Explore the vast range of titles available.

Ruminant enteric methane, the largest agricultural source of CH₄, is a key target in global climate policies. We developed a biowaste-derived live fed microbial (LFM) from fruit- and vegetable residues and evaluated its potential as a scalable intervention to reduce enteric methane while improving animal performance. In controlled in vitro assays and a 98 days in vivo feeding trial in bovine calves ( n  = 15), LFM at 2% dietary inclusion (dry-matter basis) improved feed efficiency by 30.9%, reduced modelled methane emissions by 25.2%, increased total volatile fatty acids by 45.5%, and lowered NH₃–N by 28.4%. At 3% inclusion, feed efficiency improved by 25.5%, methane emissions decreased by 30.4%, total VFA increased by 43.0%, and NH₃–N declined by 11.7%. Methane abatement was estimated by integrating in vitro and in vivo measurements using an empirically fitted conversion factor and Tier-2–compatible intake models. The IPCC (2006) Tier-2 equivalents indicated ~19% reduction. Scaling to India’s livestock herd suggested abatement of 15.4 Mt CH₄ yr⁻¹ (432.3 Mt CO₂-eq yr⁻¹; GWP₁₀₀ = 28) under full adoption, corresponding to ~US$494.1 million annually under the carbon-price assumption used. These findings position biowaste-derived LFM as a circular-economy feed technology capable of simultaneously improving productivity and reducing enteric methane emissions at scale.

Molecular hydrogen (H2) and formate (HCOO−) are metabolic end products of many primary fermenters in the rumen ecosystem. Both play a vital role in fermentation where they are electron sinks for individual microbes in an anaerobic environment that lacks external electron acceptors. If H2 and/or formate accumulate within the rumen, the ability of primary fermenters to regenerate electron carriers may be inhibited and microbial metabolism and growth disrupted. Consequently, H2- and/or formate-consuming microbes such as methanogens and possibly homoacetogens play a key role in maintaining the metabolic efficiency of primary fermenters. There is increasing interest in identifying approaches to manipulate the rumen ecosystem for the benefit of the host and the environment. As H2 and formate are important mediators of interspecies interactions, an understanding of their production and utilization could be a significant starting point for the development of successful interventions aimed at redirecting electron flow and reducing methane emissions. We conclude by discussing in brief ruminant methane mitigation approaches as a model to help understand the fate of H2 and formate in the rumen ecosystem.

Practices such as selecting high-quality feed, intensive housing, use of rotational grazing to sequester carbon in the soil, increasing diet digestibility (5), selecting the type of carbohydrates in the diet, increasing reproductive efficiency, and breeding for higher productivity, have been proposed to reduce emission intensity and improve animal health and welfare (Figure 1). Propionic acid is the only volatile fatty acid with gluconeogenic activity and the potential to improve the efficiency of metabolizable energy utilization in the whole animal (8). [...]the alternative strategies include the induction of changes in the ruminal microbiome, which can be through the inclusion of plants containing secondary metabolites (4), the direct addition of essential oils, or the inclusion of red algae species. [...]all the strategies outlined above must support sustainability (for people, planet, and profitability) and ethics in order to be more environmentally friendly, and we must examine the consequences of current and future strategies for animal welfare and contrast them with their effectiveness in mitigating climate change.

The latter is expressed either through traditional indicators such as the conversion rate and weight gain or through the carbon footprint. [...]the search for comprehensive strategies to mitigate GHG emissions from livestock systems must incorporate strategies associated with animal feed and nutrition and ultimately evaluate their effect through productive parameters. Moringa oleifera is commonly used for its protein content; however, its inclusion has also been related to a decrease in methane production. [...]the incorporation of leaves, flour, seeds, or extracts of Moringa oleifera, thanks to the natural capacity of the species to inhibit methanogenesis, has reported successful results in research carried out in buffalos (6), goats (7), beef cattle (8), and dairy cows (9). Through his Perspective article,Vijn et al.consider the use of seaweed and provides valuable recommendations for the design of research associated with the use of seaweed as an enteric methane mitigant in the stages of seaweed production, animal feed production, and livestock production.Ku-Vera et al.perform an exhaustive review on the role of secondary plant metabolites on enteric methane mitigation, explaining the possible mechanisms of action of tannins, saponins, essential oils, flavonoids on enteric CH4 mitigation. [...]Toro-Mujica, using the results of previous research about the effect of the use of additives in the production of GHG, raises the need for evaluation at the livestock system level.

Significance Agricultural methane emissions must be decreased by 11 to 30% of the 2010 level by 2030 and by 24 to 47% by 2050 to meet the 1.5 °C target. We identified three strategies to decrease product-based methane emissions while increasing animal productivity and five strategies to decrease absolute methane emissions without reducing animal productivity. Globally, 100% adoption of the most effective product-based and absolute methane emission mitigation strategy can meet the 1.5 °C target by 2030 but not 2050, because mitigation effects are offset by projected increases in methane. On a regional level, Europe but not Africa may be able to meet their contribution to the 1.5 °C target, highlighting the different challenges faced by high- and middle- and low-income countries.

The goal of this review was to analyze published data related to mitigation of enteric methane (CH4) emissions from ruminant animals to document the most effective and sustainable strategies. Increasing forage digestibility and digestible forage intake was one of the major recommended CH4 mitigation practices. Although responses vary, CH4 emissions can be reduced when corn silage replaces grass silage in the diet. Feeding legume silages could also lower CH4 emissions compared to grass silage due to their lower fiber concentration. Dietary lipids can be effective in reducing CH4 emissions, but their applicability will depend on effects on feed intake, fiber digestibility, production, and milk composition. Inclusion of concentrate feeds in the diet of ruminants will likely decrease CH4 emission intensity (Ei; CH4 per unit animal product), particularly when inclusion is above 40% of dietary dry matter and rumen function is not impaired. Supplementation of diets containing medium to poor quality forages with small amounts of concentrate feed will typically decrease CH4 Ei. Nitrates show promise as CH4 mitigation agents, but more studies are needed to fully understand their impact on whole-farm greenhouse gas emissions, animal productivity, and animal health. Through their effect on feed efficiency and rumen stoichiometry, ionophores are likely to have a moderate CH4 mitigating effect in ruminants fed high-grain or mixed grain-forage diets. Tannins may also reduce CH4 emissions although in some situations intake and milk production may be compromised. Some direct-fed microbials, such as yeast-based products, might have a moderate CH4-mitigating effect through increasing animal productivity and feed efficiency, but the effect is likely to be inconsistent. Vaccines against rumen archaea may offer mitigation opportunities in the future although the extent of CH4 reduction is likely to be small and adaptation by ruminal microbes and persistence of the effect is unknown. Overall, improving forage quality and the overall efficiency of dietary nutrient use is an effective way of decreasing CH4 Ei. Several feed supplements have a potential to reduce CH4 emission from ruminants although their long-term effect has not been well established and some are toxic or may not be economically feasible.

The growing demand for sustainable animal production is compelling researchers to explore the potential approaches to reduce emissions of greenhouse gases from livestock that are mainly produced by enteric fermentation. Some potential solutions, for instance, the use of chemical inhibitors to reduce methanogenesis, are not feasible in routine use due to their toxicity to ruminants, inhibition of efficient rumen function or other transitory effects. Strategies, such as use of plant secondary metabolites and dietary manipulations have emerged to reduce the methane emission, but these still require extensive research before these can be recommended and deployed in the livestock industry sector. Furthermore, immunization vaccines for methanogens and phages are also under investigation for mitigation of enteric methanogenesis. The increasing knowledge of methanogenic diversity in rumen, DNA sequencing technologies and bioinformatics have paved the way for chemogenomic strategies by targeting methane producers. Chemogenomics will help in finding target enzymes and proteins, which will further assist in the screening of natural as well chemical inhibitors. The construction of a methanogenic gene catalogue through these approaches is an attainable objective. This will lead to understand the microbiome function, its relation with the host and feeds, and therefore, will form the basis of practically viable and eco-friendly methane mitigation approaches, while improving the ruminant productivity.

Anthropomorphic greenhouse gases are raising the temperature of the earth and threatening ecosystems. Since 1950 atmospheric carbon dioxide has increased 28%, while methane has increased 70%. Methane, over the first 20 years after release, has 80-times more warming potential as a greenhouse gas than carbon dioxide. Enteric methane from microbial fermentation of plant material by ruminants contributes 30% of methane released into the atmosphere, which is more than any other single source. Numerous strategies were reviewed to quantify their methane mitigation potential, their impact on animal productivity and their likelihood of adoption. The supplements, 3-nitrooxypropanol and the seaweed, Asparagopsis, reduced methane emissions by 40+% and 90%, respectively, with increases in animal productivity and small effects on animal health or product quality. Manipulation of the rumen microbial population can potentially provide intergenerational reduction in methane emissions, if treated animals remain isolated. Genetic selection, vaccination, grape marc, nitrate or biochar reduced methane emissions by 10% or less. Best management practices and cattle browsing legumes, Desmanthus or Leucaena species, result in small levels of methane mitigation and improved animal productivity. Feeding large amounts daily of ground wheat reduced methane emissions by around 35% in dairy cows but was not sustained over time.

Quantifying sector‐resolved methane fluxes in complex emissions environments is challenging yet necessary to improve emissions inventories and guide policy. Here, we separate energy and agriculture sector emissions using a dynamic linear model analysis of methane, ethane, and ammonia data measured at a Northern Colorado site from November 2021 to January 2022. By combining these sector‐apportioned observations with spatially resolved inventories and Bayesian inverse methods, energy and agriculture methane fluxes are optimized across the study's ∼850 km2 sensitivity area. Energy sector fluxes are synthesized with previous literature to evaluate trends in energy sector methane emissions. Optimized agriculture fluxes in the study area were 3.5× larger than inventory estimates; we demonstrate this discrepancy is consistent with differences in the modeled versus real‐world spatial distribution of agricultural sources. These results highlight how sector‐apportioned methane observations can yield multi‐sector inventory optimizations in complex environments. Plain Language Summary Improving our knowledge of the locations, magnitudes, and types of methane sources is important for implementing effective emissions mitigation technologies and regulations. Methane emissions are often challenging to quantify because a wide variety of sources can emit methane, and these disparate sources are often intermingled. We demonstrate how a dynamic linear model can use multi‐month time series of two tracer gases, ethane and ammonia, to effectively separate methane emissions from the energy and agriculture sectors. Incorporating these data into a Bayesian inverse analysis refines the magnitude and distribution of methane fluxes from each sector. Our analysis reveals that methane from agriculture is several times higher than inventory estimates. While this is in part due to the spatial distribution of sources, more monitoring is needed to improve agriculture emissions factors. Energy sector emissions factors optimized in this work are consistent with other regional studies of energy sector methane emissions. A synthesis of these works demonstrates a regional decline in energy sector emissions despite a concomitant increase in oil and gas extraction; however, current emissions are similar to 2008 estimates. Key Points A dynamic linear model apportions energy and agriculture methane emissions from multi‐month trace gas measurements in Northern Colorado An estimated 0.4 ± 0.2 kg CH4 are emitted per barrel of oil equivalent produced, yielding a Wattenberg Field emission rate of 15 Mg CH4/hr Optimized agriculture methane emissions are higher than inventory predictions, in part due to mislocated fluxes in the inventory

Background Enteric methane emissions from dairy cows are an environmental problem as well as a gross feed energy loss to the animal. Methane is generated in the rumen by methanogenic archaea from hydrogen (H 2 ) + carbon dioxide and from H 2 + methanol or methylamines. The methanogenic substrates are provided by non-methanogens during feed fermentation. Methane mitigation approaches have yielded variable results, partially due to an incomplete understanding of the contribution of hydrogenotrophic and methylotrophic archaea to methanogenesis. Research indicates that 3-nitrooxypropanol (3-NOP) reduces enteric methane formation in dairy cows by inhibiting methyl-coenzyme M reductase (MCR), the enzyme responsible for methane formation. The purpose of this study was to utilize metagenomic and metatranscriptomic approaches to investigate the effect of 3-NOP on the rumen microbiome and to determine the fate of H 2 that accumulates less than expected under inhibited methanogenesis. Results The inhibitor 3-NOP was more inhibitory on Methanobrevibacter species than methanol-utilizing Methanosphaera and tended to reduce the gene expression of MCR. Under inhibited methanogenesis by 3-NOP, fluctuations in H 2 concentrations were accompanied by changes in the expression of [FeFe] hydrogenases in H 2 -producing bacteria to regulate the amount of H 2 production. No previously reported alternative H 2 sinks increased under inhibited methanogenesis except for a significant increase in gene expression of enzymes involved in the butyrate pathway. Conclusion By taking a metatranscriptomic approach, this study provides novel insights on the contribution of methylotrophic methanogens to total methanogenesis and regulation of H 2 metabolism under normal and inhibited methanogenesis by 3-NOP in the rumen. -iX6YPbp4qKjzQQ25nvbCQ Video Abstract