Use of Lactic Acid Bacteria to Reduce Methane Production in Ruminants, a Critical Review

Deciphering the role of Moringa oleifera seeds and probiotic bacteria on mitigation of biogas production from ruminants

Maintaining cleaner and more sustainable ecosystems by mitigating greenhouse gas (GHG) emissions from livestock through dietary manipulation is in demand. This study was aimed to assess the effect of Moringa oleifera seeds and probiotics (Pediococcus acidilactici BX-B122 and Bacillus coagulans BX-B118) as feed supplements on GHG production and fermentation profile from steers and sheep. The treatments included diets containing 0, 6, 12, and 18% of M. oleifera seeds meal and a mixture of probiotic bacteria (0.2 ml/g of diet). Total biogas production, CH4, CO, and H2S emission from animals (up to 48 h), rumen fermentation profile, and CH4 conversion efficiency were recorded using standard protocols. Results showed interaction among M. oleifera seeds and probiotics on asymptotic biogas production and total biogas production up to 48 h (P < 0.05). The rate of CH4 emission in steers was reduced from 0.1694 to 0.0447 ml/h using 6 and 18% of M. oleifera seeds (P < 0.05). Asymptotic CO and the rate of CO production were increased (P < 0.05) by supplementing different doses of M. oleifera seeds and probiotics. Adding 12% of M. oleifera seeds and probiotics reduced H2S production from 0.0675 to 0.0112 ml H2S/g DM (at 48 h of fermentation) in steers. In sheep, the additives mitigated H2S production from 0.0364 to 0.0029 ml H2S/g DM (at 48 h of fermentation), however there were not interaction (P = 0.7744). In addition, M. oleifera seeds and probiotics reduced the pH level and dry matter degradability (DMD) in steers and sheep (P < 0.0001) showing a positive impact on CH4:ME and CH4:OM (in steers) and CH4:SCFA (in sheep), while the interaction was not significant (P > 0.05) for CH4:SCFA (in steers) and CH4:ME and CH4:OM (in sheep). In conclusion, the interaction of M. oleifera seeds and probiotics in the feeding diet reduced GHG emissions and affected the fermentation profile of steers and sheep.

The ruminant gut microbiome vs enteric methane emission: The essential microbes may help to mitigate the global methane crisis

Ruminants release enteric methane into the atmosphere, significantly increasing greenhouse gas emissions and degrading the environment. A common focus of traditional mitigation efforts is on dietary management and manipulation, which may have limits in sustainability and efficacy, exploring the potential of essential microorganisms as a novel way to reduce intestinal methane emissions in ruminants; a topic that has garnered increased attention in recent years. Fermentation and feed digestion are significantly aided by essential microbes found in the rumen, such as bacteria, fungi, and archaea. The practical implications of the findings reported in various studies conducted on rumen gut concerning methane emissions may pave the way to understanding the mechanisms of CH4 production in the rumen to enhance cattle feed efficiency and mitigate CH4 emissions from livestock. This review discussed using essential bacteria to reduce intestinal methane emissions in ruminants. It investigates how particular microbial strains or consortia can alter rumen fermentation pathways to lower methane output while preserving the health and productivity of animals. We also describe the role of probiotics and prebiotics in managing methane emissions using microbial feed additives. Further, recent studies involving microbial interventions have been discussed. The use of new methods involving functional metagenomics and meta-transcriptomics for exploring the rumen microbiome structure has been highlighted. This review also emphasizes the challenges faced in altering the gut microbiome and future directions in this area.

Meta-analysis of the relationship between dietary starch intake and enteric methane emissions in cattle from in vivo experiments

Objective

Different sources and levels of starch in the total mixed ration might result in different rumen fermentation profiles, rumen microbial composition, and enteric methane production. The current study aimed to evaluate the effect of dietary starch intake on enteric methane production through a meta-analytical approach by integrating related published studies.

Materials and Methods

Papers that provided study results on enteric methane production from cattle fed different sources and levels of starch were selected. A total of 52 publications were filtered based on some specified criteria, comprised of 73 studies focused on enteric methane production in cattle fed a basal diet supplemented with starch. The collected data were subjected to statistical meta-analysis through a mixed methodology model. The p-value and root mean square error (RMSE) were applied as the statistical models.

Results

Results showed that increasing the level of dietary starch intake and its digestibility in the rumen as well as increasing propionate significantly decreased the acetate to propionate (A/P) ratio as well as enteric methane production (p < 0.01).

Conclusions

It is concluded that the addition of starch to diets mitigates enteric methane production from cattle, primarily through two ways, i.e., manipulation of the protozoa population and alteration to a lower A/P ratio.

Strategies for reducing noxious gas emissions in pig production: a comprehensive review on the role of feed additives

The emission of noxious gases is a significant problem in pig production, as it can lead to poor production, welfare concerns, and environmental pollution. The noxious gases are the gasses emitted from the pig manure that contribute to air pollution. The increased concentration of various harmful gasses can pose health risks to both animals and humans. The major gases produced in the pig farm include methane, hydrogen sulfide, carbon dioxide, ammonia, sulfur dioxide and volatile fatty acids, which are mainly derived from the fermentation of undigested or poorly digested nutrients. Nowadays research has focused on more holistic approaches to obtain a healthy farm environment that helps animal production. The use of probiotics, prebiotics, dietary enzymes, and medicinal plants in animal diets has been explored as a means of reducing harmful gas emissions. This review paper focuses on the harmful gas emissions from pig farm, the mechanisms of gas production, and strategies for reducing these emissions. Additionally, various methods for reducing gas in pigs, including probiotic interventions; prebiotic interventions, dietary enzymes supplementation, and use of medicinal plants and organic acids are discussed. Overall, this paper provides a comprehensive review of the current state of knowledge on reducing noxious gas in pigs and offers valuable insights for pig producers, nutritionists, and researchers working in this area.

Synthetic Communities of Gut Microbes for Basic Research and Translational Approaches in Animal Health and Nutrition

Microbes and animals have a symbiotic relationship that greatly influences nutrient uptake and animal health. This relationship can be studied using selections of microbes termed synthetic communities, or SynComs. SynComs are used in many different animal hosts, including agricultural animals, to investigate microbial interactions with nutrients and how these affect animal health. The most common host focuses for SynComs are currently mouse and human, from basic mechanistic research through to translational disease models and live biotherapeutic products (LBPs) as treatments. We discuss SynComs used in basic research models and findings that relate to human and animal health and nutrition. Translational use cases of SynComs are discussed, followed by LBPs, especially within the context of agriculture. SynComs still face challenges, such as standardization for reproducibility and contamination risks. However, the future of SynComs is hopeful, especially in the areas of genome-guided SynCom design and custom SynCom-based treatments.

Recent Advances in Enteric Methane Mitigation and the Long Road to Sustainable Ruminant Production

Mitigation of methane emission, a potent greenhouse gas, is a worldwide priority to limit global warming. A substantial part of anthropogenic methane is emitted by the livestock sector, as methane is a normal product of ruminant digestion. We present the latest developments and challenges ahead of the main efficient mitigation strategies of enteric methane production in ruminants. Numerous mitigation strategies have been developed in the last decades, from dietary manipulation and breeding to targeting of methanogens, the microbes that produce methane. The most recent advances focus on specific inhibition of key enzymes involved in methanogenesis. But these inhibitors, although efficient, are not affordable and not adapted to the extensive farming systems prevalent in low- and middle-income countries. Effective global mitigation of methane emissions from livestock should be based not only on scientific progress but also on the feasibility and accessibility of mitigation strategies.

A Review of Potential Feed Additives Intended for Carbon Footprint Reduction through Methane Abatement in Dairy Cattle

Eight rumen additives were chosen for an enteric methane-mitigating comparison study including garlic oil (GO), nitrate, Ascophyllum nodosum (AN), Asparagopsis (ASP), Lactobacillus plantarum (LAB), chitosan (CHI), essential oils (EOs) and 3-nitrooxypropanol (3-NOP). Dose-dependent analysis was carried out on selected feed additives using a meta-analysis approach to determine effectiveness in live subjects or potential efficacy in live animal trials with particular attention given to enteric gas, volatile fatty acid concentrations, and rumen microbial counts. All meta-analysis involving additives GO, nitrates, LAB, CHI, EOs, and 3-NOP revealed a reduction in methane production, while individual studies for AN and ASP displayed ruminal bacterial community improvement and a reduction in enteric CH4. Rumen protozoal depression was observed with GO and AN supplementation as well as an increase in propionate production with GO, LAB, ASP, CHI, and 3-NOP rumen fluid inoculation. GO, AN, ASP, and LAB demonstrated mechanisms in vitro as feed additives to improve rumen function and act as enteric methane mitigators. Enzyme inhibitor 3-NOP displays the greatest in vivo CH4 mitigating capabilities compared to essential oil commercial products. Furthermore, this meta-analysis study revealed that in vitro studies in general displayed a greater level of methane mitigation with these compounds than was seen in vivo, emphasising the importance of in vivo trials for final verification of use. While in vitro gas production systems predict in vivo methane production and fermentation trends with reasonable accuracy, it is necessary to confirm feed additive rumen influence in vivo before practical application.

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.

Autumn grass treated with a hydrolysable tannin extract versus lactic acid bacteria inoculant: Effects on silage fermentation characteristics and nutritional value and on performance of lactating dairy cows

Hydrolysable tannins (HT) show potential as silage additive for autumn herbage silages, high in (rumen degradable) protein, as they may reduce proteolysis. Additionally, they have abilities to form pH-reversible tannin-protein complexes, non-degradable in the rumen but degradable in the abomasum and intestines of ruminants. Therefore they can improve milk N efficiency and shift N excretions from urine to faeces, possibly mitigating the environmental impact of ruminants. In this study, two small bunker silos were filled with autumn grass. One was treated with 20 g/kg DM HT extract (TAN) (TannoSan-L), the other with 8 mg/kg DM inoculant containing lactic acid bacteria (INO) (Bonsilage Fit G). Secondly, micro-silos (2.75 L) were filled with four treatments; (1) grass without additive (CON) (n = 5); (2) TAN (n = 5); (3) INO (n = 5); and (4) TAN + INO (n = 5). The bunker silos were used in a cross-over feeding experiment with periods of 4 weeks involving 22 lactating Holstein cows (average ± SD: 183 ± 36.3 days in milk, 665 ± 71.0 kg body weight, and 33.8 ± 3.91 kg/day milk yield). The HT dose was insufficient to reduce proteolysis or alter chemical composition and nutritional value in the micro- and bunker silages. Including grass silage added with TAN (3.2 g HT/kg DM) in the diet, did not affect feed intake nor fat and protein corrected milk yield in comparison to feeding the grass silage added with INO in a similar diet. The TAN-fed cows had an increased faecal N excretion and decreased apparent total-tract N and organic matter digestibility, but no improvement in the cows' N utilization could be confirmed in milk and blood urea levels. Overall, feeding an autumn grass silage treated with 20 g/kg chestnut HT extract did not affect the performance of dairy cows in comparison to feeding an autumn grass silage treated with a lactic acid bacteria inoculant.

Holistic View and Novel Perspective on Ruminal and Extra-Gastrointestinal Methanogens in Cattle

Despite the extensive research conducted on ruminal methanogens and anti-methanogenic intervention strategies over the last 50 years, most of the currently researched enteric methane (CH4) abatement approaches have shown limited efficacy. This is largely because of the complex nature of animal production and the ruminal environment, host genetic variability of CH4 production, and an incomplete understanding of the role of the ruminal microbiome in enteric CH4 emissions. Recent sequencing-based studies suggest the presence of methanogenic archaea in extra-gastrointestinal tract tissues, including respiratory and reproductive tracts of cattle. While these sequencing data require further verification via culture-dependent methods, the consistent identification of methanogens with relatively greater frequency in the airway and urogenital tract of cattle, as well as increasing appreciation of the microbiome-gut-organ axis together highlight the potential interactions between ruminal and extra-gastrointestinal methanogenic communities. Thus, a traditional singular focus on ruminal methanogens may not be sufficient, and a holistic approach which takes into consideration of the transfer of methanogens between ruminal, extra-gastrointestinal, and environmental microbial communities is of necessity to develop more efficient and long-term ruminal CH4 mitigation strategies. In the present review, we provide a holistic survey of the methanogenic archaea present in different anatomical sites of cattle and discuss potential seeding sources of the ruminal methanogens.

Dietary Ruminant Enteric Methane Mitigation Strategies: Current Findings, Potential Risks and Applicability

This review examines the current state of knowledge regarding the effectiveness of different dietary ruminant enteric methane mitigation strategies and their modes of action together with the issues discussed regarding the potential harms/risks and applicability of such strategies. By investigating these strategies, we can enhance our understanding of the mechanisms by which they influence methane production and identify promising approaches for sustainable mitigation of methane emissions. Out of all nutritional strategies, the use of 3-nitrooxypropanol, red seaweed, tannins, saponins, essential oils, nitrates, and sulfates demonstrates the potential to reduce emissions and receives a lot of attention from the scientific community. The use of certain additives as pure compounds is challenging under certain conditions, such as pasture-based systems, so the potential use of forages with sufficient amounts of plant secondary metabolites is also explored. Additionally, improved forage quality (maturity and nutrient composition) might help to further reduce emissions. Red seaweed, although proven to be very effective in reducing emissions, raises some questions regarding the volatility of the main active compound, bromoform, and challenges regarding the cultivation of the seaweed. Other relatively new methods of mitigation, such as the use of cyanogenic glycosides, are also discussed in this article. Together with nitrates, cyanogenic glycosides pose serious risks to animal health, but research has proven their efficacy and safety when control measures are taken. Furthermore, the risks of nitrate use can be minimized by using probiotics. Some of the discussed strategies, namely monensin or halogenated hydrocarbons (as pure compounds), demonstrate efficacy but are unlikely to be implemented widely because of legal restrictions.

Longitudinal transkingdom gut microbial approach towards decompensation in outpatients with cirrhosis

OBJECTIVE

First decompensation development is a critical milestone that needs to be predicted. Transkingdom gut microbial interactions, including archaeal methanogens, may be important targets and predictors but a longitudinal approach is needed.

DESIGN

Cirrhosis outpatients who provided stool twice were included. Group 1: compensated, group 2: 1 decompensation (decomp), group 3: >1 decompensationwere followed and divided into those who remained stable or decompensated. Bacteria, viral and archaeal presence, α/β diversity and taxa changes over time adjusted for clinical variables were analysed. Correlation networks between kingdoms were analysed.

RESULTS

157 outpatients (72 group 1, 33 group 2 and 52 group 3) were followed and 28%-47% developed outcomes. Baseline between those who remained stable/developed outcome: While no α/β diversity differences were seen, commensals were lower and pathobionts were higher in those who decompensated. After decompensation: those experiencing their first decompensation showed greater decrease in α/β-diversity, bacterial change (↑Lactobacillus spp, Streptococcus parasanguinis and ↓ beneficial Lachnospiraceae and Eubacterium hallii) and viral change (↑Siphoviridae, ↓ Myoviridae) versus those with further decompensation. Archaea: 19% had Methanobacter brevii, which was similar between/within groups. Correlation networks: Baseline archaeal-viral-bacterial networks were denser and more homogeneous in those who decompensated versus the rest. Archaea-bacterial correlations collapsed post first decompensation. Lactobacillus phage Lc Nu and C2-like viruses were negatively linked with beneficial bacteria.

CONCLUSION

In this longitudinal study of cirrhosis outpatients, the greatest transkingdom gut microbial changes were seen in those reaching the first decompensation, compared with subsequent decompensating events. A transkingdom approach may refine prediction and provide therapeutic targets to prevent cirrhosis progression.

Methanobrevibacter boviskoreani JH1T growth on alcohols allows development of a high throughput bioassay to detect methanogen inhibition

Rumen methanogenic archaea use by-products of fermentation to carry out methanogenesis for energy generation. A key fermentation by-product is hydrogen (H₂), which acts as the source of reducing potential for methane (CH₄) formation in hydrogenotrophic methanogens. The in vitro cultivation of hydrogenotrophic rumen methanogens requires pressurised H₂ which limits the ability to conduct high-throughput screening experiments with these organisms. The genome of the hydrogenotrophic methanogen Methanobrevibacter boviskoreani JH1^T harbors genes encoding an NADP-dependent alcohol dehydrogenase and a F₄₂₀-dependent NADP reductase, which may facilitate the transfer of reducing potential from ethanol to F₄₂₀ via NADP. The aim of this study was to explore the anaerobic culturing of JH1^T without pressurised H₂, using a variety of short chain alcohols. The results demonstrate that in the absence of H₂, JHI^T can use ethanol, 1-propanol, and 1-butanol but not methanol, as a source of reducing potential for methanogenesis. The ability to use ethanol to drive CH₄ formation in JH1^T makes it possible to develop a high throughput culture-based bioassay enabling screening of potential anti-methanogen compounds. The development of this resource will help researchers globally to accelerate the search for methane mitigation technologies for ruminant animals. Global emissions pathways that are consistent with the temperature goal of the Paris Agreement, rely on substantial reductions of agricultural greenhouse gasses, particularly from ruminant animals.

Invited review: Rumen modifiers in today's dairy rations

Our aim was to review feed additives that have a potential ruminal mechanism of action when fed to dairy cattle. We discuss how additives can influence ruminal fermentation stoichiometry through electron transfer mechanisms, particularly the production and usage of dihydrogen. Lactate accumulation should be avoided, especially when acidogenic conditions suppress ruminal neutral detergent fiber digestibility or lead to subclinical acidosis. Yeast products and other probiotics are purported to influence lactate uptake, but growing evidence also supports that yeast products influence expression of gut epithelial genes promoting barrier function and resulting inflammatory responses by the host to various stresses. We also have summarized methane-suppressing additives for potential usage in dairy rations. We focused on those with potential to decrease methane production without decreasing fiber digestibility or milk production. We identified some mitigating factors that need to be addressed more fully in future research. Growth factors such as branched-chain volatile fatty acids also are part of crucial cross-feeding among groups of microbes, particularly to optimize fiber digestibility in the rumen. Our developments of mechanisms of action for various rumen-active modifiers should help nutrition advisors anticipate when a benefit in field conditions is more likely.

The Effect of Direct-Fed Lactobacillus Species on Milk Production and Methane Emissions of Dairy Cows

Using direct-fed microbials to mitigate enteric methane emissions could be sustainable and acceptable to both consumers and producers. Forty lactating, multiparous, Holstein-Friesian cows were randomly allocated one of two treatments: (1) a base of ad libitum vetch (Vicia sativa) hay and 7.0 kg DM/d of a grain mix, or (2) the basal diet plus 10 mL of MYLO® (Terragen Biotech Pty Ltd., Coolum Beach, Queensland, Australia) delivering 4.17 × 108 cfu of Lactobacillus per mL. Neither feed intake (25.4 kg/d vs. 24.8 kg/d) nor milk yield (29.9 vs. 30.3 kg/d) were affected by treatment. Feed conversion efficiency was not affected by treatment when expressed on an energy-corrected milk basis (1.15 vs. 1.18 kg/kg DMI). Neither methane yield (31.6 vs. 31.1 g/kg DMI) nor methane intensity (27.1 vs. 25.2 g/kg energy corrected milk) were affected by treatments. While these results are contrary to our expectations and not significant, all were numerically in a favorable direction. Given there are reports that diet and dose rate may impact the size of any effect, we recommend a dose–response study be undertaken using a basal diet that is commonly used in pasture-based dairy systems.

Effect of supplementation with ruminal probiotics on growth performance, carcass characteristics, plasma metabolites, methane emissions, and the associated rumen microbiome changes in beef cattle

To evaluate the effect of supplementing beef cattle with a ruminal probiotic consisting of native rumen microbes (NRM; Chordicoccus furentiruminis, Prevotella albensis, and Succinivibrio dextrinosolvens) on methane (CH4) emissions, growth performance, carcass characteristics, and plasma metabolites, Angus × SimAngus-crossbred steers (n = 32; 8 per pen) and heifers (n = 48; 12 per pen) with an initial body weight (BW) of 353 ± 64 kg were used in randomized complete block design. Cattle were blocked by sex and BW and randomly assigned to 1 of 2 treatments (2 pens per treatment). Treatments consisted of diets offered for ad libitum intake with (NRM) or without (CON) the inclusion of the ruminal probiotic. Cattle were fed a growing diet for 49 d followed by a ground corn-based diet for 124 ± 27 d until reaching the targeted final BW (635 kg for steers and 590 kg for heifers). Methane emissions were estimated using the GreenFeed system (n = 12 per treatment) prior to trial commencement (baseline; period 1), and on three (2, 3, and 4), and two (5 and 6) different sampling periods throughout the growing and finishing stage, respectively. All data were analyzed using the PROC MIXED procedure of SAS. For CH4 production (g/d), there was a tendency for an NRM supplementation × period interaction (P = 0.07) where cattle-fed diets with NRM had lower production of methane in periods 3 and 4. Including NRM in the diet decreased CH4 yield (g/kg of dry matter intake (DMI)) by 20%. For CH4 emission intensity (g/kg of average daily gain (ADG)), an interaction (P < 0.01) of NRM supplementation × period occurred. In periods 2 and 3, cattle-fed diets with NRM inclusion had lower CH4 emission intensity than CON cattle. During the 84-d period when all cattle were still on the finishing diet, feeding NRM increased (P = 0.02) ADG and tended to increase (P = 0.10) DMI. At the end of the 84-d period, cattle-fed NRM tended to be heavier (P = 0.06) than CON cattle. Cattle supplemented with NRM required less (P = 0.04) days on feed to reach the targeted final BW. No differences (P ≤ 0.11) were detected for gain-to-feed ratio and carcass characteristics. Cattle-fed NRM had greater abundance of uncultured rumen bacteria that may improve rumen digestion when fed a high grain diet and potentially promote the reduction of enteric CH4 production. Results from this study suggest that daily administration of NRM may be a strategy to mitigate methanogenesis and improve the growth performance of beef cattle.

Effects of Dietary Capsaicin and Yucca schidigera Extracts as Feed Additives on Rumen Fermentation and Microflora of Beef Cattle Fed with a Moderate-Energy Diet

Capsaicin (CAP) and Yucca schidigera extract (YSE) are two types of plant extracts that can change rumen fermentation. This study was conducted to investigate whether supplementation of beef cattle diets with CAP and YSE for 90 days would affect rumen fermentation and microflora. Forty-five healthy Angus steers (initial body weight = 510.54 ± 41.27 kg) were divided into three groups: control (CON), CAP, and YSE. Ammonia nitrogen (NH3-N) and total volatile fatty acid (TVFA) concentrations were significantly higher in the YSE group than in the CON group and significantly lower in the CAP group than in the CON group. At the phylum level, YSE increased the relative abundances of Bacteroidota and Patescibacteria and reduced that of Bacillota. At the genus level, CAP and YSE both increased the relative abundances of genera subordinate to Bacteroidota and decreased the relative abundances of genera subordinate to Bacillota. Our study shows that YSE and CAP have different effects on rumen fermentation and microflora after long-term supplementation.

Lacticaseibacillus rhamnosus HN001 alters the microbiota composition in the cecum but not the feces in a piglet model

The probiotic Lacticaseibacillus rhamnosus strain HN001 has been shown to have several beneficial health effects for both pediatric and maternal groups, including reduced risk of eczema in infants and gestational diabetes and postnatal depression in mothers. While L. rhamnosus HN001 appears to modify immune and gut barrier biomarkers, its mode of action remains to be fully elucidated. To gain insights into the role of HN001 on the infant microbiome, the impacts of L. rhamnosus HN001 supplementation was studied in 10-day old male piglets that were fed either infant formula, or infant formula with L. rhamnosus HN001 at a low (1.3 × 10⁵ CFU/ml) or high dose (7.9 × 10⁶ CFU/ml) daily for 24 days. The cecal and fecal microbial communities were assessed by shotgun metagenome sequencing and host gene expression in the cecum and colon tissue was assessed by RNA-seq. Piglet fecal samples showed only modest differences between controls and those receiving dietary L. rhamnosus HN001. However, striking differences between the three groups were observed for cecal samples. While total lactobacilli were significantly increased only in the high dose L. rhamnosus HN001 group, both high and low dose groups showed an up to twofold reduction across the Firmicutes phylum and up to fourfold increase in Prevotella compared to controls. Methanobrevibacter was also decreased in HN001 fed piglets. Microbial genes involved in carbohydrate and vitamin metabolism were among those that differed in relative abundance between those with and without L. rhamnosus HN001. Changes in the cecal microbiome were accompanied by increased expression of tight junction pathway genes and decreased autophagy pathway genes in the cecal tissue of piglets fed the higher dose of L. rhamnosus HN001. Our findings showed supplementation with L. rhamnosus HN001 caused substantial changes in the cecal microbiome with likely consequences for key microbial metabolic pathways. Host gene expression changes in the cecum support previous research showing L. rhamnosus HN001 beneficially impacts intestinal barrier function. We show that fecal samples may not adequately reflect microbiome composition higher in the gastrointestinal tract, with the implication that effects of probiotic consumption may be missed by examining only the fecal microbiome.

Innovations for Reducing Methane Emissions in Livestock toward a Sustainable System: Analysis of Feed Additive Patents in Ruminants

Simple Summary

The mitigation of the environmental impact of animal production is a global objective, and innovation can provide new strategies and technologies to support the transition toward a more sustainable livestock system. Using patent data analysis to identify innovation dynamics, we explored the sector of feed additives to reduce methane emissions in ruminants. We found that this innovation sector is recent and rapidly expanding, with the European Union representing the center of innovation. The most promising inventions are related to the use of beneficial microorganisms (probiotics) and plant-based extracts.

Abstract

An important challenge for livestock systems is the mitigation of environmental impacts while ensuring food security, and feed additives are considered as one of the most promising mitigation strategies. This study analyzed the innovation landscape of feed additives to reduce methane emissions in ruminants. The analysis is based on patent data to evaluate the development, scientific importance, and market-level impact of the innovations in this field. The results reveal that the EU is on the innovation frontier, with substantial and quality patent production. The innovation field is dominated by private players, characterized by high specificity in the R&D pipeline. Additives derived from plant or botanical extracts, together with 3-nitrooxypropanol (3-NOP), represent the emerging innovations, indicating a clear orientation toward more sustainable livestock systems. Despite the regulatory and semantic limitations related to the use of patent databases, data reveal a growing innovation activity at global level, which could lead to macroeconomic benefits for the entire livestock sector.

A newly developed strain of Enterococcus faecium isolated from fresh dairy products to be used as a probiotic in lactating Holstein cows

The objective of this study was to determine the ability of an isolated strain (EGY_NRC1) or commercial (NCIMB 11181) Enterococcus faecium as a probiotic for lactating cows. Two experiments were conducted: In Experiment 1, the effects of three levels (1, 2, and 3 g/kg diet, DM basis) of isolated and commercial E. faecium on in vitro ruminal fermentation kinetics, gas, methane (CH₄) and nutrient degradability were determined. In Experiment 2, thirty multiparous Holstein cows (633 ± 25.4 kg body weight) with 7 days in milk, were randomly assigned to 3 treatments in a completely randomized design in a 60-day experiment. Cows were fed without any additives (control treatment) or supplemented with 2 g/kg feed daily of E. faecium EGY_NRC1 (contain 1.1 × 10⁹ CFU/g) or commercial E. faecium NCIMB 11181 (contain 2 × 10¹² CFU/g). Diets were prepared to meet cow's nutrient requirements according to NRC recommendations. Probiotic doses were based on the in vitro Experiment 1. Feed intake, digestibility, blood parameters and lactation performance were evaluated. In Experiment 1, the isolated E. faecium linearly and quadratically increased (P < 0.001) in vitro total gas production (TGP), the degradability of dry matter (dDM) and organic matter (dOM) while decreased (P < 0.05) methane (CH₄) percent of TGP, NH₃CH₄ production, and pH. The commercial E. faecium increased TGP and decreased (P < 0.01) CH₄ production, pH and increased the dDM and dOM, short chain fatty acids and ruminal NH₃-N concentration. In Experiment 2, the isolated E. faecium increased (P < 0.01) total tract digestibility of DM, neutral and acid detergent fiber, daily milk production and feed efficiency compared to the control treatment without affecting feed intake and milk composition. Moreover, the isolated E. faecium increased (P < 0.05) the proportion of C18:1 trans-9, C18:2 cis-9-12 and C18:2 trans-10 cis-12. Both isolated and commercial E. faecium improved (P < 0.01) organic matter, crude protein and nonstructural carbohydrates digestibility, increased serum glucose (P = 0.002) and decreased serum cholesterol (P = 0.002). Additionally, both E. faecium strains decreased C23:0 (P = 0.005) in milk. In conclusion, the use of E. faecium (isolated and commercial) at 2 g/kg DM of feed improved feed efficiency and production performance, with superior effects on animal performance from isolated E. faecium compared to the commercial one.

Changes in rumen fermentation and bacterial profiles after administering Lactiplantibacillus plantarum as a probiotic

Background and Aim: Lactiplantibacillus plantarum is one of the lactic acid bacteria that is often used as probiotics. This study aimed to evaluate the effects of Lactiplantibacillus plantarum TSD10 as a probiotic on rumen fermentation and microbial population in Ongole breed cattle. Materials and Methods: This study adopted an experimental crossover design, using three-fistulated Ongole breed cattle. Treatments were as follows: T0, control without probiotic; T1, 10 mL probiotic/day; T2, 20 mL probiotic/day; and T3, 30 mL probiotic/day. The basal diet of the cattle comprised 70% concentrate: 30% elephant grass (Pennisetum purpureum). The concentration of probiotic used was 1.8 × 1010 colony-forming unit (CFU)/mL. Results: We observed significantly lower acetate production compared with control (64.12%), the lowest values being in the T3 group (55.53%). Contrarily, propionate production significantly increased from 18.67% (control) to 23.32% (T2). All treatments yielded significantly lower acetate–propionate ratios than control (3.44), with the lowest ratio in the T3 group (2.41). The protozoal number decreased on probiotic supplementation, with the lowest population recorded in the T2 group (5.65 log cells/mL). The population of specific rumen bacteria was estimated using a quantitative polymerase chain reaction. We found that the population of L. plantarum, Ruminococcus flavefaciens, and Treponema bryantii, did not change significantly on probiotic supplementation, While that of Ruminococcus albus increased significantly from 9.88 log CFU/mL in controls to 12.62 log CFU/mL in the T2 group. Conclusion: This study showed that the optimum dosage of L. plantarum TSD10 as a probiotic was 20 mL/day. The effect of L. plantarum as a probiotic on feed degradation in rumen was not evaluated in this experiment. Therefore, the effect of L. plantarum as a probiotic on feed degradation should be performed in further studies.

Antimicrobial Peptides Controlling Resistant Bacteria in Animal Production

In the last few decades, antimicrobial resistance (AMR) has been a worldwide concern. The excessive use of antibiotics affects animal and human health. In the last few years, livestock production has used antibiotics as food supplementation. This massive use can be considered a principal factor in the accelerated development of genetic modifications in bacteria. These modifications are responsible for AMR and can be widespread to pathogenic and commensal bacteria. In addition, these antibiotic residues can be dispersed by water and sewer water systems, the contamination of soil and, water and plants, in addition, can be stocked in tissues such as muscle, milk, eggs, fat, and others. These residues can be spread to humans by the consumption of water or contaminated food. In addition, studies have demonstrated that antimicrobial resistance may be developed by vertical and horizontal gene transfer, producing a risk to public health. Hence, the World Health Organization in 2000 forbid the use of antibiotics for feed supplementation in livestock. In this context, to obtain safe food production, one of the potential substitutes for traditional antibiotics is the use of antimicrobial peptides (AMPs). In general, AMPs present anti-infective activity, and in some cases immune response. A limited number of AMP-based drugs are now available for use in animals and humans. This use is still not widespread due to a few problems like in-vivo effectiveness, stability, and high cost of production. This review will elucidate the different AMPs applications in animal diets, in an effort to generate safe food and control AMR.

Bovine host genome acts on rumen microbiome function linked to methane emissions

Our study provides substantial evidence that the host genome affects the comprehensive function of the microbiome in the rumen of bovines. Of 1,107/225/1,141 rumen microbial genera/metagenome assembled uncultured genomes (RUGs)/genes identified from whole metagenomics sequencing, 194/14/337 had significant host genomic effects (heritabilities ranging from 0.13 to 0.61), revealing that substantial variation of the microbiome is under host genomic control. We found 29/22/115 microbial genera/RUGs/genes host-genomically correlated (|0.59| to |0.93|) with emissions of the potent greenhouse gas methane (CH4), highlighting the strength of a common host genomic control of specific microbial processes and CH4. Only one of these microbial genes was directly involved in methanogenesis (cofG), whereas others were involved in providing substrates for archaea (e.g. bcd and pccB), important microbial interspecies communication mechanisms (ABC.PE.P), host-microbiome interaction (TSTA3) and genetic information processes (RP-L35). In our population, selection based on abundances of the 30 most informative microbial genes provided a mitigation potential of 17% of mean CH4 emissions per generation, which is higher than for selection based on measured CH4 using respiration chambers (13%), indicating the high potential of microbiome-driven breeding to cumulatively reduce CH4 emissions and mitigate climate change.

Probiotics: Symbiotic Relationship with the Animal Host

Antibiotic growth-promoters in animal feeding are known to generate bacterial resistance on commercial farms and have proven deleterious effects on human health. This review addresses the effects of probiotics and their symbiotic relationship with the animal host as a viable alternative for producing healthy meat, eggs, and milk at present and in the future. Probiotics can tolerate the conditions of the gastrointestinal tract, such as the gastric acid, pH and bile salts, to exert beneficial effects on the host. They (probiotics) may also have a beneficial effect on productivity, health and wellbeing in different parameters of animal performance. Probiotics stimulate the native microbiota (microbes that are present in their place of origin) and production of short-chain fatty acids, with proven effects such as antimicrobial, hypocholesterolemic and immunomodulatory effects, resulting in better intestinal health, nutrient absorption capacity and productive responses in ruminant and non-ruminant animals. These beneficial effects of probiotics are specific to each microbial strain; therefore, the isolation and identification of beneficial microorganisms, as well as in vitro and in vivo testing in different categories of farm animals, will guarantee their efficacy, replicability and sustainability in the current production systems.

Effect of Feeding Discarded Durian Peel Ensiled with Lactobacillus casei TH14 and Additives in Total Mixed Rations on Digestibility, Ruminal Fermentation, Methane Mitigation, and Nitrogen Balance of Thai Native–Anglo-Nubian Goats

The objective of this study was to evaluate the effect of fermented discarded durian peel with Lactobacillus casei TH14, cellulase, and molasses separately or in combination in total mixed rations on feed utilization, digestibility, ruminal fermentation, and nitrogen utilization in growing crossbreed Thai Native–Anglo-Nubian goats. Five crossbreed Thai Native–Anglo-Nubian goats (50%) at 9 to 12 months of age and 20 ± 1 of body weight (BW) were assigned to a 5 × 5 Latin square design. Evaluated treatments were fermented discarded durian peel without additives (FDP), fermented discarded durian peel with 5% of molasses (FDPM), fermented discarded durian peel with 2% of cellulase (FDPC), fermented discarded durian peel with 1.0 × 105 cfu/g fresh matter of L. casei TH14 (FDPL), and fermented discarded durian peel with 5% of molasses and 1.0 × 105 cfu/g fresh matter of L. casei TH14 (FDPML). This study showed that acid detergent fiber intake was different (p < 0.05) between goats fed FDP and those fed FDPLM, 0.24 g/d and 0.20 g/d, respectively. The FDPML ration had significantly (p < 0.05) greater apparent nutrient digestibility and a better propionate concentration compared with other treatments. FDPML treatment significantly (p < 0.05) decreased the acetate-to-propionate ratio, methane production, and urinary nitrogen. Therefore, treated discarded durian peel with molasses and L. casei TH14 in combination could add 25% of dry matter into the diet for growing goats without a negative impact.

Alternative pathways for hydrogen sink originated from the ruminal fermentation of carbohydrates: Which microorganisms are involved in lowering methane emission?

Agriculture is responsible for a great share of the anthropogenic sources of greenhouse gases that, by warming the earth, threaten its biodiversity. Among greenhouse gas emissions, enteric CH4 from livestock is an important target to slow down climate changes. The CH4 is originated from rumen fermentation and its concentration is affected by several factors, including genetics and nutrition. Ruminants have an extraordinary symbiosis with microorganisms (bacteria, fungi, and protozoa) that ferment otherwise indigestible carbohydrates, from which they obtain energy to grow and continue actively producing, among other products, volatile fatty acids, CO2 and H2. Detrimental ruminal accumulation of H2 is avoided by methanogenesis carried out by Archaea methanogens. Importantly, methanogenesis is not the only H2 sink pathway. In fact, other bacteria can reduce substrates using metabolic hydrogen formed during carbohydrate fermentation, namely propionate production and reductive acetogenesis, thus lowering the CH4 produced. Although the complexity of rumen poses challenges to mitigate CH4 production, the emergence of sequencing techniques that allow the study of microbial communities, gene expression, and metabolome are largely contributing to unravel pathways and key players in the rumen. Indeed, it is now recognized that in vivo emissions of CH4 are correlated to microbial communities, and particularly with the abundance of methanogens, several bacterial groups, and  their genes. The goal of CH4 mitigation is to work in favor of the natural processes, without compromising rumen function, animal health, and productivity. Notwithstanding, the major challenge continues to be the feasibility and affordability of the proposed solutions.

Effects of Selenium Supplementation on Rumen Microbiota, Rumen Fermentation, and Apparent Nutrient Digestibility of Ruminant Animals: A Review

Enzymes excreted by rumen microbiome facilitate the conversion of ingested plant materials into major nutrients (e.g., volatile fatty acids (VFA) and microbial proteins) required for animal growth. Diet, animal age, and health affect the structure of the rumen microbial community. Pathogenic organisms in the rumen negatively affect fermentation processes in favor of energy loss and animal deprivation of nutrients in ingested feed. Drawing from the ban on antibiotic use during the last decade, the livestock industry has been focused on increasing rumen microbial nutrient supply to ruminants through the use of natural supplements that are capable of promoting the activity of beneficial rumen microflora. Selenium (Se) is a trace mineral commonly used as a supplement to regulate animal metabolism. However, a clear understanding of its effects on rumen microbial composition and rumen fermentation is not available. This review summarized the available literature for the effects of Se on specific rumen microorganisms along with consequences for rumen fermentation and digestibility. Some positive effects on total VFA, the molar proportion of propionate, acetate to propionate ratio, ruminal NH3-N, pH, enzymatic activity, ruminal microbiome composition, and digestibility were recorded. Because Se nanoparticles (SeNPs) were more effective than other forms of Se, more studies are needed to compare the effectiveness of synthetic SeNPs and lactic acid bacteria enriched with sodium selenite as a biological source of SeNPs and probiotics. Future studies also need to evaluate the effect of dietary Se on methane emissions.

Challenges and opportunities for the production of lactic acid bacteria inoculants aimed for ensiling processes

The use of bacterial inoculants for ensiling based on lactic acid bacteria (LAB) to obtain conserved forages has become an alternative for the improvement of milk and meat productivity in cattle, specifically by optimizing the nutritional and microbial quality of animal feed. LAB inoculant production involves microbial and technological aspects such as biomass obtention, the use of cocultures, the inclusion of probiotics, the production of antimicrobial peptides, operational methods used in bioreactors, and the formulation of the end product to be commercialized to farmers. This review explores the technical aspects of the manufacture of bacterial inoculants, from the main features desired in LAB for ensiling purposes to the alternatives of the bioprocess involved.

Isolation and Identification of a Rumen Lactobacillus Bacteria and Its Degradation Potential of Gossypol in Cottonseed Meal during Solid-State Fermentation

Cottonseed meal (CSM) is an important protein feed source for dairy cows. Its inclusion in ruminant diets is limited due to the presence of the highly toxic gossypol though rumen microorganisms are believed to be capable of gossypol degrading and transforming. The objective of the present study was to isolate the gossypol-degrading bacteria from the rumen contents and to assess its potential for gossypol degradation in vitro. A strain named Lactobacillus agilis WWK129 was anaerobically isolated from dairy cows after mixed rumen microorganisms were grown on a substrate with gossypol as the sole carbon source. Furthermore, the strain was applied at 5% inoculum concentration in vitro to continuously ferment CSM at 39 °C for five days, and it presented gossypol degradability as high as 83%. Meanwhile, the CSM contents of crude protein, essential amino acids increased significantly along with the increase of lactic acid yield (p < 0.01). Compared with the original CSM, the fermented CSM contents of neutral detergent fiber and acid detergent fiber was remarkably decreased after the anaerobic fermentation (p < 0.01). In brief, the Lactobacillus strain isolated from the rumen is not only of great importance for gossypol biodegradation of CSM, but it could also be used to further explore the role of rumen microorganisms in gossypol degradation by the ruminants.

Implication and challenges of direct-fed microbial supplementation to improve ruminant production and health

Direct-fed microbials (DFMs) are feed additives containing live naturally existing microbes that can benefit animals' health and production performance. Due to the banned or strictly limited prophylactic and growth promoting usage of antibiotics, DFMs have been considered as one of antimicrobial alternatives in livestock industry. Microorganisms used as DFMs for ruminants usually consist of bacteria including lactic acid producing bacteria, lactic acid utilizing bacteria and other bacterial groups, and fungi containing Saccharomyces and Aspergillus. To date, the available DFMs for ruminants have been largely based on their effects on improving the feed efficiency and ruminant productivity through enhancing the rumen function such as stabilizing ruminal pH, promoting ruminal fermentation and feed digestion. Recent research has shown emerging evidence that the DFMs may improve performance and health in young ruminants, however, these positive outcomes were not consistent among studies and the modes of action have not been clearly defined. This review summarizes the DFM studies conducted in ruminants in the last decade, aiming to provide the new knowledge on DFM supplementation strategies for various ruminant production stages, and to identify what are the potential barriers and challenges for current ruminant industry to adopt the DFMs. Overall literature research indicates that DFMs have the potential to mitigate ruminal acidosis, improve immune response and gut health, increase productivity (growth and milk production), and reduce methane emissions or fecal shedding of pathogens. More research is needed to explore the mode of action of specific DFMs in the gut of ruminants, and the optimal supplementation strategies to promote the development and efficiency of DFM products for ruminants.

The Use of Organic Acids (Lactic and Acetic) as a Microbial Decontaminant during the Slaughter of Meat Animal Species: A Review

Wild ungulate species provide a much-needed protein source to many communities in developed and developing countries. Frequently, these game meat animals are slaughtered, and the meat is unknowingly contaminated by microorganisms and released to the unsuspecting public. This review investigates the global usage of organic acids (lactic and acetic acids) as microbial decontamination strategies during slaughter. The results show that there is a more open-minded approach to adopting possible decontamination plans as a tool to improve meat safety during slaughter. Developed countries continue to adopt these strategies, while developing countries are lagging behind. While decontamination of carcasses can lead to a reduction of microbial load on these carcasses, this strategy must not be seen as a replacement of hygiene management during the animals’ slaughter.

Role of Exposure to Lactic Acid Bacteria from Foods of Animal Origin in Human Health

Animal products, in particular dairy and fermented products, are major natural sources of lactic acid bacteria (LAB). These are known for their antimicrobial properties, as well as for their roles in organoleptic changes, antioxidant activity, nutrient digestibility, the release of peptides and polysaccharides, amino acid decarboxylation, and biogenic amine production and degradation. Due to their antimicrobial properties, LAB are used in humans and in animals, with beneficial effects, as probiotics or in the treatment of a variety of diseases. In livestock production, LAB contribute to animal performance, health, and productivity. In the food industry, LAB are applied as bioprotective and biopreservation agents, contributing to improve food safety and quality. However, some studies have described resistance to relevant antibiotics in LAB, with the concomitant risks associated with the transfer of antibiotic resistance genes to foodborne pathogens and their potential dissemination throughout the food chain and the environment. Here, we summarize the application of LAB in livestock and animal products, as well as the health impact of LAB in animal food products. In general, the beneficial effects of LAB on the human food chain seem to outweigh the potential risks associated with their consumption as part of animal and human diets. However, further studies and continuous monitorization efforts are needed to ensure their safe application in animal products and in the control of pathogenic microorganisms, preventing the possible risks associated with antibiotic resistance and, thus, protecting public health.

Manipulation of Rice Straw Silage Fermentation with Different Types of Lactic Acid Bacteria Inoculant Affects Rumen Microbial Fermentation Characteristics and Methane Production

Bacterial inoculants are known to improve the quality of silage. The objectives of the present study were to evaluate the effects of different types of lactic acid bacteria (LAB; L. plantarum, L. salivarius, L. reuteri, L. brevi, and S. bovis) inoculation (10⁶ cfu/ DM) on rice straw silage quality and to determine these effects on ruminal fermentation characteristics, digestibility and microbial populations in an in vitro condition. Inoculated rice straw was ensiled for 15 and 30 days. For the in vitro study, rumen fluid was obtained from three rumen-fistulated bulls fed on mixed forage and concentrate at 60:40 ratio twice daily. Inoculation with LAB improved (p < 0.05) the rice straw silage quality as indicated by higher dry matter and crude protein contents, decreased pH and butyric acid, and increased propionic acid and LAB numbers, especially after 30 days of ensiling. Results from the in vitro study revealed that starting with the addition of LAB to rice straw silage improved in vitro fermentation characteristics such as increased total volatile fatty acids and dry matter digestibility (p < 0.05). LAB treatments also decreased methane production and methane/total gas ratio after 15 and 30 days of ensiling. From the rumen microbial population perspective, cellulolytic, and fungal zoospores were enhanced, while protozoa and methanogens were decreased by the LAB treatments. Based on these results, it could be concluded that inoculating rice straw silage with LAB (especially for L. plantarum and S. bovis) improved silage quality, rumen fermentation parameters and microbial populations in vitro.

Influence of three microbial feed additives of Megasphaera elsdenii, Saccharomyces cerevisiae and Lactobacillus sp. on ruminal methane and carbon dioxide production, and biofermentation kinetics

AIMS

This study was performed to investigate the effects of Megasphaera elsdenii (Me), Saccharomyces cerevisiae (SC) and lactic acid bacteria (FP-Lactobacillus fermentum plus Lactobacillus plantarum) alone or in combination on biogas production and ruminal biofermentation parameter in a heterofermenter system.

METHODS AND RESULTS

Eight treatments were evaluated; (i) control (without additive; CON); (ii) Me; (iii) SC; (iv) FP; (v) Me plus SC (MSC); (vi) Me plus FP (MFP); (vii) SC plus FP (SCFP) and (viii) Me plus SC plus FP (MSCFP). Doses of FP, Me and SC were 1·5 × 10⁸ (CFU per ml), 1·5 × 10⁸ (CFU per ml) and 1·4 × 10⁷ (CFU 0·002^-1  g), respectively. Biogas production in all time increased (P < 0·05) by MSCFP than CON additive. The proportional methane (CH₄ ) decreased (P < 0·05) in MSCFP and FP, while carbon dioxide (CO₂ ) was decreased (P < 0·05) by SC compared MSCFP and MSC. The proportional CO₂ decreased (P < 0·05) by MSCFP and FP additive. The mean concentration of NH₃ -N was not affected by treatments. Concentration of total volatile fatty acids and the percent of acetate and propionate was not affected by treatments. The highest (P < 0·05) percent of butyrate and valerate were observed in MSCFP additive. The experiment showed that microbial additives of FP, SCFP and MSCFP reduced proportional CH₄ and CO₂ .

CONCLUSIONS

Microbial additives of MFP and MSCFP had a sustainable positive efficiency on pH and volatile fatty acids and mitigate CH₄ and CO₂ .

SIGNIFICANCE AND IMPACT OF THE STUDY

The use of microbial additives control on the ruminal pH (MFP) and improve VFA such as butyrate (MSC, MSCFP) and valerate (MSCFP) and reduce the greenhouse gases production showed a reduced risk of ruminal acidosis.

Complete genome sequencing of Peyer's patches-derived Lactobacillus taiwanensis CLG01, a potential probiotic with antibacterial and immunomodulatory activity

Background

The genus Lactobacillus is an important component of the gastrointestinal tract of human and animals and commonly considered as probiotic. L. taiwanensis has long been proposed to be a probiotic whereas understanding on this species is still in its infancy. Genomic information of L. taiwanensis is fairly limited. Extensive characterization of its beneficial traits is needed.

Results

A new strain CLG01 of L. taiwanensis was isolated from mouse Peyer’s patches. We established its probiotic profile through in vitro experiments. Complete genome of this strain was also sequenced and analyzed. L. taiwanensis CLG01 showed robust tolerance to acid and a degree of tolerance to bile salt with a promising antibacterial activity against a broad spectrum of pathogenic bacteria. In vitro treatment of mouse RAW 264.7 macrophage cells with heat-killed bacteria and bacterial supernatant of L. taiwanensis CLG01 resulted in enhancement of immune responses and upregulated expression of TNF-α and IL-6. The strain CLG01 also increased the IL-10 production of macrophages when co-treated with lipopolysaccharide (LPS). Complete genome of L. taiwanensis CLG01 contained a 1.89 Mb chromosome and two plasmids. Further genomic analysis revealed the presence of genes related to its resistance to different stresses and the beneficial effects mentioned above. Moreover, biosynthetic gene clusters (BGCs) encoding antimicrobial peptides, like bacteriocin, linear azol(in)e-containing peptide (LAP) and lanthipeptide, were also identified in the genome of L. taiwanensis CLG01.

Conclusions

L. taiwanensis CLG01, isolated from mouse Peyer’s patches, is the first L. taiwanensis strain with both phenotypes and genotypes systematically studied. These preliminary data confirmed the role of L. taiwanensis CLG01 as a potential probiotic candidate with antibacterial and immunomodulatory activity, which provide insight for further investigation to this species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02127-z.

The Start-Up of Continuous Biohydrogen Production from Cheese Whey: Comparison of Inoculum Pretreatment Methods and Reactors with Moving and Fixed Polyurethane Carriers

This article presents the results of the start-up of continuous production of biohydrogen from cheese whey (CW) in an anaerobic filter (AF) and anaerobic fluidized bed (AFB) with a polyurethane carrier. Heat and acid pretreatments were used for the inactivation of hydrogen-scavengers in the inoculum (mesophilic and thermophilic anaerobic sludge). Acid pretreatment was effective for thermophilic anaerobic sludge to suppress methanogenic activity, and heat treatment was effective for mesophilic anaerobic sludge. Maximum specific yields of hydrogen, namely 178 mL/g chemical oxygen demand (COD) and 149 mL/g COD for AFB and AF, respectively, were obtained at the hydraulic retention time (HRT) of 4.5 days and organic load rate (OLR) of 6.61 kg COD/(m3 day). At the same time, the maximum hydrogen production rates of 1.28 and 1.9 NL/(L day) for AF and AFB, respectively, were obtained at the HRT of 2.02 days and OLR of 14.88 kg COD/(m3 day). At the phylum level, the dominant taxa were Firmicutes (65% in AF and 60% in AFB), and at the genus level, Lactobacillus (40% in AF and 43% in AFB) and Bifidobacterium (24% in AF and 30% in AFB).

A comparative study of artificial cow and sheep rumen fermentation of corn straw and food waste: Batch and continuous operation

To optimize the artificial rumen microorganism sources and develop a stable artificial rumen system, batch and continuous operation were investigated with corn straw and food waste as substrates. The batch trials evaluated the volatile fatty acid (VFA) yield, biogas production, and lignocellulose degradation efficiency. The continuous test evaluated the performance of the artificial cow and sheep rumen systems using a dynamic membrane bioreactor (DMBR) with a stepwise organic loading rate at mesophilic temperature. The anaerobic digestion (AD) of the lignocellulose biomass after rumen fermentation pretreatment and of the permeate from the artificial rumen system were also evaluated for CH₄ production. The results indicated that the cow rumen microorganisms were more suitable than sheep rumen microorganisms for lignocellulosic biomass pretreatment and maximized the CH₄ yield through the AD process without inhibition. After approximately four months of continuous operation, a stable and continuous artificial rumen system for lignocellulosic biomass degradation was achieved with cow rumen fluid as inoculum. Based on analysis of the core lignocellulose-degrading enzyme levels and gel filtration chromatography, the cow rumen microorganisms could secrete more extracellular multienzyme complexes to hydrolyze lignocellulosic biomass than the sheep rumen microorganisms in vitro. During the batch and continuous operations, a high diversity and similar richness of bacteria and fungi demonstrated that the cow rumen microorganisms can be used as a preferred inoculum for the artificial rumen system. The use of an artificial cow rumen system with a DMBR is a promising way to construct a stable and continuous artificial rumen system to biodegrade lignocellulosic biomass for biogas production.

Ozone Decreased Enteric Methane Production by 20% in an in vitro Rumen Fermentation System

Ozone (O₃) is volatile, highly oxidative, and has theoretical potential to reduce ruminant enteric methanogenesis by interactions between archaea and bacteria, and substrate and oxygen. The effects of O₃ on the rumen microbiota, fermentation parameters, and CH₄ emissions were studied through in vitro fermentation using a RUSITEC apparatus with O₃ dissolved in the salivary buffer. The substrate consisted of maize silage or grain concentrates, and the treatments were (1) control (no O₃) and (2) O₃ at 0.07 ± 0.022 mg/L in the buffer. A 4-day adaptation period followed by a 6-day experimental period was used for measuring gas production and composition, as well as fermentation characteristics, which included ruminal volatile fatty acids (VFA) and liquid- and solid-associated microbial communities. Ozone treatment decreased total gas production by 15.4%, most notably CH₄ production by 20.4%, and CH₄ gas concentration by 5.8%, without compromising dry matter digestibility (DMD) of either maize silage or grain concentrates. There were no significant effects of O₃ treatment on VFA production or pH. Ozone treatment reduced the relative abundance of methanogens, particularly Methanomicrobium. This study demonstrates the potential use of O₃ as a method to reduce ruminant enteric methanogenesis.