In vitro screening of the potential of numerous plant species as antimethanogenic feed additives for ruminants

The roles of phytogenic feed additives, trees, shrubs, and forages on mitigating ruminant methane emission

Ruminant animals naturally emit methane gas owing to anaerobic microbial fermentation in the rumen, and these gases are considered major contributors to global warming. Scientists worldwide are attempting to minimize methane emissions from ruminant animals. Some of these attempts include the manipulation of rumen microbes using antibiotics, synthetic chemicals, dietary interventions, probiotics, propionate enhancers, stimulation of acetogens, manipulation of rumination time, vaccination, and genetic selection of animals that produce low methane (CH4). The majority of synthetic additives are harmful to both beneficial rumen microbes and the host or only temporarily affect methanogenesis. Phytogenic feed additives (PFAs) have recently emerged as the best alternatives to antibiotics and synthetic chemicals because of growing public concerns regarding drug resistance and the negative impacts of antibiotics and synthetic chemicals on humans, livestock, and the environment. These additives reduce methane production and improve the volatile fatty acid profile. In this review, we provide an overview of PFA sources and how their bioactive components affect the rumen microbiome to reduce methane emissions. Additionally, we highlight the mechanisms of action of PFAs as a whole, as well as some of their bioactive components. We also review some selected trees, herbs, shrubs, and forages and their roles in reducing methane emissions.

Development and application of a multi-step porcine in vitro system to evaluate feedstuffs and feed additives for their efficacy in nutrient digestion, digesta characteristics, and intestinal immune responses

In vitro model provides alternatives to the use of live animals in research. In pig nutrition, there has been a tremendous increase in in vivo research over the decades. Proper utilization of in vitro models could provide a screening tool to reduce the needs of in vivo studies, research duration, cost, and the use of animals and feeds. This study aimed to develop a multi-step porcine in vitro system to simulate nutrient digestion and intestinal epithelial immune responses affected by feedstuffs and feed additives. Seven feedstuffs (corn, corn distillers dried grains with solubles [corn DDGS], barley, wheat, soybean meal, soy protein concentrates, and Corynebacterium glutamicum cell mass [CGCM]), feed enzymes (xylanase and phytase), and supplemental amino acids (arginine, methionine, and tryptophan), were used in this in vitro evaluation for their efficacy on digestibility, digesta characteristics, and intestinal health compared with the results from previously published in vivo studies. All in vitro evaluations were triplicated. Data were analyzed using Mixed procedure of SAS9.4. Evaluations included (1) nutrient digestibility of feedstuffs, (2) the effects of feed enzymes, xylanase and phytase, on digestibility of feedstuffs and specific substrates, and (3) the effects of amino acids, arginine, tryptophan, and methionine, on anti-inflammatory, anti-oxidative, and anti-heat stress statuses showing their effects (P < 0.05) on the measured items. Differences in dry matter and crude protein digestibility among the feedstuffs as well as effects of xylanase and phytase were detected (P < 0.05), including xylo-oligosaccharide profiles and phosphorus release from phytate. Supplementation of arginine, tryptophan, and methionine modulated (P < 0.05) cellular inflammatory and oxidative stress responses. The use of this in vitro model allowed the use of 3 experimental replications providing sufficient statistical power at P < 0.05. This indicates in vitro models can have increased precision and consistency compared with in vivo animal studies.

Effect of hydroxypropyl methylcellulose (HPMC) hard capsules on in vitro rumen fermentation kinetics of commonly used feeds in ruminant feeding

BACKGROUND

Accurate dosing of feed additives is often required to evaluate their effects on rumen fermentation. This can be done using soluble but nonfermentable hydroxypropyl methylcellulose (HPMC) hard capsules.

OBJECTIVES

The aim of the study was to evaluate the effect of HPMC hard capsules on the extent and rate of in vitro gas production in eleven feeds.

METHODS

Six high-fibre feeds and five concentrates, were weighed into syringes either directly or into HPMC capsules and incubated anaerobically in 30 mL buffered rumen fluid at 39°C. Data obtained from gas production measurements were fitted using the Gompertz model to obtain kinetic parameters for gas production.

RESULTS

HPMC hard capsules had no effect on the gas production of the blank sample and concentrate feeds. In contrast, high-fibre feeds weighed in HPMC showed a significant decrease (p < 0.05) in total gas production and gas produced within 24 h of incubation.

CONCLUSIONS

The use of HPMC hard capsules was found to be inappropriate for determining gas production kinetics because fermentation subsides at a certain point when peak fermentation is reached (at TMFR), resulting in a decrease in both total potential gas production and gas production within 24 h of incubation. This is particularly evident when high-fibre feeds are incubated.

Supplementation of complex natural feed additive containing (C. militaris, probiotics and red ginseng by-product) on rumen-fermentation, growth performance and carcass characteristics in Korean native steers

This study evaluated the effects of a complex natural feed additive on rumen fermentation, carcass characteristics and growth performance in Korean-native steers. In this study, in vitro and in vivo experiment were conducted. Seven different levels of complex natural feed additive (CA) were added to the buffered rumen fluid using AnkomRF gas production system for 12, 24 and 48 h. All experimental data were analyzed by mixed procedure of SAS. Total gas production increased in the CA groups, with the highest response observed in the 0.06% group at 48 h of incubation (linear, p = 0.02; quadratic, p < 0.01). Regarding rumen fermentation parameters, the total volatile fatty acid (TVFA) tended to increase in all the CA groups (p = 0.07). The concentrations of butyrate, iso-butyrate, and iso-valerate significantly increased in all treatment groups (p < 0.05). In the in vivo experiment, 23 Korean-native steers were allocated to two groups: (1) Control and (2) Treatment; control +0.07% CA (DM basis), in a randomized complete-block design and blocked by body weight (ave. body weight = 641.96 kg ± 62.51 kg, p = 0.80) and feed intake (ave. feed intake = 13.96 kg ± 0.74 kg, p = 0.08) lasted for 252 days. Average daily gain decreased in the treatment group (p < 0.01). Backfat thickness significantly decreased in the CA group (p = 0.03), whereas meat color tended to increase (p = 0.07). In conclusion, in the in vitro experiment, the inclusion of complex natural feed additive decreased methane proportion and tended to increase TVFA production, but supplementation to Korean native steers decreased average daily gain and backfat thickness.

Anti-nutrient contents and methane reduction potential of medicinal plants from maize stover based diet

Greenhouse gas emissions from Ethiopian agriculture are significantly increasing, with the largest share is from enteric fermentation and manure left on pasture. An investigation was conducted to evaluate the anti-nutrient composition and effect of commonly used medicinal plant extracts on enteric methane emission from fibrous feeds using maize stover as substrate feed. Total phenols, flavonoid, tannin and essential oil contents were analyzed using established standards. Effects of leaf extracts of Acacia nilotica, Azadirachta indica, three varieties of Cymbopogon citratus (Cymbopogon citratus-I, Cymbopogon citratus java and Cymbopogon citratus upper awash), Leucaena leucocephala, Moringa stenopetala, three varieties of Rosmarinus officinalis (Rosmarinus officinalis I, Rosmarinus officinalis II and Rosmarinus officinalis III) and Thyme schimperi, seed of three Coriandrum sativum varieties (Coriandrum sativum Batu, Coriandrum sativum Tulu and Coriandrum sativum Waltai) and root of Echinops kebericho on total gas production, digestibility and methane production of maize stover were investigated at different doses using the standard procedures. The results indicated that leaf extracts of Acacia nilotica had the highest (P < 0.001) total phenolic and total tannin contents. Compared to other evaluated plant species, all varieties of Cymbopogon citratus had the highest (P < 0.001) flavonoid content. Significantly high (P < 0.001) essential oil content was observed in Rosmarinus officinalis II than other varieties of Rosmarinus officinalis and other plant species. Significant reduction (P < 0.001) of methane production was observed with extracts of Cymbopoon citratus java (22.5 % less methane than the control) and thyme schimperi (16.7 % less methane than the control) at dose of 50 mg/kg DM. There was also significant (P < 0.001) interaction effect between plant species and dose rates at 50 mg/kg DM for both plant species. It can be concluded that the use of 50 mg/kg DM of Cymbopoon citratus java and Thyme schimperi extract to maize stover reduced methane production without negatively affecting feed digestibility. Further studies are necessary to examine the storability of the extracts in different time durations and evaluate their effects in vivo with animals.

Methane reduction by quercetin, tannic and salicylic acids: influence of molecular structures on methane formation and fermentation in vitro

Plant secondary metabolites (PSMs) can potentially reduce ruminal methane formation. However, related to differences in their molecular structures, it is not yet clear what causes an anti-methanogenic effect. In an in vitro system simulating rumen fermentation, we investigated the impact of eight compounds with distinct chemical characteristics (gallic and salicylic acids, tannic acid, catechin, epicatechin, quercetin, rutin, and salicin) when added to a basal feed (maize silage) at a concentration of 12% of the feed dry matter. After 48 h of incubation in buffered rumen fluid, methane production was significantly lowered by quercetin (43%), tannic acid (39%) and salicylic acid (34%) compared to the control (maize silage alone) and without changes in total volatile fatty acid production during fermentation. No other PSM reduced methane formation as compared to control but induced significant differences on total volatile fatty acid production. The observed differences were related to lipophilicity, the presence of double bond and carbonyl group, sugar moieties, and polymerization of the compounds. Our results indicate the importance of distinct molecular structures of PSMs and chemical characteristics for methane lowering properties and volatile fatty acid formation. Further systematic screening studies to establish the structure-function relationship between PSMs and methane reduction are warranted.

Effects of Polymeric Media-Coated Gynosaponin on Microbial Abundance, Rumen Fermentation Properties and Methanogenesis in Xinjiang Goats

Gynosaponin is known to modulate rumen methanogenesis and microbial fermentation characteristics in ruminants. The current experiment aimed to determine the time-dependent effects of intraruminal polymeric media-coated gynosaponin (PMCG) supplementation on the methanogenesis, rumen fermentation properties and microbial abundance in Xinjiang goats. Eight goats were used in a 2 × 2 crossover arrangement with a PMCG group (8 g/kg DMI) and a control group (0 g/kg DMI). The experiment was divided into four phases, each lasted 21 d. Ruminal contents were obtained for analysis of rumen fermentation properties and microbial abundance. Protozoa numbers were counted by microscope and the abundance of methanogens, rumen fungi and cellulolytic bacteria were quantified by real-time PCR. The results indicated that PMCG significantly reduced methane production (p < 0.05) during the first two phases but this increased to baseline again during the last two phases. Meanwhile, the concentration of acetate decreased remarkably, which resulted in a significant reduction in the acetate to propionate ratio and total VFA concentration (p < 0.05). However, other rumen properties and dry matter intake were not affected (p > 0.05). During the first and second phases, the protozoa numbers and gene copies of methanogens, total bacteria and F. succinogens relative to the 16 s rDNA were all slightly decreased, but the statistical results were not significant. However, the ruminal supplementation of PMCG had little effect on other tested microbes. Accordingly, it was concluded that the addition of PMCG had an inhibitory effect on methane production probably due to a decline in methanogen numbers.

Chemical, mineral composition, in vitro ruminal fermentation and buffering capacity of some rangeland-medicinal plants

A diverse group of rangeland-medicinal plants are being used by ruminant whilst some of them have not been assessed for their nutritional value. This study was aimed to evaluate the chemical and mineral composition, buffering capacity, and in vitro fermentation of some rangeland-medicinal plants including Thymus kotschyanus, Ziziphora persica, Lallemantia royleana, and Scutellaria litwinowii in the family Lamiaceae, and Hypericum scabrum, in the family Hypericaceae. The results indicated that crude protein (CP) content ranged from 8.66% (S. litwinowii) to 12.17% of DM (H. scabrum). It was found that Z. persica had the highest potential gas production, metabolism energy (ME), relative feed value (RFV), and dry matter digestibility (DMD) values of 53.44 (mL 200-1 mg DM), 5.84 (MJ kg-1 DM), 170.66 and 70.88%, respectively. Mineral content differed among plants; Ca ranged from 5.79 to 41.96 g kg-1 DM. The concentrations of Ca, K, Mg, Fe, Zn, and Co were highest for L. royleana. Total volatile fatty acids (TVFA) and propionate concentrations were highest in the culture medium cultured with Z. persica, however, acetate, and butyrate were highest in H. scabrum. Acid-base buffering capacity was lower in T. kotschyanus and H. scabrum compared to other plants, while it was higher in S. litwinowii. Overall, it can be concluded that among plants evaluated in this study, Z. persica had higher nutritional value for sheep feeding.

UHPLC-ESI-QqTOF Analysis and In Vitro Rumen Fermentation for Exploiting Fagus sylvatica Leaf in Ruminant Diet

In recent years, animal husbandry has aimed at improving the conditions of livestock animals useful for humans to solve environmental and health problems. The formulation of animal feeds or supplements based on antioxidant plant compounds is considered a valuable approach and an alternative for livestock productivity. Forest biomass materials are an underestimated source of polyphenolic compounds whose sustainable recovery could provide direct benefits to animals and, indirectly, human nutrition. In this context, an alcohol extract from leaves of Fagus sylvatica L. was first investigated through an untargeted ultra-high-performance liquid chromatography-high-resolution tandem mass spectrometry (UHPLC-HRMS/MS) approach. Then, it was fractionated into a fatty acid-rich and a polyphenolic fraction, as evidenced by total lipid, phenol, and flavonoid content assays, with antiradical and reducing activity positively correlated to the latter. When tested in vitro with rumen liquor to evaluate changes in the fermentative parameters, a significant detrimental effect was exerted by the lipid-rich fraction, whereas the flavonoid-rich one positively modulated the production of volatile fatty acids (i.e., acetate, butyrate, propionate, etc.).

Changes in the concentration of methane in the ecosystem in vitro against the background of Asteraceae family plants biomass

The assessment of Asteráceae Family Plants (rhizomes and roots of elecampane and wormwood) influence on the process of methane formation in the rumen ecosystem and metabolic processes was carried out. Studies (in vitro) were carried out using ANKOM Daisy II incubator (modifications D200 and D200I) according to a specialized method. Rumen contents were obtained from beef bulls with chronic rumen fistula. Gas analysis of air and volatile fatty acids samples was performed by gas chromatography. The results of the study showed that different dosages of phytobiotic preparations did not significantly affect the characteristics of fermentation in vitro. Phytobiotic preparations of elecampane and wormwood reduce the production of methane in the ruminal fluid, which may be associated with various active components or dosages of their administration.

Untargeted Metabolomics Combined with Solid Phase Fractionation for Systematic Characterization of Bioactive Compounds in Hemp with Methane Mitigation Potential

This study systematically evaluates the presence of methane mitigating metabolites in two hemp (Cannabis sativa L.) varieties, Futura 75 and Finola. Hemp metabolites were extracted with methanol and fractionated using Solid Phase Extraction (SPE). Extracts, fractions, and the remaining pulp were screened for their methane mitigating potential using an in vitro model of rumen fermentation. The bioactive metabolites were identified with Liquid Chromatography-Mass Spectrometry (LC-MS). When incubated with a standard feed (maize silage), the extract of Futura 75 significantly reduced methane production compared to that of control (without added extract) and without negative effects on feed degradability and volatile fatty acid patterns. The compounds responsible for the methane mitigating effect were assigned to flavonoid glycosides. However, none of the fractions of Futura 75 or the pulp exhibited similar effect on methane emission. Butyric acid concentration in the fermentation inoculum was significantly increased, which could indicate why methane production was higher, when incubated with the fractions and the pulp. The extract of Finola did not show a similar significant effect, however, there was a numerical tendency towards lower methane production. The difference in methane mitigating properties between Cannabis sativa L. Futura 75 and Finola, could be related to the content of bioactive flavonoids.

Boosting animal performance, immune index and antioxidant status in post-weaned bull calves through dietary augmentation of selective traditional medicinal plants

Traditional medicinal plants (TMP) are considered valuable alternatives to hazardous synthetic chemical utilized as animal growth promoters. This study aimed to evaluate effects of dietary supplementation of seed and leaf powder (75:25) of three Bangladeshi TMP viz. Emblica officinalis Gaertn., Terminalia bellirica Gaertn. Roxb., and Terminalia chebula Retz. on growth performance, digestibility of nutrients, hematological indices, immune index and antioxidant status in post-weaned bull calves. Dietary treatments: TMP1 (basal diet = green grass + concentrate), TMP2 (basal diet + 0.5% mixture of seed and leaf (75:25) of E. officinalis Gaertn.), TMP3 (basal diet + 0.5% mixture of seed and leaf (75:25) of T. bellirica Gaertn. Roxb.), and TMP4 (basal diet + 0.5% mixture of seed and leaf (75:25) of T. chebula Retz.). Supplementation of TMP significantly (p < 0.10) improved weight gain without affecting digestibility. Hematological indices did not change much by treatment of TMP except for enhancement of monocyte (p < 0.10) and platelet percentage (p < 0.05). A reduction in IGF, enhancement (p < 0.05) of lymphocyte proliferation, and IgG were recorded in TMP2, TMP3 and TMP4 compared to TMP1. Decreasing (p < 0.05) trend of interleukins-1 and 6, and an elevation of TNF-α and antioxidant status were recorded in the TMP2, TMP3, and TMP4 in comparison to TMP1. An elevated level of total antioxidant and glutathione peroxidase activities were found in calves treated with TMP2, TMP3, and TMP4 (p < 0.05) relative to TMP1. Taken together, our results indicate that supplementation of feed with Bangladeshi TMP promoted growth and some health indices like immune-advocating efficacy of post-weaned bull calves.

Sustainability of the Dairy Industry: Emissions and Mitigation Opportunities

Dairy cattle provide a major benefit to the world through upcycling human inedible feedstuffs into milk and associated dairy products. However, as beneficial as this process has become, it is not without potential negatives. Dairy cattle are a source of greenhouse gases through enteric and waste fermentation as well as excreting nitrogen emissions through their feces and urine. However, these negative impacts vary widely due to how and what these animals are fed. In addition, there are many promising opportunities for further reducing emissions through feed and waste additives. The present review aims to further expand on where the industry is today and the potential avenues for improvement. This area of research is still not complete and additional information is required to further improve our dairy systems impact on sustainable animal products.

Targeted and Untargeted Metabolic Profiling to Discover Bioactive Compounds in Seaweeds and Hemp Using Gas and Liquid Chromatography-Mass Spectrometry

Greenhouse gas emissions are a global problem facing the dairy/beef industry. Novel feed additives consisting of seaweeds and hemp containing bioactive compounds are theorized to reduce enteric methane emissions. In this study we aimed to investigate the metabolic profiles of brown, red and green seaweeds and hemp using gas chromatography and liquid chromatography mass spectrometry. We used targeted and untargeted approaches, quantifying known halomethanes and phenolics, as well as identifying potentially novel bioactive compounds with anti-methanogenic properties. The main findings were: (a) Asparagopsis taxiformis contained halomethanes, with high concentrations of bromoform (4200 µg/g DW), six volatile halocarbons were tentatively identified; (b) no halomethanes were detected in the other studied seaweeds nor in hemp; (c) high concentrations of lignans were measured in hemp; (d) a high numbers of sulfated phenolic acids and unidentified sulfuric acid-containing compounds were detected in all seaweeds; (e) flavonoid glucosides and glucuronides were mainly identified in hemp; and (f) the condensed tannin gallocatechin was tentatively identified in Fucus sp. Using the combined metabolomics approach, an overview and in-depth information on secondary metabolites were provided. Halomethanes of Asparagopsis sp. have already been shown to be anti-methanogenic; however, metabolic profiles of seaweeds such as Dictyota and Sargassum have also been shown to contain compounds that may have anti-methanogenic potential.

In Vitro Screening of East Asian Plant Extracts for Potential Use in Reducing Ruminal Methane Production

Indiscriminate use of antibiotics can result in antibiotic residues in animal products; thus, plant compounds may be better alternative sources for mitigating methane (CH₄) production. An in vitro screening experiment was conducted to evaluate the potential application of 152 dry methanolic or ethanolic extracts from 137 plant species distributed in East Asian countries as anti-methanogenic additives in ruminant feed. The experimental material consisted of 200 mg total mixed ration, 20 mg plant extract, and 30 mL diluted ruminal fluid-buffer mixture in 60 mL serum bottles that were sealed with rubber stoppers and incubated at 39 °C for 24 h. Among the tested extracts, eight extracts decreased CH₄ production by >20%, compared to the corresponding controls: stems of Vitex negundo var. incisa, stems of Amelanchier asiatica, fruit of Reynoutria sachalinensis, seeds of Tribulus terrestris, seeds of Pharbitis nil, leaves of Alnus japonica, stem and bark of Carpinus tschonoskii, and stems of Acer truncatum. A confirmation assay of the eight plant extracts at a dosage of 10 mg with four replications repeated on 3 different days revealed that the extracts decreased CH₄ concentration in the total gas (7-15%) and total CH₄ production (17-37%), compared to the control. This is the first report to identify the anti-methanogenic activities of eight potential plant extracts. All extracts decreased ammonia (NH₃-N) concentrations. Negative effects on total gas and volatile fatty acid (VFA) production were also noted for all extracts that were rich in hydrolysable tannins and total saponins or fatty acids. The underlying modes of action differed among plants: extracts from P. nil, V. negundo var. incisa, A. asiatica, and R. sachalinensis resulted in a decrease in total methanogen or the protozoan population (p < 0.05) but extracts from other plants did not. Furthermore, extracts from P. nil decreased the population of total protozoa and increased the proportion of propionate among VFAs (p < 0.05). Identifying bioactive compounds in seeds of P. nil by gas chromatography-mass spectrometry analysis revealed enrichment of linoleic acid (18:2). Overall, seeds of P. nil could be a possible alternative to ionophores or oil seeds to mitigate ruminal CH₄ production.

Impact of Zinc and/or Herbal Mixture on Ruminal Fermentation, Microbiota, and Histopathology in Lambs

We investigated the effect of diets containing organic zinc and a mixture of medicinal herbs on ruminal microbial fermentation and histopathology in lambs. Twenty-eight lambs were divided into four groups: unsupplemented animals (Control), animals supplemented with organic zinc (Zn, 70 mg Zn/kg diet), animals supplemented with a mixture of dry medicinal herbs (Herbs, 100 g dry matter (DM)/d) and animals supplemented with both zinc and herbs (Zn+Herbs). Each lamb was fed a basal diet composed of meadow hay (700 g DM/d) and barley (300 g DM/d). The herbs Fumaria officinalis L. (FO), Malva sylvestris L. (MS), Artemisia absinthium L. (AA) and Matricaria chamomilla L. (MC) were mixed in equal proportions. The lambs were slaughtered after 70 d. The ruminal contents were used to determine the parameters of fermentation in vitro and in vivo and to quantify the microbes by molecular and microscopic methods. Samples of fresh ruminal tissue were used for histopathological evaluation. Quantitative analyses of the bioactive compounds in FO, MS, AA, and MC identified 3.961, 0.654, 6.482, and 12.084 g/kg DM phenolic acids and 12.211, 6.479, 0.349, and 2.442 g/kg DM flavonoids, respectively. The alkaloid content in FO was 6.015 g/kg DM. The diets affected the levels of total gas, methane and n-butyrate in vitro (P < 0.046, < 0.001, and < 0.001, respectively). Relative quantification by real-time PCR indicated a lower total ruminal bacterial population in the lambs in the Zn and Zn+Herbs groups than the Control group (P < 0.05). The relative abundances of Ruminococcus albus, R. flavefaciens, Streptococcus bovis, and Butyrivibrio proteoclasticus shifted in the Zn group. Morphological observation found a focally mixed infiltration of inflammatory cells in the lamina propria of the rumen in the Zn+Herbs group. The effect of the organic zinc and the herbal mixture on the parameters of ruminal fermentation in vitro was not confirmed in vivo, perhaps because the ruminal microbiota of the lambs adapted to the zinc-supplemented diets. Long-term supplementation of a diet combining zinc and medicinal herbs, however, may negatively affect the health of the ruminal epithelium of lambs.

Fitting of the In Vitro Gas Production Technique to the Study of High Concentrate Diets

In vitro rumen fermentation systems are often adapted to forage feeding conditions, with pH values ranging in a range close to neutrality (between 6.5 and 7.0). Several attempts using different buffers have been made to control incubation pH in order to evaluate microbial fermentation under conditions simulating high concentrate feeding, but results have not been completely successful because of rapid exhaustion of buffering capacity. Recently, a modification of bicarbonate ion concentration in the buffer of incubation solution has been proposed, which, together with using rumen inoculum from donor ruminants given high-concentrate diets, allows for mimicking such conditions in vitro. It is important to consider that the gas volume recorded is in part directly produced from microbial fermentation of substrates, but also indirectly from the buffering capacity of the medium. Thus, the contribution of each (direct and indirect) gas source to the overall production should be estimated. Another major factor affecting fermentation is the rate of passage, but closed batch systems cannot be adapted to its consideration. Therefore, a simple semicontinuous incubation system has been developed, which studies the rate and extent of fermentation by gas production at the time it allows for controlling medium pH and rate of passage by manual replacement of incubation medium by fresh saliva without including rumen inoculum. The application of this system to studies using high concentrate feeding conditions will also be reviewed here.

The potential health benefits of dietary natural plant products in age related eye diseases

In the past decade, there has been a tremendous increase in the number of cases of age-related eye diseases such as age-related macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. These diseases are the leading causes of visual impairment and blindness all over the world and are associated with many pathological risk factors such as aging, pollution, high levels of glucose (hyperglycaemia), high metabolic rates, and light exposure. These risk factors lead to the generation of uncontrollable reactive oxygen species (ROS), which causes oxidative stress. Oxidative stress plays a crucial role in the pathogenesis of age-related eye diseases through the activation of nuclear factor kappa B (NF-κB), vascular endothelial growth factor (VEGF), and lipid peroxidation, which leads to the production of inflammatory cytokines, angiogenesis, protein and DNA damages, apoptosis that causes macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. This review provides updated information on the beneficial effects of dietary natural plant products (DPNPs) against age-related eye diseases. In this review, supplementation of DPNPs demonstrated preventive and therapeutic effects on people at risk of or with age-related eye diseases due to their capacity to scavenge free radicals, ameliorate inflammatory molecules, neutralize the oxidation reaction that occurs in photoreceptor cells, decrease vascular endothelial growth factor and the blood-retinal barrier and increase the antioxidant defence system. However, further experiments and clinical trials are required to establish the daily doses of DPNPs that will safely and effectively prevent age-related eye diseases.

Potential of walnut (Juglans regia) leave ethanolic extract to modify ruminal fermentation, microbial populations and mitigate methane emission

Series of in vitro trials were conducted to evaluate dose–response effects of walnut leaf ethanolic extract (WLEE) on ruminal fermentation, microbial populations, mitigation of methane emission and acidosis prevention. The treatments were conducted according to a 5 × 3 factorial arrangement in a completely randomised design formulated to contain corn (corn-based diet, CBD) and barley grain (barley-based diet, BBD), or equal amounts of barley and corn (barley and corn diet, BCD), consisting of either basal diets alone (0) or basal diets with 250, 500, 750 or 1000 µL of WLEE (W0, W250, W500, W750 and W1000 respectively) per litre of buffered rumen fluid. Three fistulated cows fed diets containing alfalfa hay and concentrate mixes (same as the control diet) plus minerals and vitamins were used for collection of ruminal fluid. The asymptote of gas production and methane emission was decreased and lag time increased in a linear and quadratic manner with an increasing dose of WLEE (P &lt; 0.001). However, gas production rate reduced linearly as WLEE dose increased (P &lt; 0.001). Methane production was significantly reduced linearly (L) and quadratically (Q) when walnut ethanolic extract was increased from 250 to 1000 μL/L (L and Q; P &lt; 0.001). The addition of WLEE significantly altered the volatile fatty acid profile in comparison to control, reducing the molar proportion of acetate and increasing that of propionate (P &lt; 0.001), and also decreased the ammonia-N concentration (L, P &lt; 0.001). Dry-matter and organic-matter in vitro digestibility coefficients were negatively affected by WLEE supplementation (L and Q; P &lt; 0.001). Although anti-acidosis potential of WLEE was significantly lower than that of monensin, W1000 increased medium culture pH compared with uncontrolled acidosis and the lower doses of WLEE. The populations of Fibrobacter succinogenes, Ruminococcus flavefaciens and R. albus were significantly reduced by WLEE, although to different magnitudes, depending on the corn and barley grain proportions in the diet. Results of the present study indicated that increasing addition levels of WLEE have noticeable effects on rumen microbial population and fermentation characteristics. It can be concluded that WLEE can potentially be used to manipulate ruminal fermentation patterns.

The Role of Chitosan as a Possible Agent for Enteric Methane Mitigation in Ruminants

Simple Summary

Ruminant husbandry is one the largest contributors to greenhouse gas emissions from the agriculture sector, particularly of methane gas, which is a byproduct of the anaerobic fermentation of structural and non-structural carbohydrates in the rumen. Increasing the efficiency of production systems and decreasing its environmental burden is a global commitment, thus methane mitigation is a strategy in which to reach these goals by rechanneling metabolic hydrogen (H₂) into volatile fatty acids (VFA) to reduce the loss of energy as methane in the rumen, which ranges from 2% (grain rations) to 12% (poor-quality forage rations) of gross energy intake. A strategy to achieve that goal may be through the manipulation of rumen fermentation with natural compounds such as chitosan. In this review, we describe the effects of chitosan on feed intake and rumen fermentation, and present some results on methanogenesis. The main compounds with antimethanogenic properties are the secondary metabolites, which are generally classified into five main groups: saponins, tannins, essential oils, organosulfurized compounds, and flavonoids. Novel compounds of interest include chitosan obtained by the deacetylation of chitin, with beneficial properties such as biocompatibility, biodegradability, non-toxicity, and chelation of metal ions. This compound has shown its potential to modify the rumen microbiome, improve nitrogen (N) metabolism, and mitigate enteric methane (CH₄) under some circumstances. Further evaluations in vivo are necessary at different doses in ruminant species as well as the economic evaluation of its incorporation in practical rations.

Abstract

Livestock production is a main source of anthropogenic greenhouse gases (GHG). The main gases are CH₄ with a global warming potential (GWP) 25 times and nitrous oxide (N₂O) with a GWP 298 times, that of carbon dioxide (CO₂) arising from enteric fermentation or from manure management, respectively. In fact, CH₄ is the second most important GHG emitted globally. This current scenario has increased the concerns about global warming and encouraged the development of intensive research on different natural compounds to be used as feed additives in ruminant rations and modify the rumen ecosystem, fermentation pattern, and mitigate enteric CH₄. The compounds most studied are the secondary metabolites of plants, which include a vast array of chemical substances like polyphenols and saponins that are present in plant tissues of different species, but the results are not consistent, and the extraction cost has constrained their utilization in practical animal feeding. Other new compounds of interest include polysaccharide biopolymers such as chitosan, mainly obtained as a marine co-product. As with other compounds, the effect of chitosan on the rumen microbial population depends on the source, purity, dose, process of extraction, and storage. In addition, it is important to identify compounds without adverse effects on rumen fermentation. The present review is aimed at providing information about chitosan for dietary manipulation to be considered for future studies to mitigate enteric methane and reduce the environmental impact of GHGs arising from livestock production systems. Chitosan is a promising agent with methane mitigating effects, but further research is required with in vivo models to establish effective daily doses without any detrimental effect to the animal and consider its addition in practical rations as well as the economic cost of methane mitigation.

Anti-methanogenic effect of rhubarb (Rheum spp.) - An in silico docking studies on methyl-coenzyme M reductase (MCR)

The present study explored anti-methanogenic properties of rhubarb compounds using in silico analysis on methyl-coenzyme M reductase (MCR) for identifying its anti-methanogen mechanism. To identify pharmacokinetics of 35 compounds from rhubarb, molecular docking and ADME analysis were performed against MCR using AutoDockVina, FAFDrugs3 and PROTOX programs. Docking results successfully indicated three possible candidate compounds 9,10-anthracenedione, 1,8-dihydroxy-3-methyl (−6.92 kcal/mol); phthalic acid isobutyl octadecyl ester (−5.26 kcal/mol); and diisooctyl phthalate (−5.61 kcal/mol) showed minimum binding energy (kcal/mol) with the target protein MCR which catalyze the biosynthesis of rumen methane. In conclusion, the identified compounds showed the most docking fitness score against the target methyl-coenzyme M reductase and the decrease in ruminal methane emission by rhubarb might be a result of these compounds by inhibition of methanogenesis.

Scrophularia striata Extract Supports Rumen Fermentation and Improves Microbial Diversity in vitro Compared to Monensin

In the search for natural alternatives to antibiotic feed additives, we compared the efficacy of two doses of Scrophularia striata extract [S. striata-Low at 40 and S. striata-High at 80 mg g^-1 dry matter (DM)] with monensin (monensin) and a negative control in the modulation of rumen fermentation, methane production and microbial abundance in vitro. Microbes were investigated using qPCR and 16S rRNA targeted sequencing. Data showed that the addition of S. striata increased production of total short chain fatty acids (SCFA) in comparison to both monensin and control (P = 0.04). The addition of S. striata increased acetate production, and increased propionate at the higher dosage (P < 0.001). Supplementation of S. striata lowered methane production (P < 0.001) compared to control but with no effect compared to monensin. Ammonia concentration decreased by 52% (P < 0.001) with S. striata-High supplementation (4.14 mmol L^-1) compared to control, which was greater than that of monensin (36%). The diversity of rumen bacteria was reduced (P < 0.001) for monensin and S. striata for both the number of observed OTUs and the Chao1 index. Quantitative analysis of Protozoa showed a decrease in the monensin treatment (P = 0.05) compared to control. Archaea copy numbers decreased equally in both S. striata-High and monensin treatments compared to the control group. Supplementation with S. striata increased relative abundances of Fibrobacteres (P < 0.001) and Planctomycetes (P = 0.001) in comparison to both the control and monensin treatments. Significant negative correlations were observed between the abundances of Bacteroides, Fusobacterium, and Succinivibrio genera and methane (r > -0.71; P ≤ 0.001). The abundance of Fibrobacter genera and total SCFA (r = 0.86), acetate (r = 0.75), and valerate (r = -0.51; P < 0.001) correlated positively. These results suggest that S. striata supplementation at 80 mg g^-1 DM inclusion, similar to monensin, supports rumen fermentation, lowers methane and ammonia production. However, S. striata supported rumen fermentation toward higher total SCFA and propionate production, while unlike monensin still supported a diverse rumen microbiome and an increase in cellulolytic bacteria such as Fibrobacter.

Modulation of ruminal and intestinal fermentation by medicinal plants and zinc from different sources

Two experiments were conducted on sheep to determine the effect of dietary supplementation with zinc and a medicinal plant mixture on haematological parameters and microbial activity in the rumen and large intestine. In Experiment 1, 24 male lambs were randomly divided into four groups: One group was fed an unsupplemented basal diet (control), and three groups were fed a diet supplemented with 70 mg Zn/kg diet in the form of Zn sulphate (ZnSO₄ ), a Zn-chelate of glycine hydrate (Zn-Gly) or a Zn-proteinate (Zn-Pro), for five months. The ruminal content was collected separately from each lamb, and batch cultures of ruminal fluid were incubated in vitro with mixture of medicinal plants (Mix) with different roughage:concentrate ratios (800:200 and 400:600, w/w). Bioactive compounds in Mix were quantified by UPLC/MS/MS. In Experiment 2, four sheep were fed a diet consisting of meadow hay and barley grain (400:600, w/w), with Zn-Gly (70 mg Zn/kg diet), Mix (10% replacement of meadow hay) or Zn-Gly and Mix (Zn-Gly-Mix) as supplements in a Latin square design. Mix decreased total gas (p < 0.001) and methane (p < 0.01) production in vitro. In Experiment 1, caecal isobutyrate and isovalerate concentrations varied among the dietary treatments (p < 0.01). The isovalerate concentration of the zinc-supplemented groups in the distal colon was higher (p < 0.001) compared with the control. In Experiment 2, the molar proportion of isobutyrate was the highest in the faeces of the sheep fed the diet with Zn-Gly-Mix (p < 0.01). The plasma zinc concentration was higher in the groups fed a diet supplemented with zinc (p < 0.001). The haematological profile and antioxidant status did not differ between the dietary groups (p > 0.05). The diets containing medicinal plants and organic zinc thus helped to modulate the characteristics of fermentation in ruminants.

Supplementation of Pelleted Hazel (Corylus avellana) Leaves Decreases Methane and Urinary Nitrogen Emissions by Sheep at Unchanged Forage Intake

This study is the first to quantify the effects of hazel (Corylus avellana) leaves on methane and urinary nitrogen emissions, digestibility, nitrogen and the energy balance of ruminants. Four experimental pellets were produced with 0, 30% and 60% hazel leaves, the latter also with 4% polyethylene glycol. Hazel leaves gradually replaced lucerne. The diet was composed of the pellets and grass hay (80%: 20%). Six adult sheep were allocated to all four treatments in a 6 × 4 crossover design. Including hazel leaves did not affect the feed intake, but it decreased the apparent digestibility of organic matter and fibre, especially at the high level. Methane emission was reduced by up to 25 to 33% per day, per unit of intake and per unit of organic matter digested. Urinary nitrogen excretion decreased by 33 to 72% with increasing levels of hazel leaves. The treatment with polyethylene glycol demonstrated that tannins in hazel leaves caused significant shares of the effects. In conclusion, the current results indicated a significant potential of hazel leaves as forage for ruminants to mitigate methane and urinary nitrogen emissions. Even high dietary hazel leaf proportions were palatable. The lower digestibility needs to be compensated with easily digestible diet ingredients.

The effect of an isoflavonid-rich liquorice extract on fermentation, methanogenesis and the microbiome in the rumen simulation technique

Due to the antimicrobial activity of flavonoids, it has been suggested that they may provide a possible alternative to antibiotics to stimulate productivity and reduce the environmental load of ruminant agriculture. We hypothesised that an extract of liquorice, rich in prenylated isoflavonoids and particularly glabridin, might potentially improve the efficiency of nitrogen utilisation and reduce methane production in the rumen. When added to a long-term rumen simulating fermentor (RUSITEC), liquorice extract at 1 g L-1 decreased ammonia production (-51%; P < 0.001) without affecting the overall fermentation process. When added at 2 g L-1, decreases in not only ammonia production (-77%; P < 0.001), but also methane (-27%; P = 0.039) and total VFA production (-15%; P = 0.003) were observed. These effects in fermentation were probably related to a decrease in protozoa numbers, a less diverse bacteria population as well as changes in the structure of both the bacterial and archaeal communities. The inclusion of an isoflavonoid-rich extract from liquorice in the diet may potentially improve the efficiency of the feed utilisation by ruminants.

Nutrient composition and in vitro methane production of sub-tropical grass species in transitional rangeland of South Africa

The development of greenhouse gas mitigation strategies has become an important issue globally. Enteric methane (CH4) emissions from livestock do not only contribute substantially to the environmental footprint of livestock production but it also represents a loss of energy that could be channelled towards animal growth and production. In this study 14 sub-tropical grass species typical of transitional rangeland regions of South Africa were characterised in terms of ecological status, chemical composition, in vitro total gas and CH4 production. The aim of the study was 2-fold: to identify grass species that could be selected for low enteric CH4 production; evaluate the influence of rangeland ecological status on the methanogenic potential of a rangeland. Grass samples were collected by hand, air-dried, milled and analysed for nutrient composition, in vitro organic matter digestibility (IVOMD) and in vitro gas and CH4 production. Cenchrus ciliaris and Urelytrum agropyriodes produced the highest 48-h in vitro CH4 of 17.49 and 14.05 mL/g DM digested respectively. The lowest 48-h in vitro CH4 was produced by Andropogan gayanus and Bothriochloa bladhii with 5.98 and 6.08 mL/g DM digested respectively. The evaluated grass species were overall of poor quality with low CP concentrations ranging from 2.4% for Trachypogon spicatus to 6.7% for Digitaria eriantha and IVOMD ranging from 22.5% for Andropogon gayanus to 42.2% for Urelytrum agropyriodes. Decreaser grass species presented with higher in vitro CH4 production compared with Increaser I and Increaser II grass species in the present study. The results of the study emphasise the importance of including the nutritional potential of grass species for improved livestock production when evaluating grass species for possible greenhouse gas mitigation strategies.

Variation in Phenolic Composition of Knautia arvensis in Correlation with Geographic Area and Plant Organ

Knautia arvensis (family Dipsacaceae) is usually found in grasslands of Europe, but can also be found in some parts of Africa and Asia, usually in dry meadows, pastures, dry hills, and open woods. The chemical composition of this species is relatively unknown. The aim of this study was to give a phenolic profile of this plant, and to show how its phenolic composition varies depending upon plant organ and geographic origin. The chemical analysis included quantification of free phenolics soluble in methanol, esters and glycosides, and phenolics that are insoluble in methanol. Fourteen different phenolic acids and eight flavonoids were quantified in total. According to this study, the chemical composition of individual plant parts can differ tremendously within one population, which does not have to be in correspondence with chemical variability between populations. As shown in this study, the variation in chemical composition between plant parts can exceed that between different populations (from different climates, altitudes, with different environmental factors), which implies that microhabitat conditions can greatly affect the composition of some plant parts, which was shown also after PCA and HCA analysis.

Products derived from olive leaves and fruits can alter in vitro ruminal fermentation and methane production

BACKGROUND

The industrial processing of olive generates a high quantity of by-products. The objective of this study was to examine the effects of products derived from olive trees, i.e. leaves, fruits or kernels as a sole substrate (part A), and crude extract from leaves combined with a substrate (part B) on rumen microbial fermentation in an in vitro batch fermentation system. In this study, total gas production, methane production, and concentrations of volatile fatty acids (VFA) and ammonia in ruminal fluid were measured.

RESULTS

In part A, in vitro fermentation of leaves or fruits yielded a gas and total VFA production that were comparable with control substrate, while most of them produced significantly less methane (up to 55.6%) when compared to control substrate. In part B, amongst leaf extracts, only addition of chloroform extract reduced methane production, which was also associated with a decrease (P < 0.01) in gas production. This effect was associated with a significant reduction (P < 0.01) in acetate to propionate ratio and ammonia production, but not in reduction in VFA concentrations.

CONCLUSION

Olive leaf and olive leaf chloroform extract reduced ammonia production and increased the molar proportion of propionate in the rumen and can assist in developing novel feed additives for methane mitigation from the rumen. © 2016 Society of Chemical Industry.

Changes in Metabolically Active Bacterial Community during Rumen Development, and Their Alteration by Rhubarb Root Powder Revealed by 16S rRNA Amplicon Sequencing

The objective of this present study was to explore the initial establishment of metabolically active bacteria and subsequent evolution in four fractions: rumen solid-phase (RS), liquid-phase (RL), protozoa-associated (RP), and epithelium-associated (RE) through early weaning and supplementing rhubarb root powder in 7 different age groups (1, 10, 20, 38, 41, 50, and 60 d) during rumen development. Results of the 16S rRNA sequencing based on RNA isolated from the four fractions revealed that the potentially active bacterial microbiota in four fractions were dominated by the phyla Proteobacteria, Firmicutes, and Bacteroidetes regardless of different ages. An age-dependent increment of Chao 1 richness was observed in the fractions of RL and RE. The principal coordinate analysis (PCoA) indicated that samples in four fractions all clustered based on different age groups, and the structure of the bacterial community in RE was distinct from those in other three fractions. The abundances of Proteobacteria decreased significantly (P < 0.05) with age, while increases in the abundances of Firmicutes and Bacteroidetes were noted. At the genus level, the abundance of the predominant genus Mannheimia in the Proteobacteria phylum decreased significantly (P < 0.05) after 1 d, while the genera Quinella, Prevotella, Fretibacterium, Ruminococcus, Lachnospiraceae NK3A20 group, and Atopobium underwent different manners of increases and dominated the bacterial microbiota across four fractions. Variations of the distributions of some specific bacterial genera across fractions were observed, and supplementation of rhubarb affected the relative abundance of various genera of bacteria.

Climate Clever Clovers: New Paradigm to Reduce the Environmental Footprint of Ruminants by Breeding Low Methanogenic Forages Utilizing Haplotype Variation

Mitigating methane production by ruminants is a significant challenge to global livestock production. This research offers a new paradigm to reduce methane emissions from ruminants by breeding climate-clever clovers. We demonstrate wide genetic diversity for the trait methanogenic potential in Australia's key pasture legume, subterranean clover (Trifolium subterraneum L.). In a bi-parental population the broadsense heritability in methanogenic potential was moderate (H² = 0.4) and allelic variation in a region of Chr 8 accounted for 7.8% of phenotypic variation. In a genome-wide association study we identified four loci controlling methanogenic potential assessed by an in vitro fermentation system. Significantly, the discovery of a single nucleotide polymorphism (SNP) on Chr 5 in a defined haplotype block with an upstream putative candidate gene from a plant peroxidase-like superfamily (TSub_g18548) and a downstream lectin receptor protein kinase (TSub_g18549) provides valuable candidates for an assay for this complex trait. In this way haplotype variation can be tracked to breed pastures with reduced methanogenic potential. Of the quantitative trait loci candidates, the DNA-damage-repair/toleration DRT100-like protein (TSub_g26967), linked to avoid the severity of DNA damage induced by secondary metabolites, is considered central to enteric methane production, as are disease resistance (TSub_g26971, TSub_g26972, and TSub_g18549) and ribonuclease proteins (TSub_g26974, TSub_g26975). These proteins are good pointers to elucidate the genetic basis of in vitro microbial fermentability and enteric methanogenic potential in subterranean clover. The genes identified allow the design of a suite of markers for marker-assisted selection to reduce rumen methane emission in selected pasture legumes. We demonstrate the feasibility of a plant breeding approach without compromising animal productivity to mitigate enteric methane emissions, which is one of the most significant challenges to global livestock production.

Methodological factors affecting gas and methane production during in vitro rumen fermentation evaluated by meta-analysis approach

Effects of some methodological factors on in vitro measures of gas production (GP, mL/g DM), CH₄ production (mL/g DM) and proportion (% CH₄ on total GP) were investigated by meta-analysis. These factors were considered: pressure in the GP equipment (0 = constant; 1 = increasing), incubation time (0 = 24; 1 = ≥ 48 h), time of rumen fluid collection (0 = before feeding; 1 = after feeding of donor animals), donor species of rumen fluid (0 = sheep; 1 = bovine), presence of N in the buffer solution (0 = presence; 1 = absence), and ratio between amount of buffered rumen fluid and feed sample (BRF/FS; 0 = ≤ 130 mL/g DM; 1 = 130–140 mL/g DM; 2 = ≥ 140 mL/g DM). The NDF content of feed sample incubated (NDF) was considered as a continuous variable. From an initial database of 105 papers, 58 were discarded because one of the above-mentioned factors was not stated. After discarding 17 papers, the final dataset comprised 30 papers (339 observations). A preliminary mixed model analysis was carried out on experimental data considering the study as random factor. Variables adjusted for study effect were analyzed using a backward stepwise analysis including the above-mentioned variables. The analysis showed that the extension of incubation time and reduction of NDF increased GP and CH₄ values. Values of GP and CH₄ also increased when rumen fluid was collected after feeding compared to before feeding (+26.4 and +9.0 mL/g DM, for GP and CH₄), from bovine compared to sheep (+32.8 and +5.2 mL/g DM, for GP and CH₄), and when the buffer solution did not contain N (+24.7 and +6.7 mL/g DM for GP and CH₄). The increase of BRF/FS ratio enhanced GP and CH₄ production (+7.7 and +3.3 mL/g DM per each class of increase, respectively). In vitro techniques for measuring GP and CH₄ production are mostly used as screening methods, thus a full standardization of such techniques is not feasible. However, a greater harmonization of analytical procedures (i.e., a reduction in the number of available protocols) would be useful to facilitate comparison between results of different experiments.

The alkaloid gramine in the anaerobic digestion process-inhibition and adaptation of the methanogenic community

As many plant secondary metabolites have antimicrobial activity, microorganisms of the anaerobic digestion process might be affected when plant material rich in these compounds is digested. Hitherto, the effects of plant secondary metabolites on the anaerobic digestion process are poorly investigated. In this study, the alkaloid gramine, a constituent of reed canary grass, was added daily to a continuous co-digestion of grass silage and cow manure. A transient decrease of the methane yield by 17 % and a subsequent recovery was observed, but no effect on other process parameters. When gramine was infrequently spiked in higher amounts, the observed inhibitory effect was even more pronounced including a 53 % decrease of the methane yield and an increase of acetic acid concentrations up to 96 mM. However, the process recovered and the process parameters were finally at initial values (methane yield around 255 LN CH4 per gram volatile solids of substrate and acetic acid concentration lower than 2 mM). The bacterial communities of the reactors remained stable upon gramine addition. In contrast, the methanogenic community changed from a well-balanced mixture of five phylotypes towards a strong dominance of Methanosarcina (more than two thirds of the methanogenic community) while Methanosaeta disappeared. Batch inhibition assays revealed that acetic acid was only converted to methane via acetoclastic methanogenesis which was more strongly affected by gramine than hydrogenotrophic methanogenesis and acetogenesis. Hence, when acetoclastic methanogenesis is the dominant pathway, a shift of the methanogenic community is necessary to digest gramine-rich plant material.

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 (>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.

Methanogenic potential of forages consumed throughout the year by cattle in a Sahelian pastoral area

Methane (CH4) emission from ruminants in African pastoral systems may be affected by intake and type of plants, which vary highly between rainy and dry seasons. In each of two sites located in the semiarid Sahelian area of Senegal, three Gobra zebus were monitored throughout 1 year. A representative sample of their diet was obtained once every month. Diet was mainly composed of grasses, herbaceous legumes, tree and shrub foliage and pods, and dried forage residues. CH4 production and volatile fatty acid (VFA) concentration, which reflects VFA production, were determined in vitro. Crude protein, neutral detergent fibre (NDF) and acid detergent fibre were measured by near-infrared spectrophotometry. CH4 production varied between 24.6 and 35.2 mL/g forage dry matter (DM), being minimal in August (rainy season) and maximal in February (dry season). Seasonal difference disappeared when CH4 was expressed in mL/g NDF. The acetate : propionate ratio varied in the same way as CH4 (3.2 and 4.6 in August and February, respectively); VFA concentration was minimum in March and maximum in September (69.2 and 77.4 mmol/L, respectively). CH4 production was closely related to dietary NDF content (r = 0.82) and to acetate : propionate ratio (r = 0.96). For six successive periods (February to July), plant categories constituting the diet were incubated separately. Reconstituting the CH4 production and VFA concentration in the diet on the basis of the proportion of plant components gave values similar to those of the global diet (33.4 and 34.2 mL CH4/g DM and 75.9 and 70.9 mmol VFA/L, respectively). This result suggests the absence of interaction among plant components on rumen fermentation.

Effect of rhubarb (Rheum spp.) root on in vitro and in vivo ruminal methane production and a bacterial community analysis based on 16S rRNA sequence

The objective of this study was to evaluate the anti-methanogenic effect of rhubarb (Rheum spp.) on in vitro, in vivo, and bacterial community composition using Quantitative Insights into Microbial Ecology sequencing. Rhubarb root powder was tested at different concentrations (0, 0.33, 0.67, and 1.33 g/L) in vitro, and all incubations were carried out in triplicate two runs on separate days. Concentrations of 0.67 and 1.33 g/L rhubarb significantly (P < 0.05) reduced methane production and the acetate : propionate ratio compared with those of the Control, without adverse effects on total volatile fatty acids and total gas production. In the second in vivo trial, four Hanwoo (Korean native) steers (live bodyweight, 556 ± 46 kg) with a ruminal cannula were housed individually in metabolic stalls and fed a basal diet twice daily in equal amounts at 0900 hours and 2100 hours. The before rhubarb treatment (before treatment) duration was 24 days for all steers; 14 days were used for diet adaptation and 10 days were used for gas samples collected 1, 2, and 3 h after the morning feeding on Days 3, 5, 7, and 9. We used three syringe needles passed through the ruminal cannula stopper at different time points as a simple and rapid method to sample rumen gas. Thereafter, three mesh bags containing 30 g of sliced rhubarb root each were placed at different depths in the rumen of each steer for 14 days (after treatment), and gas samples were collected on Days 4, 7, 10, 12, and 13. The results showed a significant (P < 0.05) decrease in methane concentration from the rhubarb-treated steers and provide the evidence that this method would be useful for in vivo screening of anti-methanogenic feed additives or plant material. Furthermore, 16s RNA sequencing after treatment showed increases in the numbers of Prevotella, and Lactobacillus, but decreases in Methanobrevibacter. In conclusion, rhubarb had an anti-methanogenic effect in vitro and in vivo, and the increase in the number of Prevotella shifted ruminal fermentation towards propionate production.

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.

Ruminal degradation of quercetin and its influence on fermentation in ruminants

The aim of the present study was to investigate the ruminal degradation of the flavonol quercetin and to determine its potential antimicrobial effects on ruminal fermentation in cows. Ruminal degradation of quercetin (0 or 100μmol/L, respectively) as well as its influence on ruminal gas production (0, 50, or 100μmol of quercetin equivalents/L, respectively, either applied as aglycone or as its glucorhamnoside rutin) using concentrate, grass hay, and straw as substrates were investigated in vitro using the Hohenheim gas test. Additionally, the influence of quercetin on ruminal concentrations of volatile fatty acids and their molar ratio in rumen-fistulated, nonlactating cows (n=5) after intraruminal application of quercetin as aglycone or as rutin (0, 10, or 50mg of quercetin equivalents/kg of BW, respectively) was evaluated. Quercetin was rapidly and extensively degraded, whereby the disappearance of quercetin was accompanied by the simultaneous appearance of 2metabolites 3,4-dihydroxyphenylacetic acid and 4-methylcatechol. In vitro total gas and methane production were not reduced by the addition of quercetin aglycone or rutin, respectively, using concentrate, grass hay, and straw as substrates. As expected, however, effects of the substrates used were detected on total gas and methane production. Highest gas production was found with concentrate, whereas values obtained with grass hay and straw were lower. Relative methane production was highest with grass hay compared with concentrate and straw (27.1 vs. 25.0 and 25.5%). After intraruminal application of the quercetin aglycone or rutin, respectively, neither total concentration nor the molar ratio of volatile fatty acids in the rumen fluid were influenced. Results of the present study show that quercetin underlies rapid ruminal degradation, whereby 3,4-dihydroxyphenylacetic acid and 4-methylcatechol are the main metabolites, whereas the latter one most likely is formed by dehydroxylation from 3,4-dihydroxyphenylacetic acid. Regarding antimicrobial effects of quercetin, results obtained indicate that fermentation processes in the forestomachs are not substantially influenced by quercetin or rutin, respectively. With regard to potential health-promoting effects of quercetin, its application in cows, especially in the form of the better available rutin, might not be accompanied by negative effects on ruminal fermentation.