissions and other fermentation parameters, using an automated gas system in two in vitro experiments. In experiment 1, a wide range of dietary CH 4 mitigation strategies was tested. In experiment 2, the two most promising CH 4 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 Asparagopsis taxiformis (AT) decreased predicted in vivo CH 4 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 4 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 4 emissions in vitro, and AT inclusion additionally showed a strong dose-dependent CH 4 mitigating effect, with the least impact on rumen fermentation parameters.

Seaweed and Seaweed Bioactives for Mitigation of Enteric Methane: Challenges and Opportunities

“…The greatest CH 4 mitigation potential was observed for the red seaweed A. taxiformis with almost complete inhibition in vitro with inclusion levels up to 16.7% of the organic matter (OM). A. taxiformis was highly effective in decreasing the production of CH 4 with a reduction of 99% at doses as low as 2% OM [ 45 , 46 , 47 , 48 ]. Machado et al [ 49 ] identified that bromoform was the main bioactive in A. taxiformis that promotes anti-methanogenic activity in in vitro studies.…”

Comparative Effects of Stovers of Four Varieties of Common Vetch on Growth Performance, Ruminal Fermentation, and Nutrient Digestibility of Growing Lambs

“…Improvement of forage efficiency and reduction of CH 4 emissions is of high importance to benefit the global eco-environment [12,13]. Based on the model of Moss et al [22], the C333A and CLJ3 stover diets would generate lower CH 4 emissions than the control, and CLJ1 and CLJ2 stover diets, due to differences in total VFA concentration and proportions of individual VFA.…”

“…Methane (CH 4 ) emission by ruminants is a significant contributing factor to the emerging global warming phenomenon [11][12][13]. In addition, enteric CH 4 formed by the fermented feed in the gastrointestinal tract of ruminant represents a loss of approximately 2-12% of gross energy (GE) intake [11].…”

Modelling the impact of the macroalgaeAsparagopsis taxiformison rumen microbial fermentation and methane production

“…Model calibration was performed using experimental data from an in vitro study assessing the dose-response impact of A. taxiformis on fermentation and methane production (Chagas et al ., 2019). In such a study, in vitro fermentation was carried out with rumen inoculum from two lactating Swedish Red cows.…”

“…Then, we used the generated files by IDEAS to look for global optimal solutions using the Matlab optimization toolbox MEIGO (Egea et al, 2014) that implements the enhanced scatter search method developed by (Egea et al, 2010) for global optimization. We reduced substantially the number of parameters to be estimated by setting most of the model parameters to the values reported in the original model implementation and using the information obtained from the in vitro study (Chagas et al, 2019). For example, the hydrolysis rate constant for NDF was obtained from (Chagas et al, 2019) whereas the hydrolysis rate constants of NSC ( hydr,nsc ) and proteins ( hydr,pro ) were included in the parameter estimation problem.…”