Ruminal Methane Emissions Research Articles

Effect of High-Tannin and -Polyphenol Plant Material Supplement on Rumen Fermentation, Nitrogen Partitioning and Nutrient Utilization in Beef Cattle.

The current issue of ruminant methane emissions is still being researched by animal nutritionists in an effort to find new approaches. In this study, five beef cattle were randomly assigned in a 5 × 5 Latin square design to examine the effects of supplementation with high-tannin and -polyphenol plant materials on nutrient utilization, rumen fermentation, and nitrogen partitioning. Cattle offered total mixed ration (TMR) silage diets with or without tannin-rich tree leaf or plant herbs, such as Piper sarmentosum Roxb., Cymbopogon citratus (DC.) Stapf, Anacardium occidentale L., and Careya arborea Roxb., were supplemented at a dose of 10 g/d. Prior to TMR feeding, the animals' meals were supplemented with 10 g of fortified plant materials twice a day, along with 100 g of rice bran. The animals in the control group received only 100 g of rice bran and no other plant materials. The result showed that there was no difference in nutrient intake or digestibility between the supplemented and control groups. Although the effect of ruminal pH, NH3-N, Total VFA, acetate (C2), and butyrate (C4) was not significant (p > 0.05), the proportion of propionate (C3) tended to increase with supplementation (p = 0.07). There was no difference in the excretion of purine derivatives or the amount of microbial nitrogen supply, even though supplemented animals had significantly lower protozoal populations than the control group (p < 0.05). Moreover, when A. occidentale or C. arborea was added to the TMR silage diet, the nitrogen intake and retention increased considerably, although total nitrogen excretion decreased. In this approach, the leaves of Anacardium occidentale L. and Careya arborea Roxb. were particularly promising for strategic supplementation.

Hydroponic fodder as alternative feeds for ruminants to reduce ruminal methane emissions: an in vitro study

Malate, a precursor in the ruminal propionate production pathway, competes with methanogenesis for metabolic hydrogen, offering a way to reduce ruminal methane (CH4) production in ruminants. However, cost considerations hinder widespread use of malate in ruminant diets. An alternative approach involves utilizing transient malate levels generated during seed germination via the glyoxylate cycle. This study investigated the methane-mitigating potential of malate-containing hydroponic fodder. Fodder samples with peak malate concentrations from alfalfa, forage pea, Italian ryegrass, rye, soybean, triticale, and wheat during germination were subjected to in vitro rumen fermentation using the Hohenheim gas test. The basal diet of in vitro fermentation comprised 40% grass silage, 40% maize silage, 15% hay, and 5% concentrate on a dry matter basis, with nutritional characteristics including 42.1% neutral detergent fiber (NDF), 25.0% acid detergent fiber, 14.0% starch, 12.7% crude protein, and 3.5% ether extract (EE), on a dry matter basis. Experimental treatments were fodder inclusion involved replacing 20% of the basal diet (20R), and additionally, 100% replacement of the silages with alfalfa d 10 and rye d 9 (SR), the 2 high-malate fodders. Reductions in CH4 production were observed with soybean (20R, 6.7% reduction), alfalfa (20R, 6.6% reduction), and increased with rye (20R, 6.3% increase). In the setup replacing silages with high-malate fodders (SR), alfalfa decreased CH4 production (17.7%) but increased ammonia (174%), while rye increased CH4 production (35.8%). Organic matter digestibility increased with SR rye (12.6%). Marginal effects of dietary variables were analyzed in a Generalized Additive Model. A negative relationship between dietary malate content and CH4 production was observed, whereas dietary NDF and starch content were positive correlated with CH4 production. In conclusion, malate within the hydroponic fodder could potentially reduce CH4 emissions in ruminants. However, achieving sufficient efficacy requires high malate content. Additionally, use of hydroponic fodder may increase the risk of nitrogen emissions. Animal studies are required for further investigation.

Seaweed as a feed additive to mitigate enteric methane emissions in ruminants: Opportunities and challenges1

Cutting farming-related methane emissions from ruminants is critical in the battle against climate change. Since scientists initially investigated the potential of marine macroalgae to reduce methane emissions, using seaweeds as an anti-methanogenic feed additive has become prevailing in recent years. Asparagopsis taxiformis is the preferred species because it contains a relatively higher concentration of bromoform. As a type of halogenated methane analogue, bromoform contained in A. taxiformis can specifically inhibit the activity of coenzyme M methyltransferase, thereby blocking the ruminal methanogenesis. However, bromoform is a potential toxin and ozone-depleting substance. In response, current research focuses on the effects of bromoform-enriched seaweed supplementation on ruminant productivity and safety, as well as the impact of large-scale cultivation of seaweeds on the atmospheric environment. The current research on seaweed still needs to be improved, especially in developing more species with low bromoform content, such as Bonnemaisonia hamifera, Dictyota bartayresii, and Cystoseira trinodis. Otherwise, seaweed is rich in bioactive substances and exhibits antibacterial, anti-inflammatory, and other physiological properties, but research on the role of these bioactive compounds in methane emissions is lacking. It is worthy of deeper investigation to identify more potential bioactive compounds. As a new focus of attention, seaweed has attracted the interest of many scientists. Nevertheless, seaweed still faces some challenges as a feed additive to ruminants, such as the residues of heavy metals (iodine and bromine) and bromoform in milk or meat, as well as the establishment of a supply chain for seaweed cultivation, preservation, and processing. We have concluded that the methane-reducing efficacy of seaweed is indisputable. However, its application as a commercial feed additive is still influenced by factors such as safety, costs, policy incentives, and regulations.

Exploring the combination of Asparagopsis taxiformis and phloroglucinol to decrease rumen methanogenesis and redirect hydrogen production in goats

Many strategies for mitigating enteric methane (CH4) emissions in ruminants have focused on suppressing the activity of rumen methanogens, but this often leads to excess dihydrogen (H2) accumulation in the rumen, which is subsequently expelled and represents a potential energy loss. We hypothesized that phloroglucinol could act as a H2 acceptor when rumen methanogenesis is inhibited and be potentially transformed into beneficial compounds for the animal. Eight adult goats were randomly assigned to a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments: two levels of Asparagopsis taxiformis as CH4 inhibitor [0 vs. 5 g/kg on a dry matter (DM) basis; AT- and AT+, respectively] and two levels of phloroglucinol as alternative H2 acceptor (0 vs. 20 g/kg DM, PG- and PG+, respectively). Therefore, four dietary treatments were considered: i) basal diet (AT-PG-); ii) A. taxiformis alone (AT+PG-); iii) phloroglucinol alone (AT-PG+); and iv) the combination of A. taxiformis and phloroglucinol (AT+PG+). Animals were fed a maintenance diet with a 70:30 forage-to-concentrate ratio. After 10 d of adaptation to the diet, enteric gas emissions were measured in respiration chambers during 3 d prior to rumen content sampling on d 14. Dietary supplementation with A. taxiformis decreased CH4 production (-33.9 %) and increased H2 emissions (+3465 %), along with greater rumen propionate concentration. In contrast, phloroglucinol supplementation alone did not impact CH4 emissions or the rumen concentration of the main microbial groups but substantially increased acetate molar proportion (+10.2 %) which could act as an alternative H2 acceptor. Moreover, when A. taxiformis was combined with phloroglucinol, it resulted in a decrease in H2 emissions (-68.1 %). However, this decrease in H2 emissions was not fully explained by the increase in the acetate as phloroglucinol led to an increase in acetate both when methanogenesis was inhibited and when it was not. These findings suggest that the rumen fermentation of phloroglucinol may capture some of the additional H2 arising from the inhibition of methanogenesis by A. taxiformis through pathways other than acetate formation. Moreover, H2 emissions were not eliminated and most of the decrease occurred during the post-prandial stage, suggesting that the efficiency of H2 redirection could be further improved.

Methane gas production and phenolic compound of two species in tropical brown seaweeds

Abstract A study has indicated that the metabolites found in seaweed can lower methane emissions from ruminants, especially the phenolic compound. Indonesia is a tropical nation where seaweed variety is abundant, but it has not been widely reported to be used to reduce ruminant methane emissions. The research aims to measure the methane gas production and phenolic compound of two species in tropical brown seaweeds (Laminaria Sp. and Padina australis) from Tuban, East Java, in Kelapa Beach, Indonesia. The treatments were completely randomized with four replications and t test for the differences among treatment means. After a 24-hour incubation period, 10 mL samples used for the analysis of methane gas production were taken from the aliquot, preserved in a vacuum tube, and measured using gas chromatography (GC). The phenolic compound analysis included phenol, tannin, and flavonoid with a spectrophotometer according to Makkar (2003) and Arvouet-Grand et al. (1994) method. The result showed that Padina australis (2.47 mL and 13.00 mL/g DM) is lower in methane than Laminaria sp. (3.41 mL and 18.41 mL/g DM). Meanwhile, Padina australis is higher in flavonoid, phenol, and tannin (3.99, 0.88, 0.87 mg/g DM respectively) than Laminaria sp. (2.73, 0.63, 0.61 mg/g DM respectively). It was concluded that from two species of tropical brown seaweed, Padina australis had more potential to reduce methane emission than Laminaria sp. due to higher phenolic compounds (flavonoid, phenol, and tannin).

A meta-analysis of probiotic interventions to mitigate ruminal methane emissions in cattle: implications for sustainable livestock farming

In recent years, the significant impact of ruminants on methane emissions has garnered international attention. While dietary strategies have been implemented to solve this issue, probiotics gained the attention of researchers due to their sustainability. However, it is challenging to ascertain their effectiveness as an extensive range of strains and doses have been reported in the literature. Hence, the objective of this experiment was to perform a meta-analysis of probiotic interventions aiming to reduce ruminal methane emissions from cattle. From 362 articles retrieved from scientific databases, 85 articles were assessed independently by two reviewers, and 20 articles representing 49 comparisons were found eligible for meta-analysis. In each study, data such as mean, SD, and sample sizes of both the control and probiotic intervention groups were extracted. The outcomes of interest were methane emission, methane yield, and methane intensity. For the meta-analysis, effect sizes were pooled using a fixed effect or a random effect model depending on the heterogeneity. Afterward, sensitivity analyses were conducted to confirm the robustness of the findings. Overall pooled standardized mean differences (SMDs) with their confidence intervals (CIs) did not detect significant differences in methane emission (SMD = −0.04; 95% CI = −0.18–0.11; P = 0.632), methane yield (SMD = −0.08; 95% CI = −0.24–0.07; P = 0.291), and methane intensity (SMD = −0.22; 95% CI = −0.50–0.07; P = 0.129) between cattle supplemented with probiotics and the control group. However, subgroup analyses revealed that multiple-strain bacterial probiotics (SMD = −0.36; 95% CI = −0.62 to −0.11; P = 0.005), specifically the combination of bacteria involved in reductive acetogenesis and propionate production (SMD = −0.71; 95% CI = −1.04 to −0.36; P = 0.001), emerged as better interventions. Likewise, crossbreeds (SMD = −0.48; 95% CI = −0.78 to −0.18; P = 0.001) exhibited a more favorable response to the treatments. Furthermore, meta-regression demonstrated that longer periods of supplementation led to significant reductions in methane emissions (P = 0.001), yield (P = 0.032), and intensity (P = 0.012) effect sizes. Overall, the results of the current study suggest that cattle responses to probiotic interventions are highly dependent on the probiotic category. Therefore, extended trials performed with probiotics containing multiple bacterial strains are showing the most promising results. Ideally, further trials focusing on the use of probiotics to reduce ruminal methane in cattle should be conducted to complete the available literature.

Methane production from locally available ruminant feedstuffs in Ethiopia – An in vitro study

Achieving optimal nutrient composition in locally sourced ruminant feeds is important, but can be challenging in resource-limited production systems. For example, improving the composition of available local feed resources is a key obstacle to efficiently mitigating enteric methane (CH4) emissions in ruminants. This study characterized the nutritional content and in vitro methane (CH4) yield of ruminant feedstuffs accessible in Ethiopia. A survey of 60 experienced farmers in two representative districts in Amhara region, Ethiopia, provided 33 feed samples, which were classified into four ruminant feed categories: Grasses (n=10); indigenous plants (trees, shrubs, herbaceous plants) (n=13); crop residues (n=5); and agro-industrial by-products (n=5). Nutritional composition was assessed by proximate and detergent methods. Methane yield (g CH4/kg feed dry matter (DM)) and total gas yield (L/kg DM) were evaluated using a fully automated in vitro gas production system. A colorimetric assay was conducted to measure condensed tannin content (CT, mg/g) in relevant feeds. Lower crude protein (CP) values were observed for the grass (mean 65.2 g/kg DM) and crop residues (mean 54.5 g/kg DM) categories. Agro-industrial by-products had the highest CP (mean 260 g/kg DM), while indigenous plants exhibited intermediate levels (163 g/kg DM). There was significant variation in CH4 yield (P<0.01) between grasses (12.4–24.7 g/kg DM) indigenous plants (1.8–19.3 g/kg DM), and agro-industrial by-products (8.1–26.9 g/kg DM). The indigenous plant Trifolium acaule gave the lowest in vitro CH4 yield (1.8 g/kg DM). A positive relationship was observed between in vitro dry matter digestibility (IVDMD), CH4, and total gas yield. Percentage of CH4 in total gas production varied with feed category (grasses 14.5–19.6%; indigenous plants 3.1–16.9%; crop residues 15.8–20.6%; agro-industrial by-products 12.8–18.7%), and within category, e.g., Trifolium acaule (3.1%), Acacia nilotica L. (7.1%), Ziziphus spina-christi (9.9%), brewer’s spent grains (BSG) (12.8%), local liquor (areki) residues (14.1%), and local beer (tella) residues (15.1%). A negative relationship was observed between CT content and in vitro CH4 yield, with a stronger (P<0.05) correlation for soluble CTs (R2 = 0.46) than cell-bound CTs (R2 = 0.25) and total CTs (R2 = 0.29). Based on methanogenic properties and effects of CTs on in vitro CH4 yield, indigenous plants should be prioritized in ruminant rations in Ethiopia. Making nutritional composition and CH4 data publicly available could help develop environmentally sound, cost-effective rations for ruminant livestock, benefiting local farmers and leading to more sustainable and efficient livestock production in Ethiopia.

Ruminal methane emission and lactational performance of cows fed rapeseed cake and oats on a grass silage–based diet

The objective of this experiment was to investigate the effect of lipid from rapeseed cake and oats on ruminal CH4 emission and lactational performance of dairy cows. Twelve lactating Nordic Red cows, of which 4 were primiparous, and averaging (±SD) 48 ± 22.9 DIM, 37.8 ± 7.14 kg/d milk yield were enrolled in a switch-back design experiment with 3 periods of 4 wk each. The cows were assigned into 6 pairs based on parity, DIM, milk yield, and BW at the beginning of the experiment. The experimental treatments were (1) rapeseed cake and oats (RSC+O), and (2) rapeseed meal and barley (RSM+B) as the concentrate feeds. Cows in each pair were randomly assigned to 1 of the 2 groups, which received the treatments in 2 different sequences (i.e., group 1 received RSC+O in period 1 and 3, and RSM+B in period 2, whereas group 2 was fed RSM+B in period 1 and 3, and RSC+O in period 2). The diets consisted of a partially mixed ration with grass silage mixed with either oats or barley, according to the treatment sequence, and the rapeseed cake or meal being mixed into a pellet with either oats or barley according to the treatments, and a mineral mix. The pellet was delivered at a fixed amount (i.e., 6 kg/d for multiparous and 5 kg/d for the primiparous cows) from the milking robot. The actual forage to concentrate ratios for RSC+O and RSM+B were 51:49 and 52:48, respectively, with NDF concentrations of 41.5% and 36.0% and CP concentrations of 17.0% and 16.7% of diet DM. Dry matter intake, milk yield, and gas exchange (with a GreenFeed system attached to the milking robot) were recorded daily, and milk composition and spot fecal samples were collected during the last week of each period. Based on feed analysis, and DMI of the cows during the experiment, the total fat content of the experimental diets was 4.1% and 2.7% of DM for RSC+O and RSM+B diets, respectively. Dry matter intake was 1.6 kg/d lower, and milk yield tended to be 1.0 kg/d greater for RSC+O versus RSM+B. There were no differences in ECM yield and milk composition between the treatments, whereas milk ME efficiency was greater for cows fed RSC+O than RSM+B. Methane yield (g/kg DMI) did not differ between treatments, but CH4 production (g/d) was 9.4% and CH4 intensity as g/kg ECM was 11.7% lower for RSC+O versus RSM+B. The lower CH4 production was likely caused by the lower DMI and fiber digestibility, observed with the RSC+O diet. In addition, the greater lipid intake also contributed to lower rate of fermentation and subsequent decrease in CH4 production. Overall, feeding rapeseed cake with oats in a grass silage-based diet increased feed efficiency while decreasing CH4 emission intensity in lactating cows. This provides a practical way of mitigating ruminal CH4 emission from dairy operations while maintaining milk production with commonly used feedstuffs in Nordic conditions.

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.

Alternative Approaches to Feeding Small Ruminants and Their Potential Benefits.

Small ruminants, such as sheep (Ovisaries) and goats (Capra hircus), contribute to approximately 475 million metric tons of carbon dioxide equivalent (MtCO2e) greenhouse gas (GHG) emissions, accounting for approximately 6.5% of the global emissions in the agriculture sector. Crop residues, silage, grasses, hay, browse, plant leaves, shrubs, agro-industrial by-products, poultry litter, and other alternative feed sources are frequently utilized for small ruminant production. The use of these valuable alternative feeds can significantly improve animal productivity and reduce carbon footprints and GHG fluxes, making it both environmentally friendly and cost-effective. Additionally, these alternative feeds possess antioxidant, antimicrobial, and antiseptic properties that can enhance the quality of the meat and milk produced. By impacting the bacteria involved in ruminal biohydrogenation, alternative feeds can reduce methane emissions and contribute to a decrease in the carbon footprint. Overall, the use of alternative feed sources for small ruminants generally improves their apparent nutrient digestibility and productivity, and has an impact on the production of greenhouse gases, especially methane. Finally, this review recommends evaluating the economic analysis of reducing methane emissions in small ruminants by utilizing different feed sources and feeding techniques.

Determining Appropriate Numbers and Times of Daily Measurements Using GreenFeed System to Estimate Ruminal Methane Emission of Meat Goats.

The study was conducted to determine appropriate numbers and times of daily gas measurements to estimate total daily methane (CH4) emission of meat goats using a GreenFeed system (GFS). A replicated 4 (four measurement protocols) × 4 (four periods) Latin square design was employed with 16 Boer wethers in a confinement pen setting. Measurement protocols entailed three (G-3T; 0600-0700, 1400-1500, and 2200-2300 h), four (G-4T; 0700-0800, 1300-1400, 1900-2000, and 0100-0200 h), and six (G-6T; 0800-0900, 1200-1300, 1600-1700, 2000-2100, 0000-0100, and 0400-0500 h) times for daily measurement periods in GFS. The fourth protocol was continuous measurement over 24 h with animals in an open-circuit respiration calorimetry system (CS). Oat hay was given in individual feeders, and a small predetermined quantity of a pelleted concentrate supplement (bait) was dispensed by the GFS or manually offered for the CS. Overall, total dry matter (DM) intake (614, 625, 635, and 577 g/day for CS, G-3T, G-4T, and G-6T, respectively; SEM = 13.9) and digestible DM intake (359, 368, 374, and 320 CS, G-3T, G-4T, and G-6T, respectively; SEM = 15.9) were lower for CS than for G-3T, G-4T, and G-6T (p < 0.05), but these variables were not different among the GFS protocols. There was a significant (p < 0.001) effect of measurement protocol on CH4 emission in g/day (11.1, 25.6, 27.3, and 26.7 for CS, G-3T, G-4T, and G-6T, respectively; SEM = 1.11), g/kg DM intake (19.3, 46.4, 43.9, and 42.4 for CS, G-3T, G-4T, and G-6T, respectively; SEM = 2.03), and g/kg body weight (0.49, 1.11, 1.18, and 1.16 for CS, G-3T, G-4T, and G-6T, respectively; SEM = 0.052), with values being much lower for CS than for G-3T, G-4T and G-6T. Conversely, CH4 emission was similar among the GFS protocols despite differences in the time and number of daily visits (2.03, 2.76, and 3.75 visits for G-3T, G-4T, and G-6T, respectively; SEM = 0.114; p < 0.001). Pearson correlation (r) analysis indicated a moderate to high (p < 0.05) correlation between CS and G-3T (r = 0.62 for CH4 in g/day and r = 0.59 for CH4 in g/kg BW), CS and G-4T (r = 0.67 for CH4 in g/day and r = 0.76 for CH4 in g/kg BW), and CS and G-6T (r = 0.70 for CH4 in g/day and r = 0.75 for CH4 in g/kg BW). However, the correlation coefficient for CH4 in g/kg DM intake was low between CS and G-3T (r = 0.11) and CS and G-6T (r = 0.31) but slightly greater between CS and G-4T (r = 0.47). In conclusion, the results suggest that CH4 emissions using GFS in a confinement setting were greater compared with the CS in goats, but CH4-emission estimation using the GFS correlated with the CH4 emission in the CS system with a stronger relationship for the four times of daily measurements.

Accuracy validation of open-circuit respiration chambers for the assessment of energy metabolism and enteric methane emissions in pigs and small ruminants

Respiratory chambers are one of the main methods of obtaining data regarding animal energy metabolism and determine enteric methane emissions from livestock. The boom in research examining methane emissions has led to an increase in the number of facilities where such measurements can be performed. This has concerned various research groups, and emphasis has been placed on implementing a method for validating respiratory chambers according to international standards, thus ensuring that the results are traceable. This study aimed to validate the accuracy of two respiratory chambers for assessing animal energy metabolism and enteric methane emissions from livestock using international standards. The analyzers (oxygen, carbon dioxide, and methane), duct and air extraction system, and chamber were the three components used to validate the complete respiratory chamber system. The linearity and response time of the analyzers, stability of the plateau, and recovery of high-purity gases from the chambers were evaluated for the three components. The average variations in the gas measurements for the supplied reference gas were 1.77 and 1.30 % for the carbon dioxide and methane analyzers, respectively. Recovery test calculations after supplying high-purity carbon dioxide and methane into chambers revealed that the efficiency of gas recovery averages were 1.018 ± 0.0001 and 0.991 ± 0.0001 for chambers one and two, respectively. In conclusion, the respiratory chambers at the National Center of Disciplinary Research in Animal Physiology of INIFAP, Mexico designed for evaluating energy metabolism and enteric methane emissions in livestock, work with accuracy.

Unraveling the phylogenomic diversity of Methanomassiliicoccales and implications for mitigating ruminant methane emissions

BackgroundMethanomassiliicoccales are a recently identified order of methanogens that are diverse across global environments particularly the gastrointestinal tracts of animals; however, their metabolic capacities are defined via a limited number of cultured strains.ResultsHere, we profile and analyze 243 Methanomassiliicoccales genomes assembled from cultured representatives and uncultured metagenomes recovered from various biomes, including the gastrointestinal tracts of different animal species. Our analyses reveal the presence of numerous undefined genera and genetic variability in metabolic capabilities within Methanomassiliicoccales lineages, which is essential for adaptation to their ecological niches. In particular, gastrointestinal tract Methanomassiliicoccales demonstrate the presence of co-diversified members with their hosts over evolutionary timescales and likely originated in the natural environment. We highlight the presence of diverse clades of vitamin transporter BtuC proteins that distinguish Methanomassiliicoccales from other archaeal orders and likely provide a competitive advantage in efficiently handling B12. Furthermore, genome-centric metatranscriptomic analysis of ruminants with varying methane yields reveal elevated expression of select Methanomassiliicoccales genera in low methane animals and suggest that B12 exchanges could enable them to occupy ecological niches that possibly alter the direction of H2 utilization.ConclusionsWe provide a comprehensive and updated account of divergent Methanomassiliicoccales lineages, drawing from numerous uncultured genomes obtained from various habitats. We also highlight their unique metabolic capabilities involving B12, which could serve as promising targets for mitigating ruminant methane emissions by altering H2 flow.

Condensed tannins fed to dairy goats: Effects on digestibility, milk production, blood parameters, methane emission, and energy and nitrogen balances

Condensed tannins (CT) are plant polyphenols that can affect feed digestibility and are potentially able to reduce enteric CH4 emissions in ruminants. In this in vivo trial with 8 lactating goats, we investigated the effects of 4 levels of inclusion of a commercial CT extract from quebracho (0%, 2%, 4%, and 6% on dry matter basis; CON, Q2, Q4, and Q6, respectively). The experimental design was a repeated 4 × 4 Latin square with 28-d periods (24 d of diet adaptation and 4 d of sample collection) using metabolic cages and 4 open-circuit respiration chambers. The inclusion of CT in the diets did not affect the dry matter intake (DMI) but caused a linear decrease in diet digestibility, with reductions up to -11% for dry matter, -21% for crude protein (CP), -23% for α-amylase- and sodium sulfite-treated neutral detergent fiber corrected for insoluble ash (aNDFom), and -13% for gross energy, when comparing the Q6 and CON diets. However, ruminal total volatile fatty acids (VFA) concentration was not affected by CT, although there were changes in VFA proportions. Milk yield was highest for Q4 (3,371 g/d) and lowest for Q6 (3,066 g/d). In terms of milk composition, CT induced a linear reduction of fat and CP concentrations. The reduction in CP digestibility resulted in a linear reduction in the milk urea level, up to -37% with Q6. Positively, CT linearly reduced the somatic cells count expressed as linear score. The feed efficiency was linearly decreased by CT inclusion. Furthermore, a shift from urinary to fecal nitrogen excretion was observed with CT. The retained nitrogen was always negative (on average -1.93 g/d). The CH4 yield (on average 19.2 g of CH4/kg DMI) was linearly reduced by CT inclusion, up to -18% with Q6. Regarding the CH4 intensity, CT induced a linear reduction when expressed per kilogram of milk, but not per kilogram of fat and protein-corrected milk. Moreover, the CH4 production per kilogram of digestible aNDFom was linearly increased by CT. The metabolizable energy intake (MEI) was not affected by the treatments, but the metabolizability (q = MEI/gross energy intake) was reduced as CT inclusion increased. From the results of the present study, it turned out that CT have a negative impact on feed digestibility and feed use efficiency. Condensed tannins can lower CH4 emissions from ruminants; however, the main mechanism of action is likely the decrease in feed digestibility. Furthermore, CT did not improve the N use efficiency. According to these findings, the positive environmental impacts of CT are only related to the shift from urinary to fecal N excretion.

Effect of sodium formate and lactic acid bacteria treated rye silage on methane yield and energy balance in Hanwoo steers.

This study was performed to evaluate the effects of rye silage treated with sodium formate (Na-Fa) and lactic acid bacteria (LAB) inoculants on the ruminal fermentation characteristics, methane yield and energy balance in Hanwoo steers. Forage rye was harvested in May 2019 and ensiled without additives (control) or with either a LAB inoculant or Na-Fa. The LAB (Lactobacillus plantarum) were inoculated at 1.5 × 1010 CFU/g fresh matter, and the inoculant was sprayed onto the forage rye during wrapping at a rate of 4 L/ton of fresh rye forage. Sixteen percent of the Na-Fa solution was sprayed at a rate of approximately 6.6 L/ton. Hanwoo steers (body weight 275 ± 8.4 kg (n = 3, group 1); average body weight 360 ± 32.1 kg (n = 3, group 2)) were allocated into two pens equipped with individual feeding gates and used in duplicated 3 × 3 Latin square design. The experimental diet was fed twice daily (09:00 and 18:00) during the experimental period. Each period comprised 10 days for adaptation to the pen and 9 days for measurements in a direct respiratory chamber. The body weights of the steers were measured at the beginning and at the end of the experiment. Feces and urine were collected for 5 days after 1 day of adaptation to the chamber, methane production was measured for 2 days, and ruminal fluid was collected on the final day. In the LAB group, the ratio of acetic acid in the rumen fluid was significantly lower (p = 0.044) and the ratio of propionic acid in the rumen fluid was significantly higher (p = 0.017). Methane production per DDMI of the Na-FA treatment group was lower than that of the other groups (p = 0.052), and methane production per DNDFI of the LAB treatment group was higher than that of the other groups (p = 0.056). The use of an acid-based additive in silage production has a positive effect on net energy and has the potential to reduce enteric methane emissions in ruminants.

Unveiling microbial biomarkers of ruminant methane emission through machine learning.

Enteric methane from cow burps, which results from microbial fermentation of high-fiber feed in the rumen, is a significant contributor to greenhouse gas emissions. A promising strategy to address this problem is microbiome-based precision feed, which involves identifying key microorganisms for methane production. While machine learning algorithms have shown success in associating human gut microbiome with various human diseases, there have been limited efforts to employ these algorithms to establish microbial biomarkers for methane emissions in ruminants. In this study, we aim to identify potential methane biomarkers for methane emission from ruminants by employing regression algorithms commonly used in human microbiome studies, coupled with different feature selection methods. To achieve this, we analyzed the microbiome compositions and identified possible confounding metadata variables in two large public datasets of Holstein cows. Using both the microbiome features and identified metadata variables, we trained different regressors to predict methane emission. With the optimized models, permutation tests were used to determine feature importance to find informative microbial features. Among the regression algorithms tested, random forest regression outperformed others and allowed the identification of several crucial microbial taxa for methane emission as members of the native rumen microbiome, including the genera Piromyces, Succinivibrionaceae UCG-002, and Acetobacter. Additionally, our results revealed that certain herd locations and feed composition markers, such as the lipid intake and neutral-detergent fiber intake, are also predictive features for methane emissions. We demonstrated that machine learning, particularly regression algorithms, can effectively predict cow methane emissions and identify relevant rumen microorganisms. Our findings offer valuable insights for the development of microbiome-based precision feed strategies aiming at reducing methane emissions.

Exploring strategies to mitigate methane emissions in ruminants through ‘direct-fed microbials’

Exploring strategies to mitigate methane emissions in ruminants through ‘direct-fed microbials’

PSII-1 Determining Appropriate Numbers and Times of Daily Measurements to Estimate Ruminal Methane Emission of Meat Goats Using a Greenfeed System

Abstract The study was conducted to determine appropriate numbers and times of daily measurements to estimate methane production by meat goats using a GreenFeed (GF) system. Sixteen Boer wethers with an initial age of 7.4 ± 0.08 months and BW of 20.02 ± 0.71 kg were situated in a 12.4 × 12.4 pen. Oat hay, which was the major dietary constituent, was offered twice daily in individual Calan Gate feeders. Concentrate-based pellets were used as bait feed to attract animals to visit the GF regularly. The system was programed using C-Lock Inc. software to automatically dispense a small amount of pellets (120 g/day) and to measure methane production using sensors in the system. Each animal had a unique RFID tag identified by RFID reader in the system. There were 3, 4, and 6 equally spaced 1-h feeding and measurement periods (i.e., 0600-0700, 1400-1500, and 2200-2300 h for GF-3T, 0700-0800, 1300-1400, 1900-2000, and 0100-0200 h for GF-4T, and 0800-0900, 1200-1300, 1600-1700, 2000-2100, 0000-0100, and 0400-0500 h for GF-6T, respectively). The study was a Latin square with each feeding period assigned to each animal for a 2-wk period. Data were analyzed with mixed model procedures of SAS. Methane emission in g/day and g/kg dry matter intake (DMI) were not impacted by feeding period (P &amp;gt; 0.05). When expressed in g/min, g/visit, and g·visit-1·min-1, differences in CH4 production between feeding schedule were significant (P &amp;lt; 0.02). The GF-6T treatment resulted in greatest emission of CH4 in g/min (5.7, 5.9, and 6.6 for GF-3T, GF-4T, and GF-6T, respectively; P &amp;lt; 0.04). On the other hand, CH4 emission in g/visit ranked (P &amp;lt; 0.05) GF-3T &amp;gt; GF-4T &amp;gt; GF-6T (12.8, 10.9, and 7.3, respectively). Regarding CH4 intensity (g/kg BW), the differences between treatments were not significant (1.10, 1.17, and 1.16 for GF-3T, GF-4T, and GF-6T, respectively; P = 0.24). Heat production (MJ/day), which was calculated from CH4, CO2, and O2 production, was greater (P &amp;lt; 0.05) for GF-3T (8.1) than for GF-6T (7.6), with that for GF-4T intermediate (7.6; P &amp;gt; 0.05). Animals of GF-3T, GF-4T, and GF-6T visited the GF 2.1, 2.8, and 3.8 times per day, which significantly (P &amp;lt; 0.001) differed from each other. Average visit length was similar for GF-3T and GF-4T (P &amp;gt; 0.05) and greater (P &amp;lt; 0.05) than for GF-6T (4.6, 4.6, and 4.1 min for GF-3T, GF-4T, and GF-6T, respectively). In conclusion, results of the study indicate that at least 3 daily feeding or measurement periods should occur between 0600 and 0700, 1400 and 1500, and 2200 and 2300 h to accurately estimate methane production using a GF system in a confinement setting.

Milled rapeseeds and oats decrease milk saturated fatty acids and ruminal methane emissions in dairy cows without changes in product sensory quality

Plant lipids in the diet are known to modify milk fatty acid (FA) composition and mitigate ruminal methane emissions. The objective of the present work was to examine the potential of milled rapeseeds and oats to decrease both milk saturated FAs and ruminal methane emissions in practical farm settings. In the pilot study, six Finnish Ayrshire cows were fed a control diet for 3 weeks, which was then followed by a lipid-rich test diet for 3 weeks. The experimental diets were based on grass silage supplemented with barley and rapeseed meals in the control diet and with oats and milled rapeseeds in the test diet. The lipid inclusion rate was 55 g/kg dry matter (DM). In the main study, the whole Finnish Ayrshire research herd in milk (n = 49–59) was used in a switch-back-designed study. The cows were fed a control diet for 3 weeks, then a test diet for 4 weeks, and, finally, a control diet for 3 weeks. The diets were the same as in the pilot study except for a lower lipid inclusion level of 50 g/kg DM. The test diet decreased DM intake by 15% and energy-corrected milk (ECM) yield by 13% in the pilot study. The adjustment of supplemental lipids from 55 g/kg to 50 g/kg DM was successful, as the DM intake decreased only by 4% relative to the control diet in the main study. Furthermore, the yields of milk, lactose, protein, and fat were also unaffected by dietary lipids in the main study. The milk fat composition was significantly altered in both studies. The milk fat saturated FAs were decreased by 16%–20% in the test diet, mainly due to the de novo FAs of 6- to 16-carbons (a reduction of 22%–48%). Milk fat cis-9 18:1 was increased by 63%–78% in the test diet relative to the control. Dairy products’ (milk, butter, and cheese) organoleptic quality was not compromised by the modified lipid profile. Ruminal methane and hydrogen intensities (n = 23; g or mg/kg ECM) were 20% and 39% lower, respectively, in the test diet than in the control diet. This reduction can be attributed to a lower amount of organic matter fermented in the rumen, as indicated by the lower DM intake and nutrient digestibility.

The mitigating effect of feeding lucerne hay cubes supplemented with an optimal combination of nitrate with l-cysteine on enteric methane emission in sheep

The combination of optimal nitrate and l-cysteine to safely mitigate rumen methane (CH4) emissions in ruminants was studied in an open-circuit respiration head-hood system using four rumen-fistulated Suffolk wethers in a 4 × 4 Latin square design. Four treatments were set up Control: fed on lucerne hay cubes without nitrate and l-cysteine, Nitrate: fed on lucerne hay cubes with 0.18 % NO3−-N in dry matter (DM)), N + Cys-H: fed on lucerne hay cubes supplemented with 0.18 % NO3−-N and 0.74 % l-cysteine (equivalent to half the upper limit of effective S requirement in DM), and N + Cys-Q: fed on lucerne hay cubes supplemented with 0.18 % NO3−-N and 0.37 % l-cysteine (equivalent to 1/4 of the upper limit of effective S requirement in DM). In this experiment, the ingested nitrate at a subclinical concentration/s (0.18 % in DM) increased by 11.2 % mean methemoglobin value and alleviated rumen methanogenesis by 47 %. Administration of l-cysteine set at 0.74 % and 0.37 % in DM reduced by 68 % and 58 % methemoglobin formed by nitrate alone, respectively (P < 0.05). However, daily mitigation of CH4 emissions decreased by 35 % with the addition of l-cysteine at both addition concentration/s compared with Control.The results of this study suggest that mitigation of enteric methane emissions by the combination of nitrate and l-cysteine can be achieved by feeding diets in which the nitrate content is maintained at around 0.18 % NO3−-N in DM and l-cysteine addition is adjusted to 0.37–0.74 % in DM. This method would be recommended as a safe, efficient, and practical way to mitigate enteric CH4 emissions leading to increased productivity while reducing the increased N excretion that causes N2O emissions.