Methane Inhibitor Research Articles

Mitigating methane emissions in grazing beef cattle with a seaweed-based feed additive: Implications for climate-smart agriculture

The ruminant livestock sector considerably contributes to global greenhouse gas emissions. This study investigates the effectiveness of pelleted bromoform-containing seaweed ( Asparagopsis taxiformis ) (Brominata) as an enteric methane (CH 4 ) inhibitor in grazing beef cattle. The primary objective was to assess the impact of this antimethanogenic additive on enteric CH 4 emissions under real-world farm conditions. Twenty-four beef steers, crossbreeds of Wagyu and Angus, with an average liveweight of 399 ± 21.7 kg, were allocated to two treatment groups: Control and Brominata. These animals underwent regular weigh-ins every 14 d, and measurements of CH 4 , carbon dioxide (CO 2 ), and hydrogen (H 2 ) emissions were conducted using the GreenFeed system. Statistical analysis was conducted using SAS 9.4, wherein the model incorporated fixed effects for treatment, time, their interaction, and a covariate, while accounting for animal variations as a random effect within each phase. Three phases of bromoform intake were identified: a 3-wk ramp-up phase, a 3-wk optimal phase, and a 2-wk decreasing phase. No differences were observed between the weekly initial and final liveweight, average daily gain, and predicted dry matter intake. During optimal and decreasing phases, average enteric CH 4 emissions were significantly reduced in steers that received Brominata supplementation compared to those without supplementation (115 vs. 185 g/d, respectively). Additionally, both groups had similar CO 2 emissions (6.8 vs. 7.2 kg/d), while H 2 emissions were lower in the control group (3.4 vs. 1.8 g/d). The findings suggest that pelleted bromoform-containing feed additive has the potential to reduce enteric CH 4 emissions from grazing beef cattle.

Polyphenol rewiring of the microbiome reduces methane emissions.

Methane mitigation is regarded as a critical strategy to combat the scale of global warming. Currently, about 40% of methane emissions originate from microbial sources, which is causing strategies to suppress methanogens, either through direct toxic effects or by diverting their substrates and energy, to gain traction. Problematically, current microbial methane mitigation knowledge derives from rumen studies and lacks detailed microbiome-centered insights, limiting translation across ecosystems. Here we utilize genome-resolved metatranscriptomes and metabolomes to assess the impact of a proposed methane inhibitor, catechin, on greenhouse gas emissions for high-methane-emitting peatlands. In microcosms, catechin drastically reduced methane emissions by 72-84% compared to controls. Longitudinal sampling allowed for reconstruction of a novel catechin degradation pathway involving Actinomycetota and Clostridium, which break down catechin into smaller phenolic compounds within the first 21 days, followed by degradation of phenolic compounds by Pseudomonas_E from days 21 to 35. These genomes also co-expressed hydrogen-uptake genes, suggesting that hydrogenases may act as a hydrogen sink during catechin degradation, depriving methanogens of substrates. This was supported by decreased gene expression in hydrogenotrophic and hydrogen-dependent methylotrophic methanogens under catechin treatment. We also saw reduced gene expression from genomes inferred to be functioning syntrophically with hydrogen-utilizing methanogens. We propose that catechin metabolic redirection effectively starves hydrogen-utilizing methanogens, offering a potent avenue for curbing methane emissions across diverse environments including ruminants, landfills, and constructed or managed wetlands.

Metagenomic insights into the mechanistic differences of plant polyphenols and nitrocompounds in reducing methane emissions using the rumen simulation technique

Methane (CH4) emissions from ruminants contribute significantly to greenhouse gas levels and also result in considerable feed energy losses. Plant polyphenols and nitrocompounds are two typical types of methane inhibitors. The study investigates the mechanistic differences between 2-nitroethanol (NE) and proanthocyanidins (PAC) in reducing methane emissions from ruminant livestock using the rumen simulation technique (RUSITEC) combined with metagenomic analyses.The experiment was performed as a complete randomized block design with 3 runs. Run was used as a blocking factor. The treatments included a control (CON) with no additive, NE at 0.5 g/kg dry matter (DM), and PAC at 20 g/kg DM, all incubated in vitro for 24 h (h) with eight replicates per treatment. The results showed that NE significantly reduced CH4 production by 94.9 % (P < 0.01) and total volatile fatty acid (TVFA) concentration by 11.1 % (P < 0.05) compared to the control. NE also decreased the acetate-to-propionate ratio (A/P) from 1.93 to 1.60 (P < 0.01), indicating a shift towards more efficient fermentation. In contrast, PAC reduced methane production by 11.7 % (P < 0.05) and decreased the A/P (P < 0.05) while maintaining microbial diversity and fermentation stability, with no significant impact on TVFA concentration (P > 0.05). Metagenomic analysis revealed that NE markedly suppressed the abundance of key genera involved in carbohydrate metabolism, including Prevotella and Bacteroides, leading to reduced acetate and butyrate pathways. NE also selectively inhibited methanogenic archaea, particularly Methanobrevibacter spp., which are integral to the hydrogenotrophic pathway (P < 0.01). On the other hand, PAC showed selective inhibition of Methanosphaera spp., targeting the methylotrophic pathway (P < 0.01). These findings provide valuable insights into the distinct microbial and metabolic pathways modulated by NE and PAC, offering potential strategies for developing effective dietary interventions to mitigate methane emissions in ruminant livestock.

Predicting future adoption of early-stage innovations for smart farming: A case study investigating critical factors influencing use of smart feeder technology for potential delivery of methane inhibitors in pasture-grazed dairy systems

Globally, livestock farmers are challenged with reducing greenhouse gas emissions to mitigate climate change. A potential option for pasture-based dairy farmers involves including methane-inhibiting compounds in the diet. A novel approach to deliver these compounds with the required frequency and precision is via smart-feeders, an existing smart farming technology used to feed supplements automatically to animals in-paddock. For this innovation to be successful, however, it must integrate with farm systems and provide farmers with a positive value proposition. The aim of this study was to examine the farm system and technology factors influencing potential uptake of in-paddock smart technologies for delivering methane inhibitors in pasture-grazed systems. We utilized an adoption prediction tool (ADOPT) to model the adoption outcomes of smart-feeders as methane inhibitor delivery mechanisms on dairy farms, with input from industry experts and farmers via focus groups. The results indicated low adoption of smart-feeders in a pasture-based system context. This was further explored with a sensitivity analysis of seven critical ADOPT factors which were identified as influential through the farmer focus groups. We modelled the impact of the seven critical ADOPT factors for two smart-feeder concepts to evaluate their relative adoption potential. The adoption modelling showed that while factors such as technology cost and function were important, adoption would also be highly influenced by future regulation settings, innovation uncertainty, and the alignment with farmer values and worldviews about their farm system. This research highlighted that in-paddock delivery technology, and processes for its use on-farm, represents an early-stage innovation and therefore is vital that farmers and other stakeholders are involved in further development to ensure adoption factors are addressed.

The role of monoammonium glycyrrhizinate as a methane inhibitor to limit the rumen methane emissions of Karakul sheep

Methane (CH4) from ruminant production systems produces greenhouse gases that contribute to global warming. Our goal was to determine whether monoammonium glycyrrhizinate could inhibit CH4 emissions over the long term without affecting animal performance and immune indices in Karakul sheep. This study aimed to assess the effects of medium−term (60 days) addition of monoammonium glycyrrhizinate on growth performance, apparent digestibility, CH4 emissions, methanogens, fibre-degrading bacteria and blood characteristics in Karakul sheep. Twelve male Karakul sheep (40.1 ± 3.59 kg) with fistula were randomly divided into two groups (n = 6): the Control group received a basal diet + the same volume of distilled water (30 ml) and the Treatment group received a basal diet + 8.75 g/kg monoammonium glycyrrhizinate injected via fistula. The adaptation stage was 15 days, and the measurement stage was 60 days. The sampling during the measurement stage was divided into two stages, stage I (1 ∼ 30 d) and stage II (31 ∼ 60 d). The results showed that monoammonium glycyrrhizinate significantly reduced the relative abundance of Bacteroides caccae, daily CH4 emission and protozoa population, significantly increased the relative abundance of Lachnospiraceae bacterium AD3010, Lachnospiraceae bacterium FE2018, Lachnospiraceae bacterium NK3A20, Lachnospiraceae bacterium NK4A179 and Lachnospiraceae bacterium V9D3004 in stage I (P < 0.05); significantly increased the relative abundance of Lachnospiraceae bacterium AD3010, but significantly decreased the relative abundance of Lachnospiraceae bacterium NK4A179 and Lachnospiraceae bacterium C6A11 in stage II (P < 0.05). Therefore, monoammonium glycyrrhizinate could be used as a CH4 inhibitor to limit the rumen CH4 emissions of Karakul sheep in short−term period (30 days) without affecting the growth performance, fibre digestibility and blood parameters.

Carbon footprint research and mitigation strategies for rice-cropping systems in China: a review

Reducing greenhouse gas (GHG) emissions and quantifying the carbon footprint (CF) of rice-cropping systems in the context of food security is an important step toward the sustainability of rice production. Exploring the key factors affecting emission reduction in rice production is important to properly evaluate the impact of China’s rice-cropping systems on global climate change. This review provides an overview of the direct and indirect CF in rice-cropping systems; analyzes the influencing factors in terms of rice-based cropping systems, varieties and agronomic practices; and proposes mitigation strategies. Different studies have shown that direct and indirect GHG emissions in rice-based cropping systems accounted for 38.3 to 95.5% and 4.5 to 61.7% of total emissions, respectively. And the CFs of ratoon rice, rice–wheat, rice–maize, rice–rapeseed, and rice–fish systems ranged from 316,9 kg CO2-eq kg−1 to 258,47 kg CO2-eq kg−1, which are lower than that in a double-rice planting system. High-yielding rice, drought-resistant rice, and other hybrids can mitigate GHG emissions from paddy fields by 3.7 ~ 21.5%. Furthermore, organic matter, water, tillage, straw incorporation, conservation tillage, reduced nitrogen fertilizer use, and added biochar and methane inhibitors could reduce emissions. Therefore, through reasonable agronomic measures, variety selection and optimal layout of rice-based rotation systems, the carbon neutral rate of rice production can be improved to help the national carbon sequestration and emission reduction target.

16S amplicon sequencing and untargeted metabolomics reveal changes in rumen microorganisms and metabolic pathways involved in the reduction of methane by cordycepin

As a major contributor to methane production in agriculture, there is a need for a suitable methane inhibitor to reduce ruminant methane emissions and minimize the impact on the climate. This work aimed to explore the influence of cordycepin on rumen fermentation, gas production, microbiome and their metabolites. A total of 0.00, 0.08, 0.16, 0.32, and 0.64 g L-1 cordycepin were added into fermentation bottles containing 2g total mixed ration for in vitro ruminal fermentation, and then the gas produced and fermentation parameters were measured for each bottle. Samples from the 0.00 and 0.64 g L-1 cordycepin addition were selected for 16S rRNA gene sequencing and metabolome analysis. The result of this experiment indicated that the addition of cordycepin could linearly increase the concentration of total volatile fatty acid, ammonia nitrogen, the proportion of propionate, valerate, and isovalerate, and linearly reduce ruminal pH and methane, carbon dioxide, hydrogen and total gas production, as well as the methane proportion, carbon dioxide proportion and proportion of butyrate. In addition, there was a quadratic relationship between hydrogen and cordycepin addition. At the same time, the relative abundance of Succiniclasticum, Prevotella, Rikenellaceae_RC9_gut_group, NK4A214_group, Christensenellaceae_R_7_group, unclassified_F082, Veillonellaceae_UCG_001, Dasytricha, Ophryoscolex, Isotricha, unclassified_Eukaryota, Methanobrevibacter, and Piromyces decreased significantly after adding the maximum dose of cordycepin. In contrast, the relative abundance of Succinivibrio, unclassified_Succinivibrionaceae, Prevotellaceae_UCG_001, unclassified_Lachnospiraceae, Lachnospira, Succinivibrionaceae_UCG_002, Pseudobutyrivibrio, Entodinium, Polyplastron, unclassified_Methanomethylophilaceae, Methanosphaera, and Candidatus_Methanomethylophilus increased significantly. Metabolic pathways such as biosynthesis of unsaturated fatty acids and purine metabolism and metabolites such as arachidonic acid, adenine, and 2′-deoxyguanosine were also affected by the addition of cordycepin. Based on this, we conclude that cordycepin is an effective methane emission inhibitor that can change the rumen metabolites and fermentation parameters by influencing the rumen microbiome, thus regulating rumen methane production. This experiment may provide a potential theoretical reference for developing Cordyceps byproduct or additives containing cordycepin as methane inhibitors.

ENTERIC METHANE PRODUCTION IN RUMINANTS: ITS EFFECT ON GLOBAL WARMING AND MITIGATION STRATEGIES-A REVIEW

Anthropic activities produce around 2/3 share of the total methane emission in the world, with the livestock sector being the primary contributor. Methane is a potent greenhouse gas, exhibiting a warming effect more than 21 times that of carbon dioxide, and is produced by microbes called methanogens during anaerobic fermentation. The release of methane from ruminants indicating a loss of feed energy that has the potential to elevate production. Economic and population growth will increase milk and meat demand, increasing CH4 production from the livestock sector. Various approaches including feed manipulation, supplementation of feed additives, management practices, genetic selection and vaccinations all were aimed at mitigating CH4 from the livestock sector. These measures change the composition of rumen and alter the working of methane-producing microbes. The addition of feed additives reduces the CH4 emission but human well-being limits their usage. Methane inhibitors, like those with a hydrogen sink property that has no adverse effects on rumen microbe populations, are considered ideal for reducing emissions. Research also shows that methane emission is a heritable and repeatable trait and that genomic and genetic traits present a considerable opportunity to minimize methane emissions from ruminants the accuracy of methane measurements is crucial and attention to background information in publications regarding measurement context and methods is necessary for comprehensive interpretation of results. Each method for measuring methane emissions from livestock has limitations tied to its original intent of use. Standardization within and between techniques, especially in respiration chambers, SF6 and Greenfeed Emission Monitoring System, can enhance result reliability. However, using these technologies beyond their intended purpose is risky, and extrapolating estimations may lead to unintended consequences. Combining different methods may offer the most comprehensive approach, but further research is needed to validate and compare individual methods, especially in wide-ranging production systems and to develop standardization protocols.

Pengaruh Pre-Treatment Kimia dan Biologi Terhadap Produksi Biogas dari Kulit Kopi

Coffee, as a major commodity in Indonesia, produces a huge number of byproducts and residues during the processing process. Coffee wastes and byproducts produced during coffee berry processing are a major source of contamination and represent significant environmental challenges in the coffee production process. One promising alternative in utilizing coffee wastes is converting into energy source i.e, of biogas from coffee pulp. Coffee pulp has toxic components that act as a methane inhibitor; these type of biomass have a problem with the lignin degradation process, which binds cellulose and hemicellulose. The use of cow's rumen fluid for methane production from coffee pulp is still rare, particularly for rumen fluid. Chemical pretreatment was carried out using alkali-peroxide followed by rumen fluid pretreatment. The performance of biogas produced from coffee pulp (with and without pretreatment) using rumen fluid as an inoculum has been investigated. Biogas was produced in a semi-batch reactor with a working volume of 2 liters for 30 days. Removal lignin, SS, VFA, and biogas yield were measured. This study aims to determine the biogas production from coffee pulp using variation HRT 20 and 30 days. It can be concluded that chemical pretreatment of NaOH - H2O2 combination can reduce lignin up to 75.02%. The volume of biogas produced increased with chemical pretreatment and rumen fluid as compared to the substrate with only rumen pretreatment According to Gas Chromatography analysis, the methane gas obtained from chemical pretreatment and rumen with HRT 30 days is 47.93%, while the methane obtained from rumen pretreatment with HRT 30 days is 34.28%.

Evaluation of several macroalgae species on methane emission and antioxidant activity based on in vitro rumen fermentation characteristics

Marine macroalgae are the prospective and promising Indonesian natural resources containing bioactive compounds. This study aimed at evaluating various seaweed species with optimal biological activity to mitigate in vitro rumen methane emission and to confirm their antioxidant properties. In addition, relationships among several phenolic fractions and methane (CH4) production of seaweeds were elucidated by Pearson Correlation to screen seaweeds for their capacity to reduce CH4 formation. For in vitro batch cultures experiment, the diets were 500 mg of a substrate of seaweed. They were incubated with 50 ml of buffered rumen fluid (1:2 ratio of rumen fluid to buffer media) in a 100 ml serum vial at 39°C for 72 hours incubation time. A randomized block design was carried out with 14 dried seaweed treatments and 5 different cattle rumen fluid groups as a block. For total phenol, flavonoid, and antioxidant activity, a completely randomized design with 14 treatments and 3 replications was carried out. Data were analyzed by Analysis of Variance (ANOVA) and Duncan analysis. The results showed that the lowest methane production (ml/g DM incubated) significantly (P<0.05) was reduced by Halymenia sp. (0.24) and Caulerpa racemosa (0.41). Caulerpa racemosa showed high flavonoid content (1.5 mg Quercetin/g) and Ulva lactuca had the highest phenol content (0.55 mg Gallic Acid/g). Gracilaria coronopifolia had strong antioxidant activity DPPH radical scavenging activity (77.5% inhibition). It was concluded that Halymenia sp., Caulerpa racemosa and Gracilaria coronopifolia could be used as methane inhibitors and antioxidants for ruminants.

Farm-level cost-effectiveness analysis of in-paddock feeding of methane inhibitors in pasture-based dairy

Various approaches have been proposed to reduce methane emissions from ruminant livestock systems. While methane-inhibiting feed-additives are not yet commercially available in New Zealand, it has been reported that they can reduce enteric methane emissions by 30-90% when fed to ruminant livestock regularly and precisely in total mixed ration systems. This study aims to determine the primary economic performance drivers of using In-Paddock Smart-Feeders (IPSF) for delivering methane inhibitors in pasture-based dairy to understand the conditions in which they are viable. A farm-level financial model is developed, drawing on the Economic Farm Survey produced by DairyNZ. Both a scenario and sensitivity analysis are conducted on the cost-effectiveness of the approach for methane mitigation. The main finding is that the largest cost associated with the approach is the cost of additionalsupplement, which would acts as a carrier for the methane inhibitor. Therefore, the quantity of additional supplement used prior to adoption is a key determinant of viability. There is a large range in breakeven methane prices depending on the value of assumptionsused. More certainty in these assumptions is required to fully understand the potential use of IPSFs to deliver methane-inhibiting feed-additives in-paddock.

Survival of Campylobacter jejuni during in vitro culture with mixed bovine ruminal microorganisms in the presence of methanogen inhibitors

Foodborne pathogen Campylobacter jejuni has been associated with ruminants. The objectives of this experiment were to determine C. jejuni survivability in mixed in vitro rumen microbial populations and the impact on methane production with or without methane inhibitors 2-bromosulfonate (BES) and/or sodium nitrate. When inoculated into rumen microbial populations without or with 0.5 mM BES, 5.0 mM nitrate or their combination, C. jejuni viability decreased from 4.7 ± 0.1 log10 colony forming units (CFU)/mL after 24 h. Loss of C. jejuni viability was greater (P < 0.05) when incubated under 100% CO2 compared to 50% H2:50% CO2, decreasing 1.46 versus 1.15 log units, respectively. C. jejuni viability was also decreased (P < 0.05) by more than 0.43 log units by the anti-methanogen treatments. Rumen microbial populations produced less methane (P = 0.05) when incubated with than without C. jejuni regardless of whether under 100% CO2 or 50% H2:50% CO2. For either gas phase, nitrate was decreased (13.2 versus 37.9%) by the anti-methanogen treatments versus controls although not always significant. C. jejuni-inoculated populations metabolized 16.4% more (P < 0.05) nitrate under H2:CO2 versus 100% CO2. Apparently, C. jejuni can compete for H2 with methanogens but has limited survivability under rumen conditions.

Effect of Chitosan on Ruminal Fermentation and Microbial Communities, Methane Emissions, and Productive Performance of Dairy Cattle.

This study aimed to expand the knowledge about the activity and mode of action of CHI on methanogenesis and rumen microbial populations in vivo. A total of 16 lactating dairy cows were distributed in two groups, one of them receiving 135 mg CHI/kg body weight daily. The effect on productive performance, milk composition, fermentation efficiency, methane emissions, microbial protein synthesis, and ruminal microbial communities was determined. Supplementation with CHI did not affect rumen microbial diversity but increased the relative abundance (RA) of the bacteria Anaeroplasma and decreased those of rumen ciliates and protozoa resulting in a shift towards a lower acetic to propionic ratio. However, no effect on milk yield or methane intensity was observed. In conclusion, supplementing 135 mg CHI/kg body weight increased the RA of Anaeroplasma and decreased those of rumen ciliates and protozoa, both being related to fiber degradation in the rumen in different ways and resulted in a shift of ruminal fermentation towards more propionate proportions, without affecting CH4 emissions, milk yield, or milk composition. Further research with higher doses would be necessary to assess the potential use of this additive as a methane inhibitor.

Silibinin reduces in vitro methane production by regulating the rumen microbiome and metabolites.

This study used Silibinin as an additive to conduct fermentation experiments, wherein its effects on rumen gas production, fermentation, metabolites, and microbiome were analyzed in vitro. The silibinin inclusion level were 0 g/L (control group), 0.075 g/L, 0.15 g/L, 0.30 g/L, and 0.60 g/L (experimental group). Fermentation parameters, total gas production, carbon dioxide (CO2), methane (CH4), hydrogen (H2), and their percentages were determined. Further analysis of the rumen microbiome's relative abundance and α/β diversity was performed on the Illumina NovaSeq sequencing platform. Qualitative and quantitative metabolomics analyses were performed to analyze the differential metabolites and metabolic pathways based on non-targeted metabolomics. The result indicated that with an increasing dose of silibinin, there was a linear reduction in total gas production, CO2, CH4, H2 and their respective percentages, and the acetic acid to propionic acid ratio. Concurrent with a linear increase in pH, when silibinin was added at 0.15 g/L and above, the total volatile fatty acid concentration decreased, the acetic acid molar ratio decreased, the propionic acid molar ratio increased, and dry matter digestibility decreased. At the same time, the relative abundance of Prevotella, Isotricha, Ophryoscolex, unclassified_Rotifera, Methanosphaera, Orpinomyces, and Neocallimastix in the rumen decreased after adding 0.60 g/L of silibinin. Simultaneously, the relative abundance of Succiniclasticum, NK4A214_group, Candidatus_Saccharimonas, and unclassified_Lachnospiraceae increased, altering the rumen species composition, community, and structure. Furthermore, it upregulated the ruminal metabolites, such as 2-Phenylacetamide, Phlorizin, Dalspinin, N6-(1,2-Dicarboxyethyl)-AMP, 5,6,7,8-Tetrahydromethanopterin, Flavin mononucleotide adenine dinucleotide reduced form (FMNH), Pyridoxine 5'-phosphate, Silibinin, and Beta-D-Fructose 6-phosphate, affecting phenylalanine metabolism, flavonoid biosynthesis, and folate biosynthesis pathways. In summary, adding silibinin can alter the rumen fermentation parameters and mitigate enteric methane production by regulating rumen microbiota and metabolites, which is important for developing novel rumen methane inhibitors.

Effect of fumaric acid in combination with Asparagopsis taxiformis or nitrate on in vitro gas production, pH, and redox potential

Reduction in enteric methane (CH4) emissions from cattle can be achieved through use of feed additives, which often results in increased emission of hydrogen (H2). The objective of this study was to investigate in vitro effects of a known hydrogen sink, fumaric acid, in combination with either of 2 methane inhibitors, the macroalga Asparagopsis taxiformis or nitrate, on CH4 and H2 production, feed degradability, pH, and redox potential. A corn silage (0.5 g; control) was incubated in buffered rumen fluid with the addition of 0.025 g of nitrate (Nit), 0.025 g of dried A. taxiformis (Asp), 0.025 g of nitrate + 0.025 g of fumaric acid (Nit+Fum), or 0.025 g of dried A. taxiformis + 0.025 g of fumaric acid (Asp+Fum). Accumulated gas production was determined using the AnkomRF system equipped with airtight gasbags. There were 9 replicates per treatment with 3 replicates per treatment stopped after 24, 36, and 48 h of incubation. The amount of undegraded feed was determined by filtration. Gas composition was determined by gas chromatography. Degradable dry matter, degradable organic matter, pH, redox potential, and gas production data were analyzed using a mixed model. Asp and Asp+Fum reduced CH4 production by 98% or greater at all incubation times, whereas Nit and Nit+Fum reduced CH4 production (mL of CH4/g of dry matter) by 52% to 63% compared with the control. Hydrogen was only detectable in gas from Asp and Asp+Fum treatments, with no difference in H2 production between the 2 treatments. The treatments had only minor effects on redox potential in the fermented rumen fluid, and pH was lowest for treatments including A. taxiformis. In conclusion, both A. taxiformis and nitrate reduced CH4 production. Fumaric acid in combination with A. taxiformis did not reduce H2 production, and treatments including nitrate did not result in any detectable levels of H2. Future dose-response in vitro studies will contribute to investigating the potential of fumaric acid as a hydrogen sink during CH4 mitigation.

Evaluation of the red seaweed Mazzaella japonica as a feed additive for beef cattle

Supplementing ruminant diets with macroalgae is gaining interest globally because bromoform-containing seaweeds (e.g., Asparagopsis spp.) have been shown to be highly effective enteric methane (CH4) inhibitors. Some alternative seaweeds decrease in vitro CH4 production, but few have been evaluated in animals. This study examined the effects of including the red seaweed Mazzaella japonica in the diet of beef cattle on dry matter intake (DMI), rumen fermentation, digestibility, nitrogen (N) utilization, and enteric CH4 production. Six ruminally cannulated, mature beef heifers (824 ± 47.1 kg) were used in a double 3 × 3 Latin square with 35-d periods. The basal diet consisted of 52% barley silage, 44% barley straw, and 4% vitamin and mineral supplement [dry matter (DM) basis]. The treatments were (DM basis): 0% (control), 1%, and 2% M. japonica. The DMI increased quadratically (P = 0.025) with the inclusion of M. japonica, such that the DMI of heifers consuming 1% was greater (P &amp;lt; 0.05) than that of control heifers. The apparent total-tract digestibility of DM decreased linearly (P = 0.002) with the inclusion of M. japonica, but there were no treatment differences in the digestibility of organic matter, crude protein (CP), neutral detergent fiber, or starch. The level of M. japonica linearly (P &amp;lt; 0.001) increased the N intake of the heifers. Fecal N excretion linearly increased (P = 0.020) with M. japonica, but there were no differences in total urinary N excretion, N fractions (allantoin, uric acid), total purine derivatives, microbial purine derivatives absorbed, microbial N flow, or retained N. There were no treatment effects on rumen pH or total volatile fatty acids (VFAs); however, adding M. japonica to the diet quadratically (P = 0.023) decreased the proportion of acetate, whereas 1% inclusion decreased the acetate proportion. Methane production (g/day) decreased quadratically (P = 0.037), such that the heifers receiving 2% M. japonica produced 9.2% less CH4 than control animals; however, CH4 yield (g/kg DMI) did not differ among treatments. We conclude that supplementing a forage-based diet with up to 2% M. japonica failed to lower the enteric CH4 yield of beef heifers. M. japonica can be used in diets to help meet the CP requirements of cattle, but inclusion rates may be limited by high inorganic matter proportions. When comprising up to 2% of the diet, M. japonica cannot be recommended as a CH4 inhibitor for beef cattle fed on high-forage diets.

Oral administration of Pinus koraiensis cone essential oil reduces rumen methane emission by altering the rumen microbial composition and functions in Korean native goat (Capra hircus coreanae).

This study aimed to investigate Pinus koraiensis cone essential oil (PEO) as a methane (CH4) inhibitor and determine its impact on the taxonomic and functional characteristics of the rumen microbiota in goats. A total of 10 growing Korean native goats (Capra hircus coreanae, 29.9 ± 1.58 kg, male) were assigned to different dietary treatments: control (CON; basal diet without additive) and PEO (basal diet +1 g/d of PEO) by a 2 × 2 crossover design. Methane measurements were conducted every 4 consecutive days for 17-20 days using a laser CH4 detector. Samples of rumen fluid and feces were collected during each experimental period to evaluate the biological effects and dry matter (DM) digestibility after PEO oral administration. The rumen microbiota was analyzed via 16S rRNA gene amplicon sequencing. The PEO oral administration resulted in reduced CH4 emission (eructation CH4/body weight0.75, p = 0.079) without affecting DM intake; however, it lowered the total volatile fatty acids (p = 0.041), molar proportion of propionate (p = 0.075), and ammonia nitrogen (p = 0.087) in the rumen. Blood metabolites (i.e., albumin, alanine transaminase/serum glutamic pyruvate transaminase, creatinine, and triglyceride) were significantly affected (p < 0.05) by PEO oral administration. The absolute fungal abundance (p = 0.009) was reduced by PEO oral administration, whereas ciliate protozoa, total bacteria, and methanogen abundance were not affected. The composition of rumen prokaryotic microbiota was altered by PEO oral administration with lower evenness (p = 0.054) observed for the PEO group than the CON group. Moreover, PICRUSt2 analysis revealed that the metabolic pathways of prokaryotic bacteria, such as pyruvate metabolism, were enriched in the PEO group. We also identified the Rikenellaceae RC9 gut group as the taxa potentially contributing to the enriched KEGG modules for histidine biosynthesis and pyruvate oxidation in the rumen of the PEO group using the FishTaco analysis. The entire co-occurrence networks showed that more nodes and edges were detected in the PEO group. Overall, these findings provide an understanding of how PEO oral administration affects CH4 emission and rumen prokaryotic microbiota composition and function. This study may help develop potential manipulation strategies to find new essential oils to mitigate enteric CH4 emissions from ruminants.

Evaluation of Rumen Methane Emission in Sahiwal and Gir Calves Supplemented with Combination of Methanogenic Inhibitors

Methane is one of the main greenhouse gases emitted by ruminants around the world. It is essential to investigate novel approaches to increasing animal production while reducing greenhouse gas emissions from ruminants. This study was conducted to examine the effect of methane inhibitors, such as nitrate, linseed oil, and anthraquinone, on nutritional digestibility, rumen fermentation processes, and methane emission in Sahiwal and Gir cattle calves. Twelve calves (6–12 months old), six of each Sahiwal and Gir breed, were selected and divided into four groups; Sahiwal control (C) and treated (T) calves; Gir control (C) and treated calves (T) of three calves each based on average body weight. Switch over a design was used as for periods 1 and 2. Animals in all groups were fed chopped oat fodder, wheat straw, and a concentrate mixture. Additionally, treated groups were fed a ration with potassium nitrate (1%), linseed oil (0.5%), and anthraquinone (4 ppm). The results revealed that the addition of methane inhibitors had no impact on nutrient intake and apparent digestibility. The levels of propionate, ammonia nitrogen, and total nitrogen were increased significantly (p &lt; 0.05), while butyrate decreased in the treated groups of both breeds. However, there was no change in acetate and pH between the groups. Methane emission (g/d) was lower (p &lt; 0.05) in the treated groups as compared to the control group. This study concludes that supplementation of methane inhibitors in calves feed can be utilized to lower methane emissions without affecting the intake and digestibility of nutrients. Combining diverse dietary mitigation strategies could be an effective way to mitigate methane emissions to reduce global warming while minimizing any negative impacts on ruminants to accomplish sustainable animal production.

Carbon, cash, cattle and the climate crisis

While society increasingly demands emissions abatement from the livestock sector, farmers are concurrently being forced to adapt to an existential climate crisis. Here, we examine how stacking together multiple systems adaptations impacts on the productivity, profitability and greenhouse gas (GHG) emissions of livestock production systems under future climates underpinned by more frequent extreme weather events. Without adaptation, we reveal that soil carbon sequestration (SCS) in 2050 declined by 45–133%, heralding dire ramifications for CO2 removal aspirations associated with SCS in nationally determined contributions. Across adaptation-mitigation bundles examined, mitigation afforded by SCS from deep-rooted legumes was lowest, followed by mitigation from status quo SCS and woody vegetation, and with the greatest mitigation afforded by adoption of enteric methane inhibitor vaccines. Our results (1) underline a compelling need for innovative, disruptive technologies that dissect the strong, positive coupling between productivity and GHG emissions, (2) enable maintenance or additional sequestration of carbon in vegetation and soils under the hotter and drier conditions expected in future, and (3) illustrate the importance of holistically assessing systems to account for pollution swapping, where mitigation of one type of GHG (e.g., enteric methane) can result in increased emissions of another (e.g., CO2). We conclude that transdisciplinary participatory modelling with stakeholders and appropriate bundling of multiple complementary adaptation-mitigation options can simultaneously benefit production, profit, net emissions and emissions intensity.

Comparative analysis of macroalgae supplementation on the rumen microbial community: Asparagopsis taxiformis inhibits major ruminal methanogenic, fibrolytic, and volatile fatty acid-producing microbes in vitro.

Seaweeds have received a great deal of attention recently for their potential as methane-suppressing feed additives in ruminants. To date, Asparagopsis taxiformis has proven a potent enteric methane inhibitor, but it is a priority to identify local seaweed varieties that hold similar properties. It is essential that any methane inhibitor does not compromise the function of the rumen microbiome. In this study, we conducted an in vitro experiment using the RUSITEC system to evaluate the impact of three red seaweeds, A. taxiformis, Palmaria mollis, and Mazzaella japonica, on rumen prokaryotic communities. 16S rRNA sequencing showed that A. taxiformis had a profound effect on the microbiome, particularly on methanogens. Weighted Unifrac distances showed significant separation of A. taxiformis samples from the control and other seaweeds (p < 0.05). Neither P. mollis nor M. japonica had a substantial effect on the microbiome (p > 0.05). A. taxiformis reduced the abundance of all major archaeal species (p < 0.05), leading to an almost total disappearance of the methanogens. Prominent fiber-degrading and volatile fatty acid (VFA)-producing bacteria including Fibrobacter and Ruminococcus were also inhibited by A. taxiformis (p < 0.05), as were other genera involved in propionate production. The relative abundance of several other bacteria including Prevotella, Bifidobacterium, Succinivibrio, Ruminobacter, and unclassified Lachnospiraceae were increased by A. taxiformis suggesting that the rumen microbiome adapted to an initial perturbation. Our study provides baseline knowledge of microbial dynamics in response to seaweed feeding over an extended period and suggests that feeding A. taxiformis to cattle to reduce methane may directly, or indirectly, inhibit important fiber-degrading and VFA-producing bacteria.