Decreased CH4 Production Research Articles

Potential of Molecular Weight and Structure of Tannins to Reduce Methane Emissions from Ruminants: A Review.

Simple SummaryRegardless of the production system adopted, ruminant livestock contribute to greenhouse emissions that are associated with climate change. Among the greenhouse gases, enteric methane produced from the rumen is of the greatest concern because it is the largest single source of livestock emissions. Among the different dietary strategies examined to decrease methanogenesis in ruminants, the use of tannins shows promise, but has received only moderate attention. However, tannins are abundant in both tropical and temperate plants and so are widely available globally and may be an economical approach for livestock producers to mitigate enteric methane emissions. This review explores the challenges and opportunities of using dietary tannins to reduce enteric methane emissions from ruminants.There is a need to reduce enteric methane (CH4) to ensure the environmental sustainability of ruminant production systems. Tannins are naturally found in both tropical and temperate plants, and have been shown to consistently decrease urinary nitrogen (N) excretion when consumed by ruminants. However, the limited number of in vivo studies conducted indicates that the effects of tannins on intake, digestibility, rumen fermentation, CH4 production and animal performance vary depending on source, type, dose, and molecular weight (MW). There are two main types of tannin in terrestrial plants: condensed tannin (CT; high MW) and hydrolysable tannin (HT; low MW). Consumption of CT and HT by ruminants can reduce N excretion without negatively affecting animal performance. High MW tannins bind to dietary protein, while low MW tannins affect rumen microbes, and thus, irrespective of type of tannin, N excretion is affected. The structure of high MW tannin is more diverse compared with that of low MW tannin, which may partly explain the inconsistent effects of CT on CH4 production reported in in vivo studies. In contrast, the limited number of in vivo studies with low MW HT potentially shows a consistent decrease in CH4 production, possibly attributed to the gallic acid subunit. Further in vivo studies are needed to determine the effects of tannins, characterized by MW and structural composition, on reducing CH4 emissions and improving animal performance in ruminants.

Treatment of feces from beef cattle fed the enteric methane inhibitor 3-nitrooxypropanol.

The study evaluated the residual effect of the known enteric methane inhibitor 3-nitrooxypropanol (3NOP) on anaerobic digestion of cattle feces (feces) in a CH4 potential batch test and two consecutive runs of an anaerobic leach bed reactor at a solids retention time of 40 days. The feces used in this study were collected from beef cattle fed forage- (backgrounding) or grain- (finishing) based diets supplemented with 3NOP in feedlot and metabolism studies. The results showed that CH4 yields were not significantly different from treatments using control feces and feces collected from cattle fed a diet supplemented with 3NOP in both CH4 potential and leach bed studies. Spiking feces with 200 mg 3NOP kg-1 dry matter decreased CH4 production rate by 8.0-18.1% estimated from the Gompertz equation, increased the lag phase time (0.4-3.4 d) in all the treatments, while there was no significant difference in the overall CH4 yield. Results from this study showed that 3NOP can be used as an effective enteric CH4 inhibitor with no residual effect on anaerobic digestion.

In vitro evaluation of utilisable crude protein and methane production for a diet in which grass silage was replaced by different levels and fractions of extracted seaweed proteins

Utilisable crude protein (uCP), methane (CH4) production and other fermentation parameters were analysed in vitro for a diet in which grass silage was replaced by different levels of seaweed protein fractions prepared from three seaweed species: Saccharina latissima, Alaria esculenta and Palmaria palmata. Ten fractions from these three species in which the protein content had been increased and the salt content reduced by simple processing were tested, with inclusion levels in the diet based on the nitrogen content of the fractions. Following an extraction procedure, four fractions from Saccharina latissima, three from Alaria esculenta and one from Palmaria palmata, were incrementally included in the diet by replacing high quality silage with approximately 0, 0.15, 0.30 and 0.45 g/g DM, while two high-protein fractions of Palmaria palmata were tested at replacement levels of 0, 0.075, 0.15 and 0.225 g/g DM. To estimate fermentation parameters, 500 mg of each diet were incubated in bottles with 60 mL buffered rumen fluid. Estimated uCP increased linearly with increasing replacement rate of grass silage with seaweed protein fractions (from 158 g/kg DM to 206 g/kg DM on average for all fractions). Increasing protein fraction from the brown seaweed Saccharina latissima in the diet significantly increased true organic matter digestibility (OMD) (from on average 0.786 to 0.821). Organic matter digestibility decreased with increasing level of Alaria esculenta fractions (from on average 0.785 to 0.733), which also gave a linear decrease in CH4 production (from on average 45.3 to 38.5 mL/g organic matter). As a result of decreased CH4 production and OMD, total volatile fatty acid concentration decreased with increasing level of Alaria esculenta fractions (from on average 69.5 to 63.0 mmol/L). Thus, positive and species-specific effects of seaweed on estimated uCP and fermentation parameters were observed in vitro when protein fractions remaining after an extraction procedure on seaweed partly replaced grass silage in the feed ration.

Methanogenic potential of tropical feeds rich in hydrolyzable tannins1,2.

The present study was carried out to determine the effect of Acacia nilotica, a tropical plant rich in hydrolyzable tannins (HT), on rumen fermentation and methane (CH4) production in vitro. We used leaves and pods from A. nilotica alone and combined. The combination of HT from A. nilotica leaves and pods and condensed tannins (CT) from Calliandra calothyrsus and Leucaena leucocephala were also evaluated to assess potential differences in biological activity between HT and CT. Four series of 24-h incubations were performed using rumen contents of 4 sheep fed a tropical grass (natural grassland based on Dichanthium spp.). A first experiment tested different levels of replacement of this tropical forage (control [CTL] without tannins) by A. nilotica leaves or pods: 0:100, 25:75, 50:50, 75:25 and 100:0. A second experiment tested the mixture of A. nilotica leaves and pods in different proportions: 100:0, 75:25, 50:50, 25:75, and 0:100. A third experiment tested the 50:50 combination of A. nilotica leaves or pods with C. calothyrsus and L. leucocephala. Acacia nilotica pods and leaves had a high content of HT (350 and 178 g/kg DM, respectively), whereas C. calothyrsus and L. leucocephala had a high content of CT (361 and 180 g/kg DM, respectively). The inclusion of HT from A. nilotica leaves and pods decreased CH4 production dose-dependently (P < 0.01). Total replacement of the CTL by A. nilotica decreased CH4 production by 64 and 55% with leaves and pods, respectively. Pods were richer in HT than leaves, but their antimethanogenic effect did not differ (P > 0.05). Although A. nilotica leaves and pods inhibited fermentation, as indicated by the lower gas production and VFA production (P < 0.01), this effect was less pronounced than for CH4. Volatile fatty acid production decreased by 12% in leaves and by 30% in pods when compared with the CTL alone. Positive associative effect was reported for VFA, when HT-rich sources and CT-rich sources were mixed. Combining the 2 sources of HT did not show associative effects on fermentation or CH4 production (P > 0.05). Hydrolyzable tannin-rich sources were more effective in suppressing methanogenesis than CT-rich sources. Our results show that HT-rich A. nilotica leaves and pods have the potential to reduce ruminal CH4 production.

Use of gallic acid and hydrolyzable tannins to reduce methane emission and nitrogen excretion in beef cattle fed a diet containing alfalfa silage1,2.

The objective of this study was to determine the effects of different forms of hydrolyzable tannin [HT; source (chestnut, CN; tannic acid, TA); subunit (gallic acid, GA)] on apparent total-tract digestibility, methane (CH4) production, and nitrogen (N) utilization in beef cattle fed an alfalfa silage-based diet. Eight ruminally cannulated heifers with an initial BW of 480 ± 29.2 kg (mean ± SD) were used in a double 4 × 4 Latin square experiment. The experiment consisted of four 28-d periods (14-d adaptation, 14-d measurements) and a 7-d washout between periods. The animals received a basal diet with 19.8% CP (DM basis) content containing 75% alfalfa silage, 20% barley silage, and 5% supplement (DM basis) with or without different forms of HT. The dietary treatments were as follows: control (no HT), GA (1.5% of diet DM), TA (1.5% of diet DM), and CN (2% of diet DM). Animals were fed 95% of their ad libitum intake during the measurement phase. Total fecal excretion was collected for 4 d, CH4 was measured for 72 h using respiration chambers, and ruminal fermentation variables and plasma urea N (PUN) concentration were measured on 2 nonconsecutive days before and after feeding. The restricted DM (DMI; 10.79 ± 1.076 kg/d) and nutrient intakes did not differ (P ≥ 0.22) among treatments. Furthermore, apparent DM digestibility (60.3 ± 0.86%) was not affected (P = 0.20) by treatment, but CP digestibility decreased for TA and CN compared with control and GA treatments (63.1 vs. 69.0%; P < 0.001). Total VFA concentration tended (P = 0.089) to increase for GA compared with control and TA (134 vs. 125 and 126 mM) and intermediate for CN (129 mM). The PUN concentration was lower for all HT treatments compared with control (196 vs. 213 mg/L; P = 0.02). Both TA and CN increased the proportion of N excreted in feces and decreased the proportion in urine compared with control and GA (43.9% vs. 37.8% and 56.1% vs. 62.2%; respectively; P < 0.001). However, the proportion of urea N in urinary N decreased for all HT treatments compared with control (47.2% vs. 51.2%; P = 0.02). Also, GA tended to decrease CH4/DMI (20.4 vs. 22.3 g/kg DMI; P = 0.07) and decreased the proportion of GE intake emitted as CH4 (5.16 vs. 5.71%; P = 0.04) compared with control. Thus, among the different forms of HT applied to a high-protein alfalfa silage-based diet, both TA and CN had no effect on CH4 production, but decreased CP digestibility and shifted N excretion from urine to feces, whereas GA (i.e., HT subunit) decreased CH4 production and decreased the proportion of urea N in urinary N in beef cattle without affecting CP digestibility. Thus, feeding the HT subunit, GA, has the potential to decrease environment impact of ruminants (lower CH4 and ammonia emissions), without decreasing animal performance.

Bovicins: The Bacteriocins of Streptococci and Their Potential in Methane Mitigation.

Bovicin is a type AII lantibiotic, possessing two β-methyllanthionine and a disulfide bridge encoded by bovA gene hitherto unknown a couple of decades ago. Bacteriocins can be useful in directly inhibiting methanogens and/or redirecting H2 to other reductive microorganisms, in particular, propionate producers or reductive acetogens. So far, the role of nisin and bovicin to suppress greenhouse gas (GHG) production under in vitro conditions has been documented. GHG emissions from ruminants are a threat to the environment, because of their role in global warming as well as in climate change. Methane (CH4) produced from livestock farming practices is a potent GHG, comprising 18% of total GHG emissions in the world. Therefore, minimizing enteric CH4 production is quite essential from both the economical livestock production as well as environment perspectives. Strategies for the abatement of CH4 have provided two-way opportunities, viz., improved livestock productivity and reduced GHG emissions. In the past, different strategies have been proposed and tested to mitigate CH4, such as the dietary composition of feeds, ionophores, antibiotics, vaccines, analogues, probiotics, and secondary metabolites of plants and fungi. However, quite a few of these strategies have been adopted at farm level due to their varied effect on animal health and/or residues on animal products. The use of bacteriocins might have potential in inhibiting methanogens in the rumen. A bacteriocin produced by Streptococcus bovis (an isolate from rumen) named bovicin HC5 has been exhibited to decrease CH4 production to an extent of 50%. In this review, authors intend to discuss the sources, structure, biochemical properties, and antimicrobial spectra of bovicins, besides the potential applications with special reference to CH4 mitigation.

Effects of the inclusion of Moringa oleifera seed on rumen fermentation and methane production in a beef cattle diet using the rumen simulation technique (Rusitec)

Moringa oleifera seeds are currently being used as a livestock feed across tropical regions of the world due to its availability and palatability. However, limited knowledge exists on the effects of the raw seeds on ruminant metabolism. As such, the rumen stimulation technique was used to evaluate the effects of substituting increasing concentrations of ground Moringa seeds (0, 100, 200 and 400 g/kg concentrate dry matter (DM)) in the diet on rumen fermentation and methane production. Two identical, Rusitec apparatuses, each with eight fermenters were used with the first 8 days used for adaptation and days 9 to 16 used for measurements. Fermenters were fed a total mixed ration with Urochloa brizantha as the forage. Disappearance of DM, CP, NDF and ADF linearly decreased (P<0.01) with increasing concentrations of Moringa seeds in the diet. Total volatile fatty acid production and the acetate to propionate ratio were also linearly decreased (P<0.01). However, only the 400 g/kg (concentrate DM basis) treatment differed (P<0.01) from the control. Methane production (%), total microbial incorporation of 15N and total production of microbial N linearly decreased (P<0.01) as the inclusion of Moringa seeds increased. Though the inclusion of Moringa seeds in the diet decreased CH4 production, this arose from an unfavourable decrease in diet digestibility and rumen fermentation parameters.

The influence of copper levels on in vitro ruminal fermentation, bacterial growth and methane production.

Copper (Cu) is an essential microelement to the health and proper functioning of metabolic processes in animals, but the particular function of Cu in fermentation processes and the formation of methane (CH4 ) in the rumen have been poorly analyzed. The innovative aspect of this study was to investigate the effects of high doses of Cu as copper sulfate on in vitro ruminal degradation, fermentation patterns, and CH4 production. There was a decrease (P < 0.04) on in vitro dry matter (DM) and organic matter degradability from 60 to 100 µg Cu/g DM. Ammonia concentration decreased drastically with increasing Cu levels (linear effect, P < 0.01). Total bacteria and volatile fatty acids (quadratic effect, P < 0.02) were reduced with 80 and 100 µg Cu/g DM. Methane production (milliliters per gram digestible organic matter) was decreased when dosages of Cu were increased (linear effect, P < 0.003). Overall, the addition of increasing levels of Cu to 40 µg Cu/g DM did not have an adverse impact on ruminal bacteria growth and decreased CH4 production, without affecting the ruminal kinetics. © 2018 Society of Chemical Industry.

Unconventional Vegetable Oils for a Reduction of Methanogenesis and Modulation of Ruminal Fermentation

The objective of this study was to evaluate the use of vegetable oils from plants grown in Brazil, first using the in vitro batch culture, and then evaluating the oil with methane (CH4) reducing potential in an in vivo experiment. The in vitro experiment was conducted as a completely randomized design using the seven contrasting oils. Treatments consisted of a control and 3 increasing concentrations (0, 1, 2, and 5% v/v) of oil added to a tifton 85 hay samples. All vegetable oils linearly decreased (P < 0.01) gas production after 24 h of incubation, with the greatest reduction when 5% of oil was included into the diet. Açaí and buriti had no effect of CH4 (% or mL/g DM incubated) however carrot, macaúba, basil, passionflower, and pequi oil all linearly decreased (P < 0.01) CH4 production with increasing inclusion rate of oil. Pequi oil resulted in the largest decrease in CH4 production (mL/g DM incubated) after 24 h of in vitro incubation. The objective of the in vivo experiment was to evaluate the effects of pequi oil on nutrient digestibility, CH4 production, and rumen fermentation parameters in wethers fed a hay-based diet. The experiment was conducted as a 2 × 2 Latin Square design using 4 Dorper wethers (63.4 ± 1.46 kg body weight). There were 2 experimental periods of 21 d each, with d 1–14 used for diet adaptation and d 15–21 for measurements and collections. The treatments consisted of a control diet and pequi oil fed at 70 g per animal per day. The addition of pequi oil to the diet had no effect on feed intake or the digestibility of nutrients, however there was a numerical decrease in the population of cellulolytic bacteria. There was a tendency (P = 0.06) for pequi oil addition to decrease CH4 production (g/d) by 17.5%. From this study, we can conclude that pequi oil may be used as a suitable oil for reducing CH4 production from ruminants, with no negative effects on intake or digestibility.

Long-term influence of trace element deficiency on anaerobic mono-digestion of chicken manure

Recent findings showed that some trace elements essential for anaerobic digestion might be deficient in chicken (laying hens) manure. In this study, the long-term influence of trace element deficiency on anaerobic mono-digestion of chicken manure was investigated. Three bench-scale anaerobic reactors were operated with or without trace element supplementation. As trace element, only Se or a mix containing Co, Mo, Ni, Se, and W was added to the reactors. The results revealed that in anaerobic digestion of chicken manure at total ammonium nitrogen concentrations over 6000 mg L−1, Se supplementation was critical but not sufficient alone for long-term stable CH4 production. Addition of a mix consisting of Co, Mo, Ni, Se and W resulted in a more stable digestion performance. Daily trace element mix supplementation promoted the hydrogenotrophic Methanoculleus bourgensis, which is an ammonia tolerant methanogen. The decrease in the relative abundance of Methanoculleus detected after termination of trace element addition and resulted in accumulation of acetate and propionate that followed by a significant decrease in CH4 production.

The effect of encapsulated nitrate and monensin on ruminal fermentation using a semi-continuous culture system.

Because enteric methane (CH4) production from ruminants represents a source of greenhouse gas emissions and an energy loss for the host animal alternatives to minimize emissions is a current research priority. Seven 37-d trials tested the effect of encapsulated nitrate (EN) and sodium monensin (MON) in diets commonly fed to dairy (DAIRY; 50:50 forage to concentrate; four trials) and beef cattle (BEEF; 15:85 forage to concentrate; three trials) on rumen fermentation and CH4 production using a semi-continuous fermentation system. A 3 × 2 factorial arrangement was used and additives (0, 1.25, and 2.5% of EN; 0 and 4 mg/L of MON) were tested alone and combined (EN + MON) totaling six treatments. Rumen fluid was pooled from five nonadapted lactating cows fed 50:50 forage to concentrate diet 3 h after morning feeding, and 1 L of processed inoculum was transferred to 2.2-L vessels. Treatment diets were added to nylon bags which remained in the anaerobic fermentation of mixed rumen microorganisms for 48 h. Nitrate decreased CH4 production in DAIRY (24.7 vs. 32.1 mM/d; P < 0.01) and BEEF trials (33.5 vs. 43.5 mM/d; P < 0.01). Methane production was decreased by MON in DAIRY (26.3 vs. 32.1; P < 0.01) and BEEF (26.6 vs. 43.5 mM/d; P < 0.01). The combination of EN + MON further decreased CH4 in DAIRY (21.3 vs. 32.1 mM/d; P = 0.03) and BEEF (19.3 vs. 43.5 mM/d; P = 0.01). Nitrate did not affect major VFA production in DAIRY and BEEF trials, but significantly decreased digestion of protein (96.8 vs. 97.6%; P < 0.01) and starch (79.0 vs. 80.4%; P < 0.01) in DAIRY and NDF (29.3 vs. 32.5%; P < 0.01) and starch (88.5 vs. 90.3%; P < 0.01) in BEEF. Monensin significantly affected VFA pattern with an increase in propionate (P < 0.01) and a decrease on acetate (P < 0.01) production with consequent decrease on acetate-to-propionate ratio in DAIRY (1.6 vs. 2.0; P < 0.01) and BEEF (1.6 vs. 1.9; P < 0.01). Monensin decreased NDF digestion in BEEF only (29.3 vs. 32.5 %; P < 0.01). Significant concentrations of nitrate and nitrite were detected only for EN and EN + MON (P < 0.01). Nitrate and MON effectively decreased CH4 production when fed separately and the combination of additives additively decreased CH4 production.

Effects of pure plant secondary metabolites on methane production, rumen fermentation and rumen bacteria populations in vitro.

In this study, the effects of seven pure plant secondary metabolites (PSMs) on rumen fermentation, methane (CH4 ) production and rumen bacterial community composition were determined. Two in vitro trials were conducted. In trial 1, nine concentrations of 8-hydroxyquinoline, α-terpineol, camphor, bornyl acetate, α-pinene, thymoquinone and thymol were incubated on separate days using in vitro 24-hr batch incubations. All compounds tested demonstrated the ability to alter rumen fermentation parameters and decrease CH4 production. However, effective concentrations differed among individual PSMs. The lowest concentrations that reduced (p<.05) CH4 production were as follows: 8mg/L of 8-hydroxyquinoline, 120mg/L of thymoquinone, 240mg/L of thymol and 480mg/L of α-terpineol, camphor, bornyl acetate and α-pinene. These concentrations were selected for use in trial 2. In trial 2, PSMs were incubated in one run. Methane was decreased (p<.05) by all PSMs at selected concentrations. However, only 8-hydroxyquinoline, bornyl acetate and thymoquinone decreased (p<.05) CH4 relative to volatile fatty acids (VFAs). Based on denaturing gradient gel electrophoresis analysis, different PSMs changed the composition of bacterial communities to different extents. As revealed by Ion Torrent sequencing, the effects of PSMs on relative abundance were most pronounced in the predominant families, especially in Lachnospiraceae, Succinivibrionaceae, Prevotellaceae, unclassified Clostridiales and Ruminococcaceae. The CH4 production was correlated negatively (-.72; p<.05) with relative abundance of Succinivibrionaceae and positively with relative abundance of Ruminococcaceae (.86; p<.05). In summary, this study identified three pure PSMs (8hydroxyquinoline, bornyl acetate and thymoquinone) with potentially promising effects on rumen CH4 production. The PSMs tested in this study demonstrated considerable impact on rumen bacterial communities even at the lowest concentrations that decreased CH4 production. The findings from this study may help to elucidate how PSMs affect rumen bacterial fermentation.

Environmental risk assessment of steel-making slags and the potential use of LD slag in mitigating methane emissions and the grain arsenic level in rice (Oryza sativa L.)

Over the past decades, with increasing steel manufacturing, the huge amount of by-products (slags) generated need to be reused in an efficient way not only to reduce landfill slag sites but also for sustainable and eco-friendly agriculture. Our preliminary laboratory study revealed that compared to blast furnace slag, electric arc furnace slag and ladle furnace slag, the Linz-Donawitz converter (LD) slag markedly decreased CH4 production rate and increased microbial activity. In the greenhouse experiment, the LD slag amendment (2.0 Mg ha−1) significantly (p < 0.05) increased grain yield by 10.3–15.2%, reduced CH4 emissions by 17.8–24.0%, and decreased inorganic As concentrations in grain by 18.3–19.6%, compared to the unamended control. The increase in yield is attributed to the increased photosynthetic rates and increased availability of nutrients to the rice plant. Whereas, the decrease in CH4 emissions could be due to the higher Fe availability in the slag amended soil, which acted as an alternate electron acceptor, thereby, suppressed CH4 emissions. The more Fe-plaque formation which could adsorb more As and the competitive inhibition of As uptake with higher availability of Si could be the reason for the decrease in As uptake by rice cultivated with LD slag amendment.

Cattle manure composting: Shifts in the methanogenic community structure, chemical composition, and consequences on methane production potential in a rice paddy

Compost application has been considered to be one of the most promising methods for sustaining soil quality and crop productivity and possibly attenuates the impact of methane (CH4) emission in rice paddies. The physico-chemical and biological characteristics of manure may vary, depending on the maturity of the compost. Therefore, compost obtained from different stages of maturation could differentially influence CH4 production in rice paddies following input into the fields. In composting samples, we investigated the effect of composting on alterations in physico-chemical characteristics and changes in methanogenic abundance and community structure in manure during the maturation process using a conventional static chamber method. Thereafter, CH4 production potential was monitored in soil samples amended with compost obtained from different composting stages (0 as a starting material, 7, 14, 21, 28, and 35 days after installation) via an incubation experiment. The results show that manure composting significantly decreased the methanogenic abundance and altered the methanogenic community structure by qPCR and T-RFLP analyses, respectively. The physico-chemical properties, such as labile carbon (C) and nitrogen (N) availabilities in manure, were gradually changed due to high temperature and oxygen supplement. These changes result in decreasing CH4 production in a rice field soil amended with composts. Our results suggest that composting is a promising approach to mitigate the impact of CH4 emissions in rice paddy fields with manure. In conclusion, composting should be indispensable for mitigating the impact of CH4 emission in manure-amended paddy soil during cultivation.

Changes in Glucose Fermentation Pathways as a Response to the Free Ammonia Concentration in Microbial Electrolysis Cells.

When a mixed-culture microbial electrolysis cell (MEC) is fed with a fermentable substrate, such as glucose, a significant fraction of the substrate's electrons ends up as methane (CH4) through hydrogenotrophic methanogenesis, an outcome that is undesired. Here, we show that free ammonia-nitrogen (FAN, which is NH3) altered the glucose fermentation pathways in batch MECs, minimizing the production of H2, the "fuel" for hydrogenotrophic methanogens. Consequently, the Coulombic efficiency (CE) increased: 57% for 0.02 g of FAN/L of fed-MEC, compared to 76% for 0.18 g of FAN/L of fed-MECs and 62% for 0.37 g of FAN/L of fed-MECs. Increasing the FAN concentration was associated with the accumulation of higher organic acids (e.g., lactate, iso-butyrate, and propionate), which was accompanied by increasing relative abundances of phylotypes that are most closely related to anode respiration (Geobacteraceae), lactic-acid production (Lactobacillales), and syntrophic acetate oxidation (Clostridiaceae). Thus, the microbial community established syntrophic relationships among glucose fermenters, acetogens, and anode-respiring bacteria (ARB). The archaeal population of the MEC fed 0.02 g FAN/L was dominated by Methanobacterium, but 0.18 and 0.37 g FAN/L led to Methanobrevibacter becoming the most abundant species. Our results provide insight into a way to decrease CH4 production and increase CE using FAN to control the fermentation step, instead of inhibiting methanogens using expensive or toxic chemical inhibitors, such as 2-bromoethanesulfonic acid.

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.

Effects of illite supplementation on invitro and invivo rumen fermentation, microbial population and methane emission of Hanwoo steers fed high concentrate diets.

This study was conducted to evaluate the effects of feeding supplemental illite to Hanwoo steers on methane (CH4 ) emission and rumen fermentation parameters. An invitro ruminal fermentation technique was conducted using a commercial concentrate as substrate and illite was added at different concentrations as treatments: 0%, 0.5%, 1.0%, and 2.0% illite. Total volatile fatty acids (VFA) were different (P<0.05) at 24h of incubation where the highest total VFA was observed at 1.0% of illite. Conversely, lowest CH4 production (P<0.01) was found at 1.0% of illite. In the invivo experiment, two diets were provided, without illite and with addition of 1% illite. An automated head chamber (GreenFeed) system was used to measure enteric CH4 production. Cattle received illite supplemented feed increased (P<0.05) total VFA concentrations in the rumen compared with those fed control. Feeding illite numerically decreased CH4 production (g/day) and yield (g/kg dry matter intake). Rumen microbial population analysis indicated that the population of total bacteria, protozoa and methanogens were lower (P<0.05) for illite compared with the control. Accordingly, overall results suggested that feeding a diet supplemented with 1% illite can have positive effects on feed fermentation in the rumen and enteric CH4 mitigation in beef cattle.

Linseed oil and DGAT1 K232A polymorphism: Effects on methane emission, energy and nitrogen metabolism, lactation performance, ruminal fermentation, and rumen microbial composition of Holstein-Friesian cows

Complex interactions between rumen microbiota, cow genetics, and diet composition may exist. Therefore, the effect of linseed oil, DGAT1 K232A polymorphism (DGAT1), and the interaction between linseed oil and DGAT1 on CH4 and H2 emission, energy and N metabolism, lactation performance, ruminal fermentation, and rumen bacterial and archaeal composition was investigated. Twenty-four lactating Holstein-Friesian cows (i.e., 12 with DGAT1 KK genotype and 12 with DGAT1 AA genotype) were fed 2 diets in a crossover design: a control diet and a linseed oil diet (LSO) with a difference of 22 g/kg of dry matter (DM) in fat content between the 2 diets. Both diets consisted of 40% corn silage, 30% grass silage, and 30% concentrates (DM basis). Apparent digestibility, lactation performance, N and energy balance, and CH4 emission were measured in climate respiration chambers, and rumen fluid samples were collected using the oral stomach tube technique. No linseed oil by DGAT1 interactions were observed for digestibility, milk production and composition, energy and N balance, CH4 and H2 emissions, and rumen volatile fatty acid concentrations. The DGAT1 KK genotype was associated with a lower proportion of polyunsaturated fatty acids in milk fat, and with a higher milk fat and protein content, and proportion of saturated fatty acids in milk fat compared with the DGAT1 AA genotype, whereas the fat- and protein-corrected milk yield was unaffected by DGAT1. Also, DGAT1 did not affect nutrient digestibility, CH4 or H2 emission, ruminal fermentation or ruminal archaeal and bacterial concentrations. Rumen bacterial and archaeal composition was also unaffected in terms of the whole community, whereas at the genus level the relative abundances of some bacterial genera were found to be affected by DGAT1. The DGAT1 KK genotype was associated with a lower metabolizability (i.e., ratio of metabolizable to gross energy intake), and with a tendency for a lower milk N efficiency compared with the DGAT1 AA genotype. The LSO diet tended to decrease CH4 production (g/d) by 8%, and significantly decreased CH4 yield (g/kg of DM intake) by 6% and CH4 intensity (g/kg of fat- and protein-corrected milk) by 11%, but did not affect H2 emission. The LSO diet also decreased ruminal acetate molar proportion, the acetate to propionate ratio, and the archaea to bacteria ratio, whereas ruminal propionate molar proportion and milk N efficiency increased. Ruminal bacterial and archaeal composition tended to be affected by diet in terms of the whole community, with several bacterial genera found to be significantly affected by diet. These results indicate that DGAT1 does not affect enteric CH4 emission and production pathways, but that it does affect traits other than lactation characteristics, including metabolizability, N efficiency, and the relative abundance of Bifidobacterium. Additionally, linseed oil reduces CH4 emission independent of DGAT1 and affects the rumen microbiota and its fermentative activity.

Effects of Schizochytrium microalgae and sunflower oil as sources of unsaturated fatty acids for the sustainable mitigation of ruminal biogases methane and carbon dioxide

Mitigation of methane (CH4) and carbon dioxide (CO2) emissions as well as ruminal fermentation parameters of a total mixed ration in the presence of Schizochytrium microalgae (SA) and sunflower oil (SO) or their mixture (SASO) as unsaturated fatty acid sources was investigated. Rumen liquor from two rumen cannulated Holstein steers and two rumen cannulated Creole goats was used as inoculum. Interactions between inoculum source × additive type, and inoculum source × additive type × dose were observed for gas, CH4 and CO2 production and fermentation parameters. Additives affected the fermentation parameters in a dose-dependent manner. With goats’ inoculum, the inclusion of SO (1, 2, 4, 5%), SA (2, 3, 5%) and SASO (1, 3%) increased gas production (GP) and decreased the rate of GP, while with the steer inoculum, SO at 1 and 4% increased GP and the rate of GP. All levels of SA and SASO decreased the asymptotic GP and increased the rate of GP. The goat inoculum decreased CH4 at different doses of SO, SA and SASO whereas the steer inoculum decreased CH4 production. At all doses, additives decreased fermentation pH, protozoal counts, and increased ammonia-N, DM degradability and total bacterial counts. Sunflower oil (i.e., SO) at 1–3%, SA at 1–2%, and SASO at 1–2% were the most efficacious in the nutrition of goats, compared with SO at 1 to 2 in steers. The results suggest that Schizochytrium microalgae and sunflower oil could be a valuable means of sustainably mitigating CH4 and CO2 emissions for improved environmental conditions.

Moringa oleifera leaf meal as an environmental friendly protein source for ruminants: Biomethane and carbon dioxide production, and fermentation characteristics

Ruminal fermentation produces methane (CH4) and carbon dioxide (CO2) which contribute to global warming. Therefore, several enteric CH4 and CO2 mitigation strategies have been explored recently. In this trial the effect of replacing soybean meal, as the sole protein source in a control total mixed ration (TMR) with Moringa oleifera leaf meal (MLM) at different levels, on ruminal fermentation characteristics were studied. M. oleifera leaf meal replaced (g/100 g DM): 0 (TMR0, control), 10 (TMR10), 20 (TMR20), 30 (TMR30), 40 (TMR40), 50 (TMR50), 60 (TMR60), 70 (TMR70), 80 (TMR80), 90 (TMR90), and 100 (TMR100) of soybean meal in the rations. Rations were incubated for 48 h using rumen inoculums from goats and steers. Some interactions between inoculum × TMR were observed (P < 0.05) for gas production (GP) parameters, CH4 production, and fermentation profile. Moreover, most parameters determined responded differently between animal species. Rations containing MLM decreased the asymptotic GP (P < 0.01), while they increased (P < 0.01) the rate of GP and lag of GP with both inoculums. Decreased (P < 0.05) CH4 production and increased CO2 production (P < 0.05) were observed when MLM replaced soybean meal. Diets containing MLM decreased (P < 0.05) ruminal ammonia-N and total protozoal number, while increasing (P < 0.05) total bacterial number with both goat and steer inoculums. Replacing soybean meal with MLM increased (P < 0.05) fermentation pH, but decreased (P < 0.05) organic matter degradability (OMD) with goat inoculum. Conversely, a declined (P < 0.05) in SCFA concentrations, and enhanced (P < 0.05) OMD and DM degradability compared with the control diet was observed with diets containing MLM. It is concluded that replacing soybean meal in goat and steer diets negatively affected the nutritive value of diets but decreased CH4 production. From an environmental standpoint, the replacement of soybean meal with MLM is a potential sustainable strategy to reduce CH4 production from goats and steers, and thus mitigate greenhouse gas emissions. Goat inoculum was more efficient in reducing CH4 production than that of steers.