Effects of thymol and carvacrol, alone or in combination, on fermentation and microbial diversity during in vitro culture of bovine rumen microbes

Comparison of the Effects of Essential Oils from Cannabis sativa and Cannabis indica on Selected Bacteria, Rumen Fermentation, and Methane Production-In Vitro Study

This study aimed to evaluate the effects of essential oils (EOs) extracted from Cannabis sativa L. and Cannabis indica Lam. on in vitro ruminal fermentation characteristics, selected rumen microbial populations, and methane production. GC-MS analyses allowed us to identify 89 compounds in both EOs. It was found that E-β-caryophyllene predominated in C. sativa (18.4%) and C. indica (24.1%). An in vitro (Ankom) test was performed to analyse the control and monensin groups, as well as the 50 µL or 100 µL EOs. The samples for volatile fatty acids (VFAs), lactate, and microbiological analysis were taken before incubation and after 6 and 24 h. The application of EOs of C. indica resulted in an increase in the total VFAs of acetate and propionate after 6 h of incubation. The applied EOs had a greater impact on the reduction in methane production after 6 h, but no apparent effect was noted after 24 h. Lower concentrations of C. sativa and C. indica had a more pronounced effect on Lactobacillus spp. and Buryrivibrio spp. than monensin. The presented findings suggest that C. sativa and C. indica supplementation can modify ruminal fermentation, the concentrations of specific volatile fatty acids, and methane production.

Exposure of Pseudomonas aeruginosa to Cinnamaldehyde Selects Multidrug Resistant Mutants

Cinnamaldehyde (CNA), the main component of cinnamon essential oil, is one of the most active plant compounds against nosocomial pathogen Pseudomonas aeruginosa. Exposure of wild-type strain PA14 (MIC 700 µg/mL) for 5 to 10 days to fixed (900 µg/mL) or increasing (from 900 to 1400 µg/mL) concentrations of this natural antibacterial resulted in emergence of resistant mutants CNA-A1 to A3, and CNA-B1 to B7, respectively. Genome sequencing experiments showed that each of CNA-A1 to A3 mutants differed from PA14 by one SNP, and a slight increase in CNA resistance level (from 700 to 900 µg/mL). By comparison, mutants B1 to B7 were more resistant (up to 1100 µg/mL); each of them harbored multiple SNPs (from 24 to 39) likely as a consequence of alteration of DNA mismatch repair gene mutS. Of the ten mutants selected, eight contained mutations in gene nalC, which indirectly downregulates expression of the operon that codes for multidrug efflux system MexAB-OprM, and showed increased resistance (up to 16-fold versus PA14) to antibiotic molecules exported by the pump, including ß-lactams and fluoroquinolones. Of the six mutants with the highest CNA resistance, five were no longer motile because of alteration of genes flgJ, fliE and/or pilJ genes. Altogether, our data show that P. aeruginosa is able to adapt to strong electrophilic molecules such as CNA by upregulating its intrinsic efflux pump MexAB-OprM, and through less well-characterized pleiotropic changes. Whether multidrug-resistant mutants can emerge in patients using cinnamon essential oil as self-medication needs to be assessed further.

The effect of Origanum syriacum L. extract and carvacrol on the in vitro digestion, estimated digestion values, ammonia and organic acid concentrations in the fermentation fluid of lucerne herbage

The effects induced by medicinal aromatic plants in biological systems vary with the type and amount of bioactive substances these plants contain. Whether the purified form of the main chemical components of these plants, such as carvacrol and thymol, or plant volatile oils containing tens of bioactive compounds are more effective remains a question of debate. This study was aimed at providing a comparative assessment of the effects of Origanum syriacum L. (wild mountain thyme) volatile oil (OSVO) and one of its main components, carvacrol (CRV), on the in vitro ruminal degradability of lucerne herbage and methane production during the degradation of lucerne. For this purpose, wild thyme was harvested at the beginning of the flowering period, and the OSVO was extracted from the plant by steam distillation. Gas production assays were performed in five groups of ruminal fluid samples, one of which was maintained for control purposes, and the other four 40/60/80 mg/l of OSVO and 60 mg/l of CRV were added. Compared to the control group, in the samples with the added CRV and OSVO, the amounts of in vitro total gas and methane production were observed to have been affected, but no decrease was detected in the ruminal protozoa counts. The level of ammonia nitrogen was lowest in the groups, in which CRV and 40 mg/l of OSVO (P < 0.01) were added. The ruminal protozoa counts were not affected by the addition of CRV and OSVO. While the total volatile fatty acid (TVFA) and propionic acid (PA) concentrations in the in vitro fermentation fluid of lucerne herbage were low in all the groups, butyric acid was detected at a level of 40 mg/l in the group where CRV was added. The OSVO was ascertained to have induced dose-dependent alterations in the investigated in vitro digestion parameters. In result, CRV (60 mg/l) and OSVO (40 mg/l) were determined to have shown a relatively positive effect on the in vitro ruminal gas production. The anti-methanogenic effect of the plant extracts was due to the decreased digestibility of the lucerne herbage. This can have a positive impact on the environment, but the same cannot be said for the animal nutrient use and animal performance.

Astragallus mollissimus plant extract: a strategy to reduce ruminal methanogenesis

Ruminal methanogenesis is considered an inefficient process as it can result in the loss of 4 to 12% of the total energy consumed by the ruminant. Recent studies have shown that compounds such as nitroethane, 2-nitroethanol, 2-nitro-1-propanol, and 3-nitro-1-propionic acid are capable of inhibiting methane production during in vitro studies. However, all of these nitrocompounds came from a synthetic origin, which could limit their use. In contrast, some plants of the Astragallus genus produce a natural nitrocompound, although its anti-methanogenic effect has not been evaluated. To determine the anti-methanogenic effect, in vitro cultures of freshly collected mixed populations of ruminal microbes were supplemented with A. mollissimus extracts (MISER). Cultures supplemented with 2-nitroethanol, ethyl 2-nitroacetate, or nitroethane were used as positive controls whereas distilled water was added to the untreated control tubes. After a 24 h incubation period, the methane production was reduced by more than 98% for the samples treated with A. mollissimus extract (P < 0.05) compared to the untreated controls (10.2 ± 0.1 mmol mL^-1 incubated liquid). Cultures supplemented with MISER produced a greater (P < 0.05) amount of total VFA, compared to the rest of treated and untreated cultures. Considering that there are significant differences between MISER treatment, positive controls and untreated cultures (P < 0.05) regarding the amounts of total gas, gas composition (CH₄ and H₂), and the amount of VFA produced, it is concluded that Astragallus mollissimus poses an alternative strategy to reduce ruminal methanogenesis. To further explore such alternative, it is necessary to determine if the metabolization byproducts are safe and/or useful for the animal.

Research progress on the application of feed additives in ruminal methane emission reduction: a review

BACKGROUND

Ruminal methane (CH4) emissions from ruminants not only pollute the environment and exacerbate the greenhouse effect, but also cause animal energy losses and low production efficiency. Consequently, it is necessary to find ways of reducing methane emissions in ruminants. Studies have reported that feed additives such as nitrogen-containing compounds, probiotics, prebiotics, and plant extracts significantly reduce ruminant methane; however, systematic reviews of such studies are lacking. The present article summarizes research over the past five years on the effects of nitrogen-containing compounds, probiotics, probiotics, and plant extracts on methane emissions in ruminants. The paper could provide theoretical support and guide future research in animal production and global warming mitigation.

METHODS

This review uses the Web of Science database to search keywords related to ruminants and methane reduction in the past five years, and uses Sci-Hub, PubMed, etc. as auxiliary searchers. Read, filter, list, and summarize all the retrieved documents, and finally complete this article.

RESULTS

Most of the extracts can not only significantly reduce CH4 greenhouse gas emissions, but they will not cause negative effects on animal and human health either. Therefore, this article reviews the mechanisms of CH4 production in ruminants and the application and effects of N-containing compounds, probiotics, prebiotics, and plant extracts on CH4 emission reduction in ruminants based on published studies over the past 5 years.

CONCLUSION

Our review provides a theoretical basis for future research and the application of feed additives in ruminant CH4 emission reduction activities.

Phytogenic Additives Can Modulate Rumen Microbiome to Mediate Fermentation Kinetics and Methanogenesis Through Exploiting Diet-Microbe Interaction

Ruminants inhabit the consortia of gut microbes that play a critical functional role in their maintenance and nourishment by enabling them to use cellulosic and non-cellulosic feed material. These gut microbes perform major physiological activities, including digestion and metabolism of dietary components, to derive energy to meet major protein (65-85%) and energy (ca 80%) requirements of the host. Owing to their contribution to digestive physiology, rumen microbes are considered one of the crucial factors affecting feed conversion efficiency in ruminants. Any change in the rumen microbiome has an imperative effect on animal physiology. Ruminal microbes are fundamentally anaerobic and produce various compounds during rumen fermentation, which are directly used by the host or other microbes. Methane (CH4) is produced by methanogens through utilizing metabolic hydrogen during rumen fermentation. Maximizing the flow of metabolic hydrogen in the rumen away from CH4 and toward volatile fatty acids (VFA) would increase the efficiency of ruminant production and decrease its environmental impact. Understanding of microbial diversity and rumen dynamics is not only crucial for the optimization of host efficiency but also required to mediate emission of greenhouse gases (GHGs) from ruminants. There are various strategies to modulate the rumen microbiome, mainly including dietary interventions and the use of different feed additives. Phytogenic feed additives, mainly plant secondary compounds, have been shown to modulate rumen microflora and change rumen fermentation dynamics leading to enhanced animal performance. Many in vitro and in vivo studies aimed to evaluate the use of plant secondary metabolites in ruminants have been conducted using different plants or their extract or essential oils. This review specifically aims to provide insights into dietary interactions of rumen microbes and their subsequent consequences on rumen fermentation. Moreover, a comprehensive overview of the modulation of rumen microbiome by using phytogenic compounds (essential oils, saponins, and tannins) for manipulating rumen dynamics to mediate CH4 emanation from livestock is presented. We have also discussed the pros and cons of each strategy along with future prospective of dietary modulation of rumen microbiome to improve the performance of ruminants while decreasing GHG emissions.

Effects of Thymol Supplementation on Goat Rumen Fermentation and Rumen Microbiota In Vitro

This study was performed to explore the predominant responses of rumen microbiota with thymol supplementation as well as effective dose of thymol on rumen fermentation. Thymol at different concentrations, i.e., 0, 100 mg/L, 200 mg/L, and 400 mg/L (four groups × five replications) was applied for 24 h of fermentation in a rumen fluid incubation system. Illumina MiSeq sequencing was applied to investigate the ruminal microbes in addition to the examination of rumen fermentation. Thymol doses reached 200 mg/L and significantly decreased (p < 0.05) total gas production (TGP) and methane production; the production of total volatile fatty acids (VFA), propionate, and ammonia nitrogen, and the digestibility of dry matter and organic matter were apparently decreased (p < 0.05) when the thymol dose reached 400 mg/L. A thymol dose of 200 mg/L significantly affected (p < 0.05) the relative abundance of 14 genera of bacteria, three species of archaea, and two genera of protozoa. Network analysis showed that bacteria, archaea, and protozoa significantly correlated with methane production and VFA production. This study indicates an optimal dose of thymol at 200 mg/L to facilitate rumen fermentation, the critical roles of bacteria in rumen fermentation, and their interactions with the archaea and protozoa.

Antioxidant, Anti-Inflammatory, and Microbial-Modulating Activities of Essential Oils: Implications in Colonic Pathophysiology

Essential oils (EOs) are a complex mixture of hydrophobic and volatile compounds synthesized from aromatic plants, most of them commonly used in the human diet. In recent years, many studies have analyzed their antimicrobial, antioxidant, anti-inflammatory, immunomodulatory and anticancer properties in vitro and on experimentally induced animal models of colitis and colorectal cancer. However, there are still few clinical studies aimed to understand their role in the modulation of the intestinal pathophysiology. Many EOs and some of their molecules have demonstrated their efficacy in inhibiting bacterial, fungi and virus replication and in modulating the inflammatory and oxidative processes that take place in experimental colitis. In addition to this, their antitumor activity against colorectal cancer models makes them extremely interesting compounds for the modulation of the pathophysiology of the large bowel. The characterization of these EOs is made difficult by their complexity and by the different compositions present in the same oil having different geographical origins. This review tries to shift the focus from the EOs to their individual compounds, to expand their possible applications in modulating colon pathophysiology.