Decreased Methane Production Research Articles

Brazilian propolis extract used as an additive to decrease methane emissions from the rumen microbial population in vitro.

Propolis is a product that is rich in phenolic compounds and can be utilized in animal nutrition as a dietary additive. In this study, the effects of a Brazilian green propolis extract on rumen fermentation and gas production were determined. The fate of propolis phenolic compounds in the rumen medium was also investigated. Fermentation was done in 24-h batches over three periods. Inoculates were obtained from cows fed on grassland hay and concentrate. Propolis extract in a hydroalcoholic solution was applied at increasing doses to the substrate (1 to 56g/kg). The fermentation substrate consisted on a mixture of alfalfa hay, soybean meal, and wheat grain mixture in dry matter. After 24h of fermentation, seven new compounds were observed in the medium in amounts that correlated to the propolis dose. The dose of propolis extract linearly decreased the pH of the medium and linearly increased propionate production, which reduced the acetate-to-propionate ratio and influenced the total production of short-chain fatty acids. Propolis also linearly reduced methane production and increased the carbon dioxide-to-methane ratio. Ammonia nitrogen levels and in vitro digestibility of organic matter were similar among the treatments. The combination of increased propionate production and decreased methane production suggests better energy utilization from the feed.

High salinity in molasses wastewaters shifts anaerobic digestion to carboxylate production

Biorefinery wastewaters are often treated by means of anaerobic digestion to produce biogas. Alternatively, these wastewaters can be fermented, leading to the formation of carboxylates. Here, we investigated how lab-scale upflow anaerobic sludge blanket reactors could be shifted to fermentation by changing organic loading rate, hydraulic retention time, pH, and salinity. A strong increase in volatile fatty acid concentration up to 40 g COD L−1 was achieved through increasing salinity above 30 mS cm−1, as well as a decrease in methane production by more than 90%, which could not be obtained by adjusting the other parameters, thus, indicating a clear shift from methane to carboxylate production. Microbial community analysis revealed a shift in bacterial community to lower evenness and richness values, following the increased salinity and VFA concentration during the fermentation process. A selective enrichment of the hydrogenotrophic Methanomicrobiales took place upon the shift to fermentation, despite a severe decrease in methane production. Particle size distribution revealed a strong degranulation of the sludge in the reactor, related to the high salinity, which resulted in a wash-out of the biomass. This research shows that salinity is a key parameter enabling a shift from methane to carboxylate production in a stable fermentation process.

Effects of Medicinal Herb Extracts on In vitro Ruminal Methanogenesis, Microbe Diversity and Fermentation System.

This study was aimed to evaluate the in vitro effects of medicinal herb extracts (MHEs) on ruminal fermentation characteristics and the inhibition of protozoa to reduce methane production in the rumen. A fistulated Hanwoo was used as a donor of rumen fluid. The MHEs (T1, Veratrum patulum; T2, Iris ensata var. spontanea; T3, Arisaema ringens; T4, Carduus crispus; T5, Pueraria thunbergiana) were added to the in vitro fermentation bottles containing the rumen fluid and medium. Total volatile fatty acid (tVFA), total gas production, gas profiles, and the ruminal microbe communities were measured. The tVFA concentration was increased or decreased as compared to the control, and there was a significant (p<0.05) difference after 24 h incubation. pH and ruminal disappearance of dry matter did not show significant difference. As the in vitro ruminal fermentation progressed, total gas production in added MHEs was increased, while the methane production was decreased compared to the control. In particular, Arisaema ringens extract led to decrease methane production by more than 43%. In addition, the result of real-time polymerase chain reaction indicted that the protozoa population in all added MHEs decreased more than that of the control. In conclusion, the results of this study indicated that MHEs could have properties that decrease ruminal methanogenesis by inhibiting protozoa species and might be promising feed additives for ruminants.

Quantification of organic acids in ruminal in vitro batch culture fermentation supplemented with fumarate using a herb mix as a substrate

Two 24 h in vitro batch culture experiments were conducted to investigate the effects of fumarate addition (10 mmol L−1) on the ruminal fermentation parameters of selected medicinal herbs, and the effects of different doses of fumarate (0, 10, or 30 mmol L−1) on ruminal metabolism of organic acids when a high-concentrate diet (meadow hay and barley grain, 400/600, w/w) was supplemented with a mix of medicinal herbs (Artemisia absinthium L., Melissa officinalis L., Malva sylvestris L., Matricaria chamomilla L., Plantago lanceolata L., Foeniculum vulgare Mill., and Althaea officinalis L.). Depending on the concentration, fumarate treatment decreased methane production (by 10–11%) and increased propionate proportions (by 5–13%) with high-concentrate diets. The organic acid (fumaric, succinic, malic, and lactic acid) concentrations in the batch culture were measured at intervals of 0, 4, 6, 12, and 24 h. The time and organic acid concentrations with 10 mmol L−1 fumarate were well correlated (R 2 = 0.846). The amount of succinate was accumulated and metabolized more slowly than that of fumarate (&gt;24 h). The addition of fumarate and a herb mix could positively influence in vitro ruminal fermentation parameters of high-concentrate diets by increasing the levels of propionate and succinate as well as the pH, and by decreasing of methane emissions.

Finding cost-effective nutrient solutions and evaluating environmental conditions for biogasifying bituminous coal to methane ex situ

Biostimulation through providing nutrients to microorganisms has been proven to be highly effective in enhancing methane yield from bituminous coals in the Illinois basin. In light of the extremely cheap natural gas price at present, it is critically important to decrease the cost of nutrient solutions used to stimulate microbial gasification of coal and improve the cost-effectiveness of the biostimulation approach. To lower cost of a nutrient solution reported in previous studies, the three most expensive components, yeast extract, peptone and mercaptoethanesulfonic acid (Coenzyme M, CoM) were evaluated. Regarding the first two, decreasing their concentrations resulted in decreased methane production. In terms of CoM, its concentration could be reduced to at least half without affecting methane yield negatively. Complete elimination of CoM led to a methane yield of 85% of those with the presence of this compound in the original medium. Two complex media, trypticase soy broth (TSB) and corn steep liquor (CSL) were intended to replace yeast extract and peptone. TSB had increasingly positive effect with increasing its concentration while CSL had opposite trend. TSB at 100% (v/v) was then investigated under different cultivation conditions. Among the four parameters tested, TSB concentration and agitation were found to exert positive effect while coal loading and temperature had negative impact on methane production. The highest methane yield of 828.9ft3/ton in 30days was obtained under temperature of 28°C with a coal loading of 200g/L and agitation at 100rpm. This yield is four-time higher than those observed with the original medium. These results clearly demonstrated that biostimulation is a viable method for enhancing methane production from coal and the ingredients of nutrient solutions need to be evaluated in detail in order to make biostimulation cost-effectively at commercial scales.

Relationships between ruminal Gram-positive bacteria and methane from lactating dairy cows supplemented with monensin and tallow, alone or in combination

The aim of this study was to explore the relationships between a Gram-positive bacterial population and methane production in the rumen of dairy cows supplemented with monensin and tallow, alone or in combination. Under each treatment condition, the following ruminal fermentation parameters were measured: pH, oxidation-reduction potential (ORP), VFA, and methane production. Quantification of Gram-positive bacteria present in the rumen was performed by amplifying the 16S rDNA gene using PCR. Diversity analysis of Gram-positive bacteria was performed by PCR–denaturing gradient gel electrophoresis (DGGE), and bacterial taxonomy data were obtained by bioinformatics tools. Neither additive affected the pH or ORP, but they both reduced the total quantity of VFA. Supplementation with monensin, tallow, or their combination caused a decrease in methane production compared to the control diet. The best treatment to reduce methane production was monensin, with a reduction of 7.2% compared to the control diet. Supplementation with monensin or tallow did not affect the bacterial population. The Shannon diversity index was higher with monensin supplementation than with the other treatments. The analysis of each DGGE microbial community by the unweighted pair group method with averaging (UPGMA) revealed two clusters, one group with the control and monensin diets and the other with the tallow and combination diets. Taxonomic analysis of the dominant bands from the DGGE gel with the use of the Ribosomal Database Project (RBP) revealed that the Ruminococcaceae family was predominant, followed by the Lachnospiraceae family. Correspondence analysis (CA) suggested that both were negatively correlated with methane production in all treatments.

In vitro methane and gas production characteristics of Eragrostis trichopophora substrate supplemented with different browse foliage

An in vitro gas production study was conducted to evaluate the potential of six browse species (high, medium and low condensed tannin concentrations) collected from the Kalahari Desert as antimethanogenic additives to an Eragrostis trichopophora-based substrate. The browse species studied were Acacia luederitzii, Monechma incanum, Acacia erioloba, Acacia haematoxylon, Olea europaea and Acacia mellifera. The edible forage dry matter of the browse species were incubated with Eragrostis trichopophora in a 30 : 70 (w/w) ratio by adding 40 mL of a buffered rumen fluid at 39°C for 48 h. Gas and methane production at different time intervals after incubation were determined whereas the volatile fatty acids concentration was evaluated after 48 h. Acacia luederitzii and M. incanum foliage decreased methane production by more than 50%, but simultaneously decreased digestibility, and rumen fermentation parameters such as volatile fatty acids concentration. Tannin extracts from A. luederitzii could possibly be used as a dietary alternative to reduce methane production; however, there is a need to determine an optimum level of inclusion that may not compromise the efficiency of rumen fermentation and overall digestibility of the diet.

Factors affecting mitigation of methane emission from ruminants: Microbiology and biotechnology strategies

Climate change is a subject of global environmental concern. Increased anthropogenic Greenhouse Gas (GHG) emissions have increased the global temperature the last 100 to 200 years. Carbon dioxide and methane are the main greenhouse gases related to animal nutrition and methane has greater global warming potential than carbon dioxide. Among greenhouse gases, methane is considered a potent greenhouse gas with 21 times more global warming potential than carbon dioxide. Worldwide, ruminant livestock produce about 80 million metric tons of methane each year, accounting for about 28% of global emissions from human related activities. Therefore it is impelling animal scientists to finding solutions to mitigate methane emission from ruminants. It seems that solutions can be discussed in four topics including: nutrition (feeding), biotechnology, microbiology and management strategies. We have already published the first and second review articles on feeding strategies and management strategies. In the current review, Microbiology and biotechnology such as emphasizing on animal breeding, genetic merit, bovine somatotropin (BST), unproductive animals, vaccination, immunisation and biological control (bacteriophage, acetogenesis reductive), chemical defaunation that can be leads to decreasing methane production from ruminant animal production are discussed.

In-vitro screening of Kalahari browse species for rumen methane mitigation

The nutritional value of browse foliage from the Thorny Kalahari Dune Bush veld of South Africa is not characterized. Most of this browse species is rich in tannin, but still palatable, and is consumed by ruminants during the dry season, as well as having a role to play in mitigating enteric methane emission from ruminants. In this study, the rumen methane mitigation potential of 19 browse species foliage collected from the Thorny Kalahari Dune Bush veld, was analyzed in terms of chemical composition, in vitro fermentation, digestibility and methane production. In vitro gas and methane production and organic matter digestibility (IVOMD) were determined by using rumen fluid collected, strained and anaerobically prepared. A semi-automated system was used to measure gas production (GP) from each browse species by incubating 400 mg samples in a shaking incubator at 39 °C with or without inclusion of 400 mg of polyethylene glycol (PEG). Data for all the parameters collected were statistically analyzed using the SAS (9.0) general linear model (GLM) procedure, and differences between foliage species were determined using Duncan’s multiple-range test. Acacia luederitziiand Monechma incanumshowed the best potential for decreasing methane production by up to 90 % after 48 h of incubation. The secondary components (mainly tannins) of the browse species appeared to have a significant effect on volatile fatty acids (VFA), methane and gas production as judged by the comparison of samples incubated with or without PEG inclusion. The substantial amount of crude protein (CP) content coupled with their anti-methanogenic effect during fermentation would make these browses a potential mitigation option for small scale farmers and pastoralists in sub-Sahara Africa. However, it is also very important that systematic and strategic supplementation in a mixed diet should be looked at as the way forward in terms of best utilization.

In vitro Screening of Essential Oil Active Compounds for Manipulation of Rumen Fermentation and Methane Mitigation.

The objective of this study was to investigate the effects of 11 active compounds of essential oils (ACEO) on rumen fermentation characteristics and methane production. Two trials were conducted. In trial 1, ACEO (eugenol, carvacrol, citral, limonene, 1,4-cineole, p-cymene, linalool, bornyl acetate, α-pinene, and β-pinene) at a dose of 1,000 μL/L were incubated for 24 h in diluted rumen fluid with a 70:30 forage:concentrate substrate (16.2% crude protein; 36.6% neutral detergent fiber). Three fistulated Holstein cows were used as donors of rumen fluid. The reduction in methane production was observed with nine ACEO (up to 86% reduction) compared with the control (p<0.05). Among these, only limonene, 1,4-cineole, bornyl acetate, and α-pinene did not inhibit volatile fatty acid (VFA) production, and only bornyl acetate produced less methane per mol of VFA compared with the control (p<0.05). In a subsequent trial, the effects on rumen fermentation and methane production of two concentrations (500 and 2,000 μL/L) of bornyl acetate, the most promising ACEO from the first trial, were evaluated using the same in vitro incubation method that was used in the first trial. In trial 2, monensin was used as a positive control. Both doses of bornyl acetate decreased (p<0.05) methane production and did not inhibit VFA production. Positive effects of bornyl acetate on methane and VFA production were more pronounced than the effects of monensin. These results confirm the ability of bornyl acetate to decrease methane production, which may help to improve the efficiency of energy use in the rumen.

Short communication: Genetic study of methane production predicted from milk fat composition in dairy cows

Dairy cows produce enteric methane, a greenhouse gas with 25 times the global warming potential of CO2. Breeding could make a permanent, cumulative, and long-term contribution to methane reduction. Due to a lack of accurate, repeatable, individual methane measurements needed for breeding, indicators of methane production based on milk fatty acids have been proposed. The aim of the present study was to quantify the genetic variation for predicted methane yields. The milk fat composition of 1,905 first-lactation Dutch Holstein-Friesian cows was used to investigate 3 different predicted methane yields (g/kg of DMI): Methane1, Methane2, and Methane3. Methane1 was based on the milk fat proportions of C17:0anteiso, C18:1 rans-10+11, C18:1 cis-11, and C18:1 cis-13 (R2=0.73). Methane2 was based on C4:0, C18:0, C18:1 trans-10+11, and C18:1 cis-11 (R2=0.70). Methane3 was based on C4:0, C6:0, and C18:1 trans-10+11 (R2=0.63). Predicted methane yields were demonstrated to be heritable traits, with heritabilities between 0.12 and 0.44. Breeding can, thus, be used to decrease methane production predicted based on milk fatty acids.

Evaluation of feeds from tropical origin for in vitro methane production potential and rumen fermentation in vitro

Enteric methane arising due to fermentation of feeds in the rumen contributes substantially to the greenhouse gas emissions. Thus, like evaluation of chemical composition and nutritive values of feeds, methane production potential of each feed should be determined. This experiment was conducted to evaluate several feeds for methane production potential and rumen fermentation using in vitro gas production technique so that low methane producing feeds could be utilized to feed ruminants. Protein- and energy-rich concentrates (n=11), cereal and grass forages (n=11), and different straws and shrubs (n=12), which are commonly fed to ruminants in India, were collected from a number of locations. Gas production kinetics, methane production, degradability and rumen fermentation greatly varied (p&lt;0.01) among feeds depending upon the chemical composition. Methane production (mL/g of degraded organic matter) was lower (p&lt;0.01) for concentrate than forages, and straws and shrubs. Among shrubs and straws, methane production was lower (p&lt;0.01) for shrubs than straws. Methane production was correlated (p&lt;0.05) with concentrations of crude protein (CP), ether extract and non-fibrous carbohydrate (NFC) negatively, and with neutral detergent (NDF) and acid detergent fiber (ADF) positively. Potential gas production was negatively correlated (p=0.04) with ADF, but positively (p&lt;0.01) with NFC content. Rate of gas production and ammonia concentration were influenced by CP content positively (p&lt;0.05), but by NDF and ADF negatively (p&lt;0.05). Total volatile fatty acid concentration and organic matter degradability were correlated (p&lt;0.05) positively with CP and NFC content, but negatively with NDF and ADF content. The results suggest that incorporation of concentrates and shrubs replacing straws and forages in the diets of ruminants may decrease methane production.

Effects of titanium dioxide and zinc oxide nanoparticles on methane production from anaerobic co-digestion of primary and excess sludge

Anaerobic co-digestion of primary and excess sludge is regarded as an efficient way to reuse sludge organic matter to produce methane. In this study, short-term and long-term exposure experiments were conducted to investigate the possible effects of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles (NPs) on methane production from anaerobic co-digestion of primary and excess sludge. The data showed that TiO2 NPs had no measurable impact on methane production, even at a high concentration (150 mg/g total suspended solids (TSS)). However, short-term (8 days) exposure to 30 or 150 mg/g-TSS of ZnO NPs significantly decreased methane production. More importantly, these negative effects of ZnO NPs on anaerobic sludge co-digestion were not alleviated by increasing the adaptation time to 105 days. Further studies indicated that the presence of ZnO NPs substantially decreased the abundance of methanogenic archaea, which reduced methane production. Meanwhile, the activities of some key enzymes involved in methane production, such as protease, acetate kinase, and coenzyme F420, were remarkably inhibited by the presence of ZnO NPs, which was also an important reason for the decreased methane production. These results provide a better understanding of the potential risks of TiO2 and ZnO NPs to methane production from anaerobic sludge co-digestion.

The Effect of Feeding Horses a High Fiber Diet With or Without Exogenous Fibrolytic Enzymes Supplementation on Nutrient Digestion, Blood Chemistry, Fecal Coliform Count, and In Vitro Fecal Fermentation

Sixteen Quarter Horse mares (450 to 500-kg body weight) were used in a complete randomized design to determine the effects of feeding a high fiber diet with or without exogenous fibrolytic enzymes on nutrient digestion, blood chemistry, fecal coliform count, and in vitro fecal fermentation. The treatments comprised feeding the horses (1) a basal diet without enzyme addition (control); (2) control diet plus cellulase at 10 mL/mare/d (CELL); (3) control diet plus xylanase at 10 mL/mare/d (XYL); or (4) control diet plus a mixture of 5 mL cellulase and 5 mL xylanase/mare/d (CX). The basal concentrate diet consisted of a mixture of 50% commercial concentrate and 50% wheat bran fed at 4 kg/horse, offered twice daily at 04:00 and 16:00 hours, and oat straw offered ad libitum at 05:00 and 17:00 hours. The enzyme allocation for each day was mixed with 1 kg of concentrate diet at 04:00 hours, and the experiment lasted for 15 days comprising 10 days of adaptation and 5 days for sample collection. The in vitro cecal fermentation with addition of 2 μL/g dry matter (DM) of each enzyme (CELL, XYL, and CX) to a basal diet of oat straw and concentrates mixture (1:1 DM) as a substrate was carried out. The mares fed enzyme-supplemented diets had greater (P < .01) oat straw and total nutrients intakes compared with the control diet. Feeding enzyme-supplemented diets increased total nutrients digestibility (P < .05) and blood total protein (P = .0277) compared with the control. Feeding XYL-supplemented diet increased blood alanine transaminase and aspartate aminotransferase concentrations (P < .05) compared with control treatment. Lower fecal coliform count was obtained (P = .0114) with mares fed CX diet compared with control mares. The XYL and CX treatments had decreased asymptotic gas production (GP) (P = .0173) with lower rate of GP (P = .0412) compared with CELL treatment. CELL and XYL treatments had decreased (P = .0394) lag times compared with control and CX treatments. At 24 hours of incubation, CELL and XYL treatments decreased methane production (P = .0131), whereas CX treatment increased its production at 48 hours (P = .0202) compared with control treatment. No effect was observed (P > .05) with enzymes addition on carbon dioxide production at different hours of incubation compared with control treatment. Higher in vitro DM degradability values (P = .0092) were obtained with the enzyme treatments compared with control treatment. Fermentation pH was lower (P = .0396) with CX treatment and increased with CELL treatment compared with the control and XYL, showing a greater pH with CELL than the other treatments. It can be concluded that addition of fibrolytic enzymes at 10 mL/mare/d improved feed intake and nutrients digestibility without affecting mare's health.

Evaluation of several tropical tree leaves for methane production potential, degradability and rumen fermentation in vitro

The objective of this study was to investigate 18 tree leaves for methane production potential, degradability and rumen fermentation characteristics in vitro. The higher concentrations (P<0.01) of total phenolics were noted in Prosopis cineraria (99.7gkg−1), Acacia tortilis (89.4gkg−1) and Psidium guajava (89.3gkg−1), non-tannin phenolics in A. tortilis (36.6gkg−1) followed by Syzygium cumini (26.0gkg−1), total tannins in P. cineraria (82.1gkg−1) and P. guajava (74.3gkg−1), and condensed tannins in A. tortilis (47.2gkg−1), P. guajava (46.6g kg−1) and P. cineraria (43.2gkg−1). Among the 18 leaves, methane production expressed as mlg−1 degradable organic matter (OM) was lower (P<0.01) for Acacia nilotica (12.6ml), P. cineraria (12.9ml), Ficus religiosa (13.9ml), S. cumini (13.8ml) and Azadirachta indica (13.7ml) than other tree leaves. Total volatile fatty acid (VFA) concentration was greater (P<0.01) for Tamarindus indica, followed by Acacia nilotica and lowest for S. cumini. Degradability of dry matter (DM) was higher (P<0.01) for Moringa oleifera, Acacia senegal, Acacia excelsa, Morus alba, A. indica and F. religiosa (77–83%), and lowest for Bambusa sp. (45%) and Ficus benghalensis (52%). Microbial biomass production was lowest for Bambusa sp. leaves and higher (P<0.01) for S. cumini, A. tortilis, A. nilotica, P. guajava than other leaves. Overall, the leaves of S. cumini, A. indica, F. religiosa and A. nilotica not only produced less methane per unit of degradable OM, but also had generally greater OM degradability and favored production of microbial biomass compared with other leaves. These leaves could be explored for decreasing methane production in small ruminant production systems of tropical developing countries.

Response of the rumen archaeal and bacterial populations to anti-methanogenic organosulphur compounds in continuous-culture fermenters.

Study of the efficacy of methanogenesis inhibitors in the rumen has given inconsistent results, mainly due to poorly understood effects on the key microbial groups involved in pathways for methane (CH4) synthesis. The experiment described in this report was designed to assess the effect of propyl propane thiosulfinate (PTS), diallyl disulfide (DDS) and bromochloromethane (BCM) on rumen fermentation, methane production and microbial populations in continuous culture fermenters. No effects on total volatile fatty acids (VFA) were observed with PTS or DDS, but VFA were decreased with BCM. Amylase activity increased with BCM as compared with the other treatments. A decrease in methane production was observed with PTS (48%) and BCM (94%) as compared with control values. The concentration of methanogenic archaea decreased with BCM from day 4 onward and with PTS on days 4 and 8. Pyrosequencing analysis revealed that PTS and BCM decreased the relative abundance of Methanomicrobiales and increased that of Methanobrevibacter and Methanosphaera. The total concentration of bacteria was not modified by any treatment, although treatment with BCM increased the relative abundance of Prevotella and decreased that of Ruminococcus. These results suggest that the inhibition of methane production in the rumen by PTS and BCM is associated with a shift in archaeal biodiversity and changes in the bacterial community with BCM.

Effect of combined herbal feed additives on methane, total gas production and rumen fermentation.

The present study was to evaluate effect of herbal feed additives on methane and total gas production during the rumen fermentation for environment and animal health concern. Different parts of the five medicinal plants were selected such as leaf and small stems of Ocimum sanctum (Tulsi), roots of Curcuma longa (Haldi), fruits of Emblica officinalis (Amla), leaves of Azadirachta indica (Neem) and leaves and small stem of Clerodendrum phlomidis (Arni) for our study. Addition of different herbal additive combinations did not influence IVDMD and total gas production however methane production (mg/g of substrate DM) was significantly (P<0.05) reduced in Amla: Neem and Neem: Arni combinations. Total nitrogen significantly (P<0.01) increased in the combinations of Tulsi: Haldi and Amla: Neem. TCA–ppt-N is significantly (P<0.01) increased in Tulsi: Haldi, Haldi: Amla, Amla: Neem and Neem: Arni however NH3-N (mg/dl) significantly decreased in all treatments. We conclude that the screening of plant combinations, Amla: Neem and Neem: Arni have potential to decrease methane production and our herbal feed supplements have no side-effects on the ruminant in small amount.

Effects of garlic oil, nitrate, saponin and their combinations supplemented to different substrates on in vitro fermentation, ruminal methanogenesis, and abundance and diversity of microbial populations.

To investigate the effect of garlic oil (G), nitrate (N), saponin (S) and their combinations supplemented to different forage to concentrate substrates on methanogenesis, fermentation, diversity and abundances of bacteria and Archaea in vitro. The study was conducted in an 8 × 2 factorial design with eight treatments and two substrates using mixed ruminal batch cultures obtained. Quillaja S (0·6 g l(-1) ), N (5 mmol l(-1) ) and G (0·27 g l(-1) ) were used separately or in binary and tertiary combinations. The two substrates contained grass hay and a dairy concentrate mixture at a 70 : 30 (high-forage substrate) ratio or a 30 : 70 (high-concentrate substrate) ratio. Ruminal fermentation and cellulolytic bacterial populations were affected by interaction between substrate and anti-methanogenic compounds. The inhibitor combinations decreased the methane production additively regardless of substrate. For the high-concentrate substrate, S decreased methane production to a greater extent, so did G and N individually for the high-forage substrate. Feed degradability and total volatile fatty acid (VFA) concentrations were not decreased by any of the treatments. Fibre degradability was actually improved by N+S for the high-forage substrate. VFA concentrations and profiles were affected differently by different anti-methanogenic inhibitors and their combinations. All treatments inhibited the growth of Archaea, but the effect on Fibrobacter succinogenes, Ruminococcus albus and Ruminococcus flavefaciens varied. The results suggest that substrate influences the efficacy of these inhibitors when they are used separately, but in combinations, they can lower methanogenesis additively without much influence from the substrate. The presented research provided evidence that binary and tertiary combination of garlic oil, nitrate and saponin can lower the methane production additively without adversely impacting rumen fermentation and degradability, and forage to concentrate ratio does not change the above effects. These anti-methanogenic inhibitors in combination may have practical application to mitigate methane emission from ruminants.

Redundancy, resilience, and host specificity of the ruminal microbiota: implications for engineering improved ruminal fermentations

The ruminal microbial community is remarkably diverse, containing 100s of different bacterial and archaeal species, plus many species of fungi and protozoa. Molecular studies have identified a “core microbiome” dominated by phyla Firmicutes and Bacteroidetes, but also containing many other taxa. The rumen provides an ideal laboratory for studies on microbial ecology and the demonstration of ecological principles. In particular, the microbial community demonstrates both redundancy (overlap of function among multiple species) and resilience (resistance to, and capacity to recover from, perturbation). These twin properties provide remarkable stability that maintains digestive function for the host across a range of feeding and management conditions, but they also provide a challenge to engineering the rumen for improved function (e.g., improved fiber utilization or decreased methane production). Direct ruminal dosing or feeding of probiotic strains often fails to establish the added strains, due to intensive competition and amensalism from the indigenous residents that are well-adapted to the historical conditions within each rumen. Known exceptions include introduced strains that can fill otherwise unoccupied niches, as in the case of specialist bacteria that degrade phytotoxins such as mimosine or fluoroacetate. An additional complicating factor in manipulating the ruminal fermentation is the individuality or host specificity of the microbiota, in which individual animals contain a particular community whose species composition is capable of reconstituting itself, even following a near-total exchange of ruminal contents from another herd mate maintained on the same diet. Elucidation of the interactions between the microbial community and the individual host that establish and maintain this specificity may provide insights into why individual hosts vary in production metrics (e.g., feed efficiency or milk fat synthesis), and how to improve herd performance.

Rumen fermentation pattern, lipid metabolism and the microbial community of sheep fed a high-concentrate diet supplemented with a mix of medicinal plants

The aim of this study was to determine the effects of a medicinal plant mixture (MP), sunflower oil (SO) and a combination of the medicinal plant mixture and sunflower oil (MPSO) on fermentation end products, the fatty acid composition of the rumen fluid, the ruminal microbial population as well as antioxidant status in the blood of sheep fed a high-concentrate diet. Four rumen-fistulated rams were randomly assigned according to a 4×4 Latin square design and fed a basal diet consisting of 720g DM/day meadow hay and 540g DM/day barley grain. The basal diet was supplemented with no additive (control), a medicinal plant mixture (MP, 10% replacement of meadow hay; 72g DM/day), sunflower oil (SO, 36g/day) and the combination (MPSO). Before the in vivo experiment, 24h ruminal incubations in vitro were performed (meadow hay/barley grain; 400/600, w/w; MP; 10% replacement of meadow hay; SO; 3.5% DM; MPSO). The in vitro experiment with MP and MPSO increased the in vitro dry matter digestibility (P<0.001) and decreased methane production (P=0.021), while the MPSO treatment increased the concentration of polyunsaturated fatty acids (PUFA; P<0.001). In sheep, the rumen characteristics were not affected by the treatments. No treatment effect on the rumen eubacterial population was detected by the 16S-polymerase chain reaction-denaturizing gradient gel electrophoresis method. The beneficial effects of MP and MPSO on PUFA concentration observed in vitro were not fully confirmed in vivo. However, these results could point to the promising effects of using a medicinal plant mixture in high-concentrate diets of ruminants without adverse effects on the fermentation characteristics and microbial ecosystem in sheep rumen.