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Simple Summary: This study was conducted to explore the optimal level of Rheum palmatum root (RP) for the mitigation of enteric methane and demonstrate the effects on methane production and rumen fermentation characteristics in cattle fed with RP. In the in vitro trial, 3% of RP addition most effectively reduced methane production, which determined the feeding level for the test subjects in the in vivo trial. In the in vivo trial, RP addition did not affect methane emissions in the steers, likely due to the adaptation of ruminal microorganisms to the RP addition. This study investigated the impact of Rheum palmatum root (RP) for reducing methane and its impact on rumen fermentation and blood metabolites in cattle. Rumen fluid was collected from three cannulated steers (736 ± 15 kg) and mixed with buffer (1:3 ratio) for the in vitro trial. Treatments were divided into control and RP supplement groups (1%, 3%, and 5% of substrates), with each sample incubated at 39 °C for 24 and 48 hours. Methane was measured after incubation, showing a dose-dependent linear decrease after 48 hours. Quadratic changes were observed in total volatile fatty acids, acetate, and butyrate. Additionally, in vitro dry matter digestibility decreased linearly with RP inclusion. In vivo trials involved four Korean steers in a 2 × 2 crossover design over 3 weeks, with treatments including a control group and a group with 3% RP addition. Dry matter intake (DMI) tended to decrease in the RP group compared to the control. Methane emissions (g/kg DMI) were not affected by RP addition. Blood metabolites indicated higher lipase concentrations in the RP group. In conclusion, RP reduced methane production in the in vitro trial but had no effect in the in vivo trial, likely due to adaptation of ruminal bacteria to RP. [ABSTRACT FROM AUTHOR]

Simple Summary: Due to economic, environmental, and nutritional considerations, mitigating enteric methane production from ruminants is an important issue. Nutritionists have recently shown that feeding livestock natural feed additives could ameliorate this problem, due to the antimicrobial activities of the biologically active components in the additives. Bamboo is widely distributed in Asia and is currently being used in construction and paper pulp production, which results in a significant amount of bamboo leaves as by-products. The present study investigated whether bamboo leaves feeding can decrease methane production in ruminants. Here we found that bamboo leaves supplementation in vitro caused a 12.7–34.2% reduction in methane production after 12 and 48 h. Further studies are needed to demonstrate the effect of bamboo leaves supplementation in vivo, to determine its potential for mitigating methane production from ruminants. Ruminants produce large amounts of methane as part of their normal digestive processes. Recently, feed additives were shown to inhibit the microorganisms that produce methane in the rumen, consequently reducing methane emissions. The objective of this study was to evaluate the dose–response effect of Phyllostachys nigra var. henonis (PHN) and Sasa borealis supplementation on in vitro rumen fermentation, methane, and carbon dioxide production, and the microbial population. An in vitro batch culture system was used, incubated without bamboo leaves (control) or with bamboo leaves (0.3, 0.6, and 0.9 g/L). After 48 h, total gas, methane, and carbon dioxide production decreased linearly with an increasing dose of bamboo leaves supplementation. The total volatile fatty acid, acetate, and acetate-to-propionate ratio were affected quadratically with increasing doses of bamboo leaves supplementation. In addition, propionate decreased linearly. Butyrate was increased linearly with increasing doses of PHN supplementation. The absolute values of total bacteria and methanogenic archaea decreased linearly and quadratically with an increasing dose of PHN treatment after 48 h. These results show that bamboo leaves supplementation can reduce methane production by directly affecting methanogenic archaea, depressing the metabolism of methanogenic microbes, or transforming the composition of the methanogenic community. These results need to be validated using in vivo feeding trials before implementation. [ABSTRACT FROM AUTHOR]

We identified metabolites in the seeds of Pharbitis nil (PA) and evaluated their effects on rumen methanogenesis, fiber digestibility, and the rumen microbiome in vitro and in sacco. Four rumen-cannulated Holstein steers (mean body weight 507 ± 32 kg) were used as inoculum donor for in vitro trial and live continuous culture system for in sacco trial. PA was tested in vitro at doses ranging from 4.5 to 45.2% dry matter (DM) substrate. The in sacco trial was divided into three phases: a control phase of 10 days without nylon bags containing PA in the rumen, a treatment phase of 11 days in which nylon bags containing PA (180 g) were placed in the rumen, and a recovery phase of 10 days after removing the PA-containing bags from the rumen. Rumen headspace gas and rumen fluid samples were collected directly from the rumen. PA is enriched in polyunsaturated fatty acids dominated by linoleic acid (C18:2) and flavonoids such as chlorogenate, quercetin, quercetin-3- O -glucoside, and quinic acid derivatives. PA decreased (p < 0.001) methane (CH4) production linearly in vitro with a reduction of 24% at doses as low as 4.5% DM substrate. A quadratic increase (p = 0.078) in neutral detergent fiber digestibility was also noted, demonstrating that doses < 9% DM were optimal for simultaneously enhancing digestibility and CH4 reduction. In sacco , a 50% decrease (p = 0.087) in CH4 coupled with an increase in propionate suggested increased biohydrogenation in the treatment phase. A decrease (p < 0.005) in ruminal ammonia nitrogen (NH3-N) was also noted with PA in the rumen. Analysis of the rumen microbiome revealed a decrease (p < 0.001) in the Bacteroidetes-to-Firmicutes ratio, suggesting PA to have antiprotozoal potential. At the genus level, a 78% decrease in Prevotella spp. and a moderate increase in fibrolytic Ruminococcus spp. were noted in the treatment phase. In silico binding of PA metabolites to cyclic GMP-dependent protein kinase of Entodinium caudatum supported the antiprotozoal effect of PA. Overall, based on its high nutrient value and antiprotozoal activity, PA could probably replace the ionophores used for CH4 abatement in the livestock industry. [ABSTRACT FROM AUTHOR]

Simple Summary: Methane from ruminants is a major contributor to total greenhouse gases. Therefore, ruminant nutritionists have proposed strategies to mitigate methane emissions, such as chemical inhibitors and ionophores. However, dietary manipulation including natural feed additives is more practical, considering consumer preferences. Therefore, the current experiment screened 137 plant species, indigenous to East Asian countries, to select novel anti-methanogenic candidates as natural feed additives. Among these species, an extract from the seeds of Pharbitis nil exhibited a maximum 37% reduction of methane in a conformation assay. Identification of active compounds present in the seeds of Pharbitis nil revealed enrichment of polyunsaturated fatty acids, which were dominated by linoleic acid (18:2). The extract had negative effects on the populations of ciliated protozoa and H2-producing Ruminococcus flavefaciens, thereby increasing the proportion of propionate, similar to the effect of monensin. This is the first report to suggest that the seeds of P. nil could be a promising anti-methanogenic alternative to ionophores or oil seeds. 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. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the potential of Pinus koraiensis cone essential oil (PEO) on in vitro fermentation, methane (CH 4) production and microbiota quantification in three different in vitro experiments. First, the main active compounds present in PEO were identified and quantified. Subsequently, the in vitro fermentation characteristics and CH 4 production after PEO supplementation (0.20 g/L) at different ratios of forage-to-concentrate (F:C, 100:0, 70:30, 50:50, 30:70, and 0:100; Experiment 1) were evaluated. At a F:C ratios of 50:50, control (CON) and PEO supplementation led to similar total volatile fatty acid concentrations, while CH 4 production (13.7%) significantly reduced. Based on this result, we determined that 50:50 F:C ratio can serve as an appropriate diet ratio to evaluate dose-response PEO supplementation. The effects of three levels of PEO supplementation (0.20, 0.50, and 1.0 g/L) on CH 4 production, fermentation, and microbiota were then determined in vitro (Experiment 2). Methane production decreased (P < 0.001) with increasing PEO supplementation, with a reduction of up to 65% at 1.0 g/L levels at 24 h of incubation compared with that in the CON. However, PEO supplementation exhibited adverse effects (P < 0.05) on the abundance of most ciliate protozoa, fungi, and fibrolytic bacteria, including Fibrobacter succinogenes , Ruminococcus albus , and Ruminococcus flavefaciens. In contrast, the abundance of CH 4 -producing archaea (total methanogens and Methanobrevibacter sp. AbM4) was greater (P < 0.05) than that in the CON. Furthermore, the effects of PEO supplementation using in vitro continuous culture system for a total of 16 d (including 7 d for adaptation and 9 d for fermentation; Experiment 3) were examined. Methane production was reduced (P < 0.001) (47.1%) upon PEO supplementation compared with that in the CON. Similar to Experiment 2, in vitro fermentation and microbiota were affected (P < 0.05) in response to PEO supplementation. In all three experiments, butyrate was greater (P < 0.001) under PEO supplementation than that in the CON. In addition, butyrate-producing bacteria (Butyrivibrio proteoclasticus) were less sensitive to PEO and contributed to the increased butyrate in the continuous cultures. However, all three in vitro results showed that reduction in CH 4 production was accompanied by decreased fermentation parameters. These results suggest that although PEO supplementation can reduce CH 4 production, it can alter in vitro fermentation and microbiota, such that the supplementation of a great concentrations of PEO may not be beneficial to ruminants. • Pinus koraiensis cone essential oil (PEO) can reduce methane (CH 4) production in ruminants by up to 65% at 1.0 g/L levels. • PEO supplementation (0.20 g/L) at a 50:50 F:C (forage to concentrate) ratio resulted in significant reductions in CH 4 production parameters while maintaining similar total VFA concentrations. • PEO supplementation can alter in vitro fermentation and microbiota, with adverse effects on ciliate protozoa, fungi, and fibrolytic bacteria. • Butyrate-producing bacteria were less sensitive to PEO, contributing to increased butyrate in continuous cultures. [ABSTRACT FROM AUTHOR]