Ruminal Methane Emissions Research Articles

Ruminal methane emissions, metabolic, and microbial profile of Holstein steers fed forage and concentrate, separately or as a total mixed ration.

Few studies have examined the effects of feeding total mixed ration (TMR) versus roughage and concentrate separately (SF) on ruminant methane production. Therefore, this study compared differences in methane production, ruminal characteristics, total tract digestibility of nutrients, and rumen microbiome between the two feeding methods in Holstein steers. A total six Holstein steers of initial bodyweights 540 ± 34 kg were divided into two groups and assigned to a same experimental diet with two different feeding systems (TMR or SF) in a crossover design with 21 d periods. The experimental diet contained 73% concentrate and 27% forage and were fed twice a day. The total tract digestibility of crude protein, neutral detergent fibre, and organic matter were not affected by the two different feeding systems. Steers fed TMR emitted more methane (138.5 vs. 118.2 L/d; P < 0.05) and lost more gross energy as methane energy (4.0 vs. 3.5% gross energy intake; P = 0.005) compared to those fed SF. Steers fed TMR had greater (P < 0.05) total volatile fatty acid (VFA), ammonia-N concentrations and propionate proportion of total VFA at 1.5 h, whereas lower after that compared to steers fed SF. The greater (P < 0.05) acetate: propionate ratio at 4.5 h for steers fed TMR reflected the shift of H2 sink from propionate towards acetate synthesis. The lower (P < 0.05) isobutyrate and isovalerate proportions of total VFA observed in steers fed TMR implies decrease in net consumption of H2 for microbial protein synthesis compared to SF. There were no differences in both major bacterial and archaeal diversity between TMR and SF, unlike several minor bacterial abundances. The minor groups such as Coprococcus, Succiniclasticum, Butyrivibrio, and Succinivibrio were associated with the changes in ruminal VFA profiles or methanogenesis indirectly. Overall, these results indicate that SF reduces methane emissions from ruminants and increases propionate proportion of total VFA without affecting total tract digestion compared to TMR. There were no evidences that the response differed due to different major underlying microbial population.

A small scale rumen incubation system to screen chemical libraries for potential methane inhibitors

There is currently an urgent need for effective anti-methanogen small molecule inhibitors to help control ruminant methane emissions on a global scale. No assays system has yet been reported that would enable high-throughput screening of either rumen methanogen cultures or an assay system that utilises rumen fluid. We report here the development of a high-throughput 0.2 ml rumen fluid-based 96-well screening system that incorporates a simple substrate for fermentation with a short incubation time The fermentation parameters determined are total gas, methane and hydrogen production. The system markedly enhances the number of samples that can be processed (∼1000 incubation vials per week) compared to previously published assays. The system does not try to mimic rumen fermentation but is a means of screening compounds for their potential effect against rumen methanogens. We also assessed the system using known rumen anti-methanogen inhibitory compounds, a set of anthraquinone derivatives and 3-nitrooxypropanol. The system can differentiate between specific methane inhibition and the inhibition of overall fermentation and it discriminates between molecules that act as methanogen inhibitors and those acting as electron sinks.

Effects of eucalyptus oil and anise oil supplementation on rumen fermentation characteristics, methane emission, and digestibility in sheep.

The objective of this study was to evaluate antimethanogenic activity of eucalyptus oil (EUC) and anise oil (ANI) in vitro and in vivo using sheep as a model. In vitro study was conducted using batch culture technique, each of EUC and ANI were added at 0, 50, 100, 200, or 400 mg/L of fermentation media with substrate containing 60% corn-based concentrate and 40% hay (DM basis). Total gas production (GP) linearly (P < 0.01) decreased with increasing ANI, whereas the GP was not affected with EUC addition. Supplementation of ANI and EUC linearly (P < 0.01) decreased total methane production and methane proportion in total gas. Total VFA and ammonia-nitrogen (NH3-N) concentration linearly (P < 0.01) decreased with increasing ANI supplementation. For the in vivo study, a replicated 3 × 3 Latin square design was carried out using six ruminal cannulated Du Han hybrid sheep (BW, 64.5 ± 8.56 kg) with 22 d of periods. Three treatments were control diet (consisted of 60% corn-based concentrate and 40% Chinese wildrye hay), EUC (control diet supplemented with 0.5 g EUC/d per head), and ANI (control diet supplemented with 0.5 g ANI/d per head). Each period consisted of 14 d for adaption and 8 d for sampling and data collection. Supplementation of EUC and ANI had no effects on feed intake and apparent nutrient digestibility. Ruminal NH3-N concentration was greater with EUC (P < 0.01) and ANI (P = 0.03) than control. Urinal allantoin output was less (P < 0.05) in sheep fed EUC and ANI than control animals. Methane emission was less (P = 0.03) in sheep fed ANI than sheep fed EUC, and a tendency of decrease for an eduction in this parameter was found for sheep fed with ANI (P = 0.08) compared to control. The in vitro results indicated a reduction of methane production with both EUC and ANI but in a dose-dependant manner. Supplementation of ANI tended to reduce ruminal methane production without adversely affecting rumen fermentation characteristics, nutrient intake, and digestibility, suggesting potential inhibition of ruminal methane emission in sheep supplemented with ANI.

Potential impacts of dietary Lemna gibba supplements in a simulated ruminal fermentation system and environmental biogas production

Abstract Enteric methane production from ruminants contributes to current global warming challenges faced by mankind. Supplements that improve nutritive value of diets are potential mitigating strategies that may reduce enteric methane emissions. This study was, therefore, designed to evaluate the potential of duckweed (Lemna gibba) supplement to reduce enteric methane emissions using an in vitro ruminal gas production technique. In the first of two experiments, Lemna gibba from two water bodies (LG1 and LG2), lucerne and ryegrass samples were analyzed for chemical composition and in vitro ruminal fermentation parameters. In the second experiment, the two Lemna gibba samples were each included in a basal diet at 5, 10, 15, 20 and 25% to create ten dietary treatments. The dietary treatments were also analyzed for chemical composition and in vitro ruminal fermentation characteristics as in the first experiment. Lemna gibba and lucerne fermentation resulted in similar propionate levels. The inclusion of 15% L. gibba had no effect on the ruminal fermentation patterns (volatile fatty acids, acetate:propionate ratio, acetate, propionate and butyrate) and the dry matter and organic matter degradability. These results indicate that L. gibba could be used in ruminant diets as an alternative to grains or concentrates with the added advantage of possibly reducing ruminal methane emissions. Dietary supplementation with L. gibba in ruminant diets could be an environmentally friendly strategy to reduce feed costs and ensure sustainable production.

Sources of nitrous oxide and other climate relevant gases on surface area in a dairy free stall barn with solid floor and outside slurry storage

Livestock production systems in agriculture are one of the major emitters of greenhouse gases. So far, the focus of research in the dairy farm sector was primarily on ruminal methane (CH4) emissions. Emissions of nitrous oxide (N2O) usually arise from solid manure or in deep litter free stall barns. Release of N2O occurs as a result of interactions between organic material, nitrogen and moisture. Data of N2O emissions from modern dairy barns and liquid manure management systems are rare. Thus, the goal of this research was to determine the main sources of trace gas emissions at the dairy farm level, including N2O. Areas such as the scraped surface area where dry and wet conditions alternate are interesting. Possible sources of trace gases within and outside the barn were localised by measuring trace gas concentration rates from different dairy farm areas (e.g., areas covered with urine and excrement or slurry storage system) via the closed chamber technique. The results indicate typical emission ratios of carbon dioxide (CO2), CH4 and N2O in the various areas to generate comparable equivalent values. Calculated on the basis of nitrogen excretion from dairy cows, total emissions of N2O were much lower from barns than typically measured in fields. However, there were also areas within the barn with individual events and unexpected release factors of N2O concentrations such as urine patches, polluted areas and cubicles. Emission factors of N2O ranged from 1.1 to 5.0 mg m−2 d−1, respectively, for cleaned areas and urine patches. By considering the release factors of these areas and their proportion of the entire barn, total emission rates of 371 CO2-eq. LU−1 a−1, 36 CO2-eq. LU−1 a−1, and 1.7 kg CO2-eq. LU−1 a−1 for CO2, CH4 and N2O, respectively, were measured for the whole barn surface area. The CH4 emissions from surface area were stronger climate relevant comparing to N2O emissions, but compared to CH4 emissions from slurry storage or ruminal fermentation (not measured) even insignificant.

Potential of Samanea saman pod meal for enteric methane mitigation in crossbred heifers fed low-quality tropical grass

Pods of Samanea saman have been reported to be effective in mitigating methane (CH4) emissions in ruminants. The aim of this study was to evaluate the effect of inclusion of S. saman pod meal in the ration on feed intake, apparent digestibility, rumen fermentation, rumen degradation, protozoa population, and enteric CH4 emissions in crossbred heifers fed low-quality tropical grass. Four crossbred heifers (Bos taurus × B. indicus) with an average live weight (LW) of 261.5 ± 1.29 kg were used in a 4 × 4 Latin square design with four periods of 23 days (17 days for adaptation and 6 days for measurements of response variables). Levels of inclusion of S. saman ground pods in the ration were 0, 10, 20 and 30% of dry matter (DM). Enteric CH4 emissions were measured using open-circuit respiration chambers. Additionally, rumen degradation of the different components of S. saman pods was assessed. Incorporation of S. saman levels had no effect on dry matter intake (DMI) (P > .05), apparent digestibility of dry matter (DM) and organic matter (OM) (P > .05) nor protozoal count (P > .05). It was found that molar proportion of propionic acid in rumen liquid was increased (P < .05), while that of acetic acid and acetic:propionic ratio was linearly decreased (P < .01) when heifers were supplemented with S. saman. Additionally, emissions of enteric CH4 showed a linear reduction as the inclusion of S. saman in the ration was increased (P = .007). A reduction of 50.9% in L CH4/day and 56.9% in L CH4/kg DM intake was observed at the highest inclusion level of S. saman compared to the control diet (P < .05). Potential degradation of DM of pods of S. saman was 79.6%. It is concluded that, the inclusion of S. saman pods in the ration has the capacity to reduce energy losses in the form of methane emissions in heifers fed low-quality tropical grass.

Effects of different levels of lespedeza and supplementation with monensin, coconut oil, or soybean oil on ruminal methane emission by mature Boer goat wethers after different lengths of feeding

ABSTRACTMature Boer goat wethers were supplemented with 0.5% BW rolled corn and consumed pelleted alfalfa (CON), pelleted Sericea lespedeza (HSL; 6.4% condensed tannins), a 1:1 mixture of alfalfa and lespedeza (MSL), or alfalfa with monensin (ION; 22 mg/kg), coconut oil (CCO; 4%), or soybean oil (SBO; 4%). Total DM intake in the 20-wk study (3.86%, 3.75%, 3.52%, 3.69%, and 3.64% BW) and total tract OM digestibility determined every 5 wk (72.8%, 69.5%, 70.3%, 72.0%, and 71.1%) were not affected by treatment, although there were differences in nitrogen digestion (77.5%, 70.7%, 67.0%, 77.0%, 75.7%, and 73.6% for CON, MSL, HSL, ION, CCO, and SBO, respectively; SEM = 1.76). Ruminal methane emission was not influenced by period and was lowest among treatments for CON expressed as percentages of gross (10.3%, 6.8%, 6.3%, 7.2%, 6.5%, and 6.5%; SEM = 0.35) and digestible energy (14.8%, 10.2%, 9.3%, 10.6%, 9.8%, and 10.1% for CON, MSL, HSL, ION, CCO, and SBO, respectively; SEM = 0.62). In conclusion, both levels of lespedeza elicited similar depressions in ruminal methane emission, with a magnitude of change similar to that of an ionophore and coconut and soybean oils, and effects did not vary with week of the study.

Dietary effects on pH, temperature and ruminal methane emission by Holstein cows

El objetivo de esta investigación fue estimar la producción de metano ruminal en diferentes períodos prandiales con dos dietas características de la lechería del oriente de Antioquia (Colombia) en vacas Holstein adultas fistuladas sobre la producción de dicho gas. Para tal efecto se evaluaron dos dietas diferentes para cada vaca; una fue alimentada con forraje Cenchrus clandestinus, y la otra con forraje más 4 kg de alimento balanceado comercial por día. Durante siete días en períodos de seis horas se midió el pH y la temperatura del líquido ruminal; igualmente sus emisiones de metano usando unsensor MQ4. En cuanto a los resultados principales se puede informar que la dieta basada en forraje generó mayor producción de metano, presentando la máxima concentración dos horas después de la alimentación y la mínima concentración a las seis horas. El pH ruminal fue afectado directamente por la dieta; el menor valor se halló en la dieta mixta. No hubo evidencia de efecto alguno de la dieta sobre la temperatura media ruminal. Se concluye que la dieta basada en forraje produjo más metano comparada con la dieta mixta, lo cual se asoció también con cambios de pH, más no de temperatura. Sin embargo, no es posible asociar la producción de metano con componentes específicos de la dieta. Los alimentos o suplementos nutricionales asociados a valores de pH cambiantes durante el día pueden jugar un rol importante en la emisión de metano y en la eficiencia energética bovina.

Use of black soldier fly larvae (Hermetia illucens) to substitute soybean meal in ruminant diet: An in vitro rumen fermentation study.

Aim:This experiment aimed to evaluate substitution of soybean meal (SBM) by black soldier fly (BSF) larvae meal in a napier grass diet as performed by an in vitro rumen fermentation system.Materials and Methods:Samples of napier grass, SBM, and BSF larvae age 1 week (BSF1) and 2 weeks (BSF2) were arranged according to the following dietary treatments (dry matter [DM] basis): T1, 100% napier grass; T2, 60% napier grass + 40% SBM; T3, 60% napier grass + 40% BSF1; T4, 60% napier grass + 40% BSF2; T5, 60% napier grass + 20% SBM + 20% BSF1; and T6, 60% napier grass + 20% SBM + 20% BSF2. The samples were determined for their chemical composition and were incubated in vitro using buffered rumen fluid for 48 h at 39°C. In vitro incubation was carried out in three runs and represented by two incubation bottles per run.Results:Supplementation of BSF, both BSF1 and BSF2, increased ether extract, neutral- and acid-detergent insoluble crude protein contents of T3-T6 diets. The T3 or T4 diet resulted in lower ruminal ammonia concentration, in vitro DM digestibility, and in vitro organic matter (OM) digestibility as compared to those in T2 (p<0.05). Diet supplemented with BSF produced lower methane emission in comparison to that of supplemented with SBM (p<0.05). Diet containing BSF2 produced lower methane and methane per digestible OM than that containing BSF1 (p<0.05).Conclusion:Substitution of SBM by BSF in ruminant diet results in a lower nutritional value in vitro but with an advantage of lowering ruminal methane emission.

The role of condensed tannins in ruminant animal production: advances, limitations and future directions

ABSTRACT Tannins represent one of the most abundant polyphenolic compounds in plants. Tannins exist as a multitude of chemically unique entities in nature. The most commonly occurring tannins are typically divided into two major classes based on chemical structure: hydrolysable (HT) or condensed tannins (CT). Hydrolysable tannins are esters of gallic or ellagic acid linked to a polyol core, typically glucose. Condensed tannins or proanthocyanidins consist of flavan-3-ol subunits linked together to form oligomers and polymers. Both HT and CT are defined as astringent, medium-to-high-molecular weight polyphenolic compounds that characteristically bind and precipitate soluble proteins. The objective of this paper was to present recent advances in CT-ruminant interactions, the limitations associated with understanding and using CT in ruminant animal production, and future needs for research to further advance our knowledge of the role of CT in optimization of ruminant animal production. Condensed tannins pose some anti-nutritional problems to ruminants due to their astringent property that reduces feed intake and, consequently, animal performance. Ruminants can, however, tolerate CT by slowly adapting the ruminal microbes to the toxic effects of CT and by releasing CT-binding salivary proteins. The protein-binding ability of CT has some benefits to the ruminant due to complexes formed with essential amino acids, preventing their degradation in the rumen, but releasing them in the lower gut for absorption by the animal. Recent data have suggested increased N retention when CT is given to growing animals. There are potential benefits of using CT and HT for anthelmintic purposes due to their ability to inhibit egg hatching and larval motility of gastrointestinal nematode parasites, especially in small ruminants. Condensed tannins also bind to minerals (Al, Ca, Co, Cu, Fe, Mg, Mn, P, and Zn). Although studies with ruminants have been contradictory, it has been reported that because the CT-metal ion complex is stable over a wide pH range, CT may reduce the bioavailability of minerals. Methane mitigation by feeding CT might be the most impactful benefit for ruminant production. Many empirical equations have been developed to predict ruminal methane emissions, but very few have included CT. Future research should focus on the improvement of methodology to assess CT biological activity, interaction with other plant-specialized metabolites, and associated physiological and nutritional impacts on ruminants.

Phloroglucinol Degradation in the Rumen Promotes the Capture of Excess Hydrogen Generated from Methanogenesis Inhibition.

Strategies to manage metabolic hydrogen ([H]) in the rumen should be considered when reducing ruminant methane (CH4) emissions. However, little is known about the use of dietary treatments to stimulate rumen microorganisms capable of capturing the [H] available when CH4 is inhibited in vivo. The effects of the phenolic compound phloroglucinol on CH4 production, [H] flows and subsequent responses in rumen fermentation and microbial community composition when methanogenesis is inhibited were investigated in cattle. Eight rumen fistulated Brahman steers were randomly allocated in two groups receiving chloroform as an antimethanogenic compound for 21 days. Following that period one group received chloroform + phloroglucinol for another 16 days, whilst the other group received only chloroform during the same period. The chloroform treatment resulted in a decrease in CH4 production and an increase in H2 expelled with a shift in rumen fermentation toward higher levels of propionate and formate and lower levels of acetate at day 21 of treatment. Bacterial operational taxonomic units (OTUs) assigned to Prevotella were promoted whilst Archaea and Synergistetes OTUs were decreased with the chloroform treatment as expected. The shift toward formate coincided with increases in Ruminococcus flavefaciens, Butyrivibrio fibrisolvens, and Methanobrevibacter ruminantium species. The addition of chloroform + phloroglucinol in the rumen resulted in a decrease of H2 expelled (g) per kg of DMI and moles of H2 expelled per mol of CH4 decreased compared with the chloroform only treated animals. A shift toward acetate and a decrease in formate were observed for the chloroform + phloroglucinol-treated animals at day 37. These changes in the rumen fermentation profile were accompanied by a relative increase of OTUs assigned to Coprococcus spp., which could suggest this genus is a significant contributor to the metabolism of this phenolic compound in the rumen. This study demonstrates for the first time in vivo that under methanogenesis inhibition, H2 gas accumulation can be decreased by redirecting [H] toward alternative sinks through the nutritional stimulation of specific microbial groups. This results in the generation of metabolites of value for the host while also helping to maintain a low H2 partial pressure in the methane-inhibited rumen.

Dietary forage to concentrate ratio and sunflower oil supplement alter rumen fermentation, ruminal methane emissions, and nutrient utilization in lactating cows.

The effects of supplementing high- or low-concentrate diets with sunflower oil (SO) on rumen fermentation, nutrient utilization, and ruminal methane (CH4) emissions in lactating cows were examined. Four multiparous Nordic Red dairy cows fitted with rumen cannulae were used in a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments and 35-d periods. Experimental treatments comprised iso-nitrogenous total mixed rations based on grass silage with forage to concentrate ratio of 65:35 or 35:65 supplemented with 0 or 50 g/kg diet DM of SO. Apparent ruminal OM and starch digestibility was greater (P < 0.05) with high- than low-concentrate diets but was unaffected by SO. Inclusion of SO in high-concentrate diet decreased (P ≤ 0.05) apparent total tract OM, fiber, and GE, and apparent ruminal fiber digestibility. High-concentrate diets and SO shifted (P < 0.05) fiber digestion from rumen to the hindgut. High-concentrate diet resulted in a lower rumen pH and elevated total rumen VFA concentration compared with low-concentrate diet, whereas SO increased rumen pH and decreased rumen VFA concentration when included in high-, but not low-concentrate diet (P < 0.05 for interaction). High-concentrate diet reduced rumen ammonia-N (P < 0.01) and molar proportion of acetate to propionate (P < 0.01), and decreased (P < 0.05) ruminal CH4 emissions when expressed as g/d or g/kg OM digested in the rumen. With both low- and high-concentrate diets, SO reduced (P < 0.05) daily emissions of CH4 as g/d or g/kg OM digested in the rumen, but SO reduced CH4 emissions expressed as g/kg OM intake, OM digested in total digestive tract, energy-corrected milk or % of GE intake only with low-concentrate diet (P ≤ 0.05 for interaction). In conclusion, replacing grass silage with concentrates led to a reduction in daily ruminal CH4 emissions that were accompanied by a shift in rumen fermentation toward the synthesis of propionate, and decreases in rumen pH and fiber digestion. Sunflower oil was effective in reducing daily CH4 emissions in lactating cows which was accompanied by a noticeable lower feed intake with high- but not low-concentrate diet. Overall the effects of SO and greater proportion of concentrates in the diet on daily CH4 emissions were additive but the additivity declined or vanished when different indices of CH4 emission intensity were considered. Consequently, SO was more effective in reducing CH4 emissions when low-concentrate diet was fed.

Gene and transcript abundances of bacterial type III secretion systems from the rumen microbiome are correlated with methane yield in sheep

BackgroundRuminants are important contributors to global methane emissions via microbial fermentation in their reticulo-rumens. This study is part of a larger program, characterising the rumen microbiomes of sheep which vary naturally in methane yield (g CH4/kg DM/day) and aims to define differences in microbial communities, and in gene and transcript abundances that can explain the animal methane phenotype.MethodsRumen microbiome metagenomic and metatranscriptomic data were analysed by Gene Set Enrichment, sparse partial least squares regression and the Wilcoxon Rank Sum test to estimate correlations between specific KEGG bacterial pathways/genes and high methane yield in sheep. KEGG genes enriched in high methane yield sheep were reassembled from raw reads and existing contigs and analysed by MEGAN to predict their phylogenetic origin. Protein coding sequences from Succinivibrio dextrinosolvens strains were analysed using Effective DB to predict bacterial type III secreted proteins. The effect of S. dextrinosolvens strain H5 growth on methane formation by rumen methanogens was explored using co-cultures.ResultsDetailed analysis of the rumen microbiomes of high methane yield sheep shows that gene and transcript abundances of bacterial type III secretion system genes are positively correlated with methane yield in sheep. Most of the bacterial type III secretion system genes could not be assigned to a particular bacterial group, but several genes were affiliated with the genus Succinivibrio, and searches of bacterial genome sequences found that strains of S. dextrinosolvens were part of a small group of rumen bacteria that encode this type of secretion system. In co-culture experiments, S. dextrinosolvens strain H5 showed a growth-enhancing effect on a methanogen belonging to the order Methanomassiliicoccales, and inhibition of a representative of the Methanobrevibacter gottschalkii clade.ConclusionsThis is the first report of bacterial type III secretion system genes being associated with high methane emissions in ruminants, and identifies these secretions systems as potential new targets for methane mitigation research. The effects of S. dextrinosolvens on the growth of rumen methanogens in co-cultures indicate that bacteria-methanogen interactions are important modulators of methane production in ruminant animals.

Nitrate decreases methane production also by increasing methane oxidation through stimulating NC10 population in ruminal culture

Studies proved that addition of nitrate in rumen could lead to reduction of methane emission. The mechanism of this function was involved in the competition effect of nitrate on hydrogen consumption and the inhibitory effect of generated nitrite on methanogen proliferation. The present study investigated an alternative mechanism that denitrifying anaerobic methane oxidizing (DAMO) bacteria, DAMO archaea and anammox bacteria may co-exist in rumen, therefore, more methane can be oxidized when addition of nitrate. Ruminal batch culture model was used to test the effects of addition of 5 mM NaNO3, 4 mM NH4Cl, or both into the culture substrate on methane production, fermentation patterns, and population of methanogens, NC10 and anaerobic methanotrophic-2d (ANME-2d). Our results showed that NC10 in the ruminal culture was detected by polymerase chain reaction (PCR) when using NC10 special primer sets, and addition of nitrate reduced methane production and the relative proportions of methanogen, whereas increased the relative proportion of NC10. A combined addition of ammonia salt and nitrate did not show further inhibitory effect on methane production but accelerated nitrate removal. We did not detect DAMO archaea in ruminal culture by real-time PCR when using ANME-2d special primer sets. The present study may encourage researchers to pay more attention to methane oxidation performed by anaerobic methanotroph when studying the strategies of inhibiting ruminal methane emission.

Effect of unconventional oilseeds (safflower, poppy, hemp, camelina) on in vitro ruminal methane production and fermentation.

Dietary supplementation with oilseeds can reduce methane emission in ruminants, but only a few common seeds have been tested so far. This study tested safflower (Carthamus tinctorius), poppy (Papaver somniferum), hemp (Cannabis sativa), and camelina (Camelina sativa) seeds in vitro using coconut (Cocos nucifera) oil and linseed (Linum usitatissimum) as positive controls. All the tested oilseeds suppressed methane yield (mL g-1 dry matter, up to 21%) compared to the non-supplemented control when provided at 70 g oil kg-1 dry matter, and they were as effective as coconut oil. Safflower and hemp were more effective than linseed (21% and 18% vs. 10%), whereas the effects of poppy and camelina were similar to linseed. When methane was related to digestible organic matter, only hemp and safflower seeds and coconut oil were effective compared to the non-supplemented control (up to 11%). The level of methanogenesis and the ratios of either the n-6:n-3 fatty acids or C18:2 :C18:3 in the seed lipids were not related. Unconventional oilseeds widen the spectrum of oilseeds that can be used in dietary methane mitigation. In vivo confirmation of their methane mitigating effect is still needed, and their effects on animal performance still must be determined. © 2017 Society of Chemical Industry.

Effect of dietary formic acid on the in vitro ruminal fermentation parameters of barley-based concentrated mix feed of beef cattle

ABSTRACTThis study aimed to determine the effect of 0 (FA0) and 1, 2, 4 or 8 mL/kg (FA1, FA2, FA4 and FA8) formic acid addition to barley-based concentrated mix feed on in vitro gas kinetics [gas production from quickly soluble fraction (agas), gas production constant rate (cgas), gas production of insoluble fraction (bgas), potential gas production (a + b)gas], methane production, organic matter digestibility (OMD), metabolic energy (ME), net energy lactation (NEL), pH, ammonia-N, volatile fatty acids (VFAs), total bacteria count and number of ciliate protozoa. The in vitro cumulative gas production, cgas, bgas, (a + b)gas, ME, NEL and OMD values and ammonia-N concentration were decreased by formic acid (P < .05). Formic acid supplementation increased in vitro methane production up to about 12% (P < .05). Total bacteria count and number of protozoa and molar concentrations of total VFAs, acetic, propionic and butyric acids decreased with formic acid supplementation (P < .001). The numbers of Isotricha spp. and Dasytricha spp. increased with high formic acid (P < .001). The numbers of Diplodiniinae and Entodiniinae decreased in FA4 and FA8 groups (P < .05). The results indicated that formic acid addition to feed decreased ruminal microbiota count, digestibility, proteolysis and molar VFA values also increased ruminal methane emission. Besides, formic acid supplementation could increase energy loss during ruminal fermentation of feed.

Expression, Purification, and Characterization of (R)-Sulfolactate Dehydrogenase (ComC) from the Rumen Methanogen Methanobrevibacter millerae SM9.

(R)-Sulfolactate dehydrogenase (EC 1.1.1.337), termed ComC, is a member of an NADH/NADPH-dependent oxidoreductase family of enzymes that catalyze the interconversion of 2-hydroxyacids into their corresponding 2-oxoacids. The ComC reaction is reversible and in the biosynthetic direction causes the conversion of (R)-sulfolactate to sulfopyruvate in the production of coenzyme M (2-mercaptoethanesulfonic acid). Coenzyme M is an essential cofactor required for the production of methane by the methyl-coenzyme M reductase complex. ComC catalyzes the third step in the first established biosynthetic pathway of coenzyme M and is also involved in methanopterin biosynthesis. In this study, ComC from Methanobrevibacter millerae SM9 was cloned and expressed in Escherichia coli and biochemically characterized. Sulfopyruvate was the preferred substrate using the reduction reaction, with 31% activity seen for oxaloacetate and 0.2% seen for α-ketoglutarate. Optimal activity was observed at pH 6.5. The apparent KM for coenzyme (NADH) was 55.1 μM, and for sulfopyruvate, it was 196 μM (for sulfopyruvate the Vmax was 93.9 μmol min−1 mg−1 and kcat was 62.8 s−1). The critical role of ComC in two separate cofactor pathways makes this enzyme a potential means of developing methanogen-specific inhibitors for controlling ruminant methane emissions which are increasingly being recognized as contributing to climate change.

Scaling methane emissions in ruminants and global estimates in wild populations.

Methane (CH4) emissions by human activities have more than doubled since the 1700s, and they contribute to global warming. One of the sources of CH4 is produced by incomplete oxidation of feed in the ruminant's gut. Domestic ruminants produce most of the emissions from animal sources, but emissions by wild ruminants have been poorly estimated. This study (i) scales CH4 against body mass in 503 experiments in ruminants fed herbage, and assesses the effect of different sources of variation, using published and new data; and (ii) it uses these models to produce global estimates of CH4 emissions from wild ruminants. The incorporation of phylogeny, diet and technique of measuring in to a model that scales log10 CH4gd-1 against log10 body mass (kg), reduces the slope, from 1.075 to 0.868, making it not significantly steeper than the scaling coefficient of metabolic requirements to body mass. Scaling models that include dry matter intake (DMI) and dietary fiber indicate that although both increase CH4, dietary fiber depresses CH4 as the levels of DMI increases. Cattle produces more CH4 per unit of DMI than red deer, sheep or goat, and there are no significant differences between CH4 produced by red deer and sheep. The average estimates of global emissions from wild ruminants calculated using different models are smaller (1.094-2.687Tgy-1) than those presented in the reports of the Intergovernmental Panel on Climate Change (15Tgyr-1). Potential causes to explain such discrepancy are the uncertainty on the world's wild ruminant population size, and the use of methane output from cattle, a high methane producer, as representative methane output of wild ruminants. The main limitation researchers' face in calculating accurate global CH4 emissions from wild ungulates is a lack of reliable information on their population sizes.

0720 Effects of feeding forage and concentrate, separately or as a total mixed ration, on ruminal methane emission, fermentation characteristics, and total tract digestibility

0720 Effects of feeding forage and concentrate, separately or as a total mixed ration, on ruminal methane emission, fermentation characteristics, and total tract digestibility

Nutrient composition, rate of fermentation andin vitrorumen methane output from tropical feedstuffs

SUMMARYIn vitrorumen methane output (IRMO) of over 200 feed/feed mix samples representing approximately 74 feed types was investigated in a series of completely randomized experiments. The samples comprised dry fodder, grass, tree leaves, cultivated grasses, cereal by-products, cereal grains, oilseed/meals, compound feeds and total mixed rations (TMRs) from the tropical regions. These samples were subjected to threein vitrogas production tests at 39 °C in 100 ml Heberle syringes. The first incubation was conducted with 200 mg dry matter (DM) substrate for 96 h to determine half-time gas production (t1/2, h) value of each sample. The second and third incubations were carried out simultaneously. The second incubation was done with 200 mg DM substrate untilt1/2time to determine IRMO and third with 500 mg DM to estimatein vitrodry matter digestibility (IVDMD) of each samples, respectively. The IRMO was expressed as ml/100 mg digestible substrate. Crude protein content (g/kg DM) was lowest in dry fodder samples and highest in oilseed meals, whereas it was similar in local grass and tree leaves. The IVDMD values ranged from 0·48 to 0·87; the lowest digestibility was recorded in tree leaves. The potential gas production (PGP, ml/200 mg DM) ranged from 9·76 to 61·3. The PGP from grasses and compound feeds was similar, whereas it was lowest in tree leaves. The rate constant (mg/h) was maximum in compound feed followed by oilseed meal. The rate constant was similar among other group of feedstuffs. Thet1/2time ranged from 9·8 to 19·4 h. The highestt1/2time was recorded in local grass samples followed by dry fodder and cultivated grasses. However, they were similar among tree leaves, cereal grains, by-products and compound feeds. The methane % in the total gas varied from 9·79 (tree leaves) to 20·2 (local grasses). Among straw, IRMO varied from 3·88 (Zea maysfodder) to 12·0 (Sorghum vulgare) and it was lower in fruit tree leaves than cultivated grasses. Among protein and energy sources, IRMO was higher in cereal by-products as compared with cereal grains, oil meals and compound feed. The IRMO was similar among TMR, irrespective of the composition of the concentrate mixture. Nevertheless, it varied with the amount of concentrate in the TMR. This is the first exhaustive data on IRMO from the tropical region. Because of the substantial amount of dietary gross energy lost in methane, knowledge of the methane output from these feed ingredients will help in formulating low methane emitting diets for ruminants. Incorporation of tropical tree leaves in the diets and feeding TMR are potential strategies to reduce enteric methane emission in ruminants.