Rumen fermentation and microbial community composition influenced by live Enterococcus faecium supplementation

Ruminal microbial responses to Moringa oleifera feed in lactating goats (Capra hircus): A metagenomic exploration

The purpose of the current study was to explore the effects of Moringa oleifera feed on the taxonomy and function of the rumen microbial community, and further to evaluate its impact on milk yield and body weight in lactating goats. Nineteen goats were divided into moringa leaf diet (ML; n = 10) and masoor straw (MS; n = 9) groups. For each group fortnight milk yield and body weight was recorded. Rumen solid and liquid fraction samples were processed for metagenomic shotgun sequencing and further analysed. The pairwise comparison between the two groups showed a significant increase (p-value- <0.01) in milk yield of the ML goats after the 4th fortnight interval onwards. The metagenomic analysis revealed Bacteroidetes and Firmicutes are the most abundant phyla, with increased Bacteroidetes in response to the moringa diet. The ML group exhibited a reduction in microbial diversity, with an increase in Prevetolla and Bacteroidales populations which are positively associated with carbohydrate, protein, and VFA metabolism, and an increased proportions of Treponema sp., Ruminococcus sp., Ruminobacter amylophilus, and Aeromonas, indicating improved cellulose and nitrogen metabolism. KEGG analysis revealed significant changes in microbial gene pool and metabolic pathways, particularly in carbohydrate metabolism, propanoate metabolism, and fatty acid synthesis genes. These microbial and functional shifts are correlated with improvements in milk yield, growth rates, and potentially reduced methane emissions.This study highlighted the potential benefits of feeding moringa in the animal production system. However, furthermore experimental evidence including genetic and environmental effects is needed for a comprehensive understanding of moringa feed's impact on goat health and productivity.

Effects of peripartal rumen-derived direct-fed microbial supplementation on lactation performance, metabolism, ruminal fermentation, and microbial abundance in dairy cows

The objective of this study was to evaluate the effects of a rumen-derived direct-fed microbial (DFM) product on performance, blood biomarkers, ruminal fermentation, and bacterial abundance in dairy cows during the transition period until 100 DIM. Fifty-six Holstein cows were enrolled in a randomized complete block design from -21 to 100 DIM. Cows were blocked based on expected calving date, parity, and previous lactation milk yield for multiparous cows or genetic merit for primiparous cows. At -21 DIM, cows were randomly assigned to either a basal control diet supplemented with 150 g/d ground corn (CON; n = 29) or the control diet supplemented with ground corn plus a rumen-derived DFM product (GF; n = 27, 150 g/d ground corn + 5g/d of Galaxis Frontier [Native Microbials, San Diego, CA]; Clostridium beijerinckii at 1.0 × 107 cfu; Pichia kudriavzevii at 1.0 × 108 cfu; Ruminococcus bovis at 1.0 × 108 cfu; Butyrivibrio fibrisolvens at 1.0 × 108 cfu) that was top-dressed once a day. All cows received the same basal close-up diet from -21 DIM until calving (1.56 Mcal/kg DM and 14.46% CP) and the same lactation diet from calving to 100 DIM (1.76 Mcal/kg DM and 15.69% CP). We collected blood samples to measure biomarkers of metabolism, inflammation, and oxidative stress, as well as rumen fluid via esophageal tubing for ammonia, VFA, and microbial abundance from a subset of multiparous cows (n = 12/treatment) at various time points from -22 to 100 DIM. Compared with CON, GF cows produced more milk (+4.1 kg/d) during the postfresh period (6-14 wk). However, GF cows tended to produce more milk (+2.9 kg/d) than CON during the entire trial (0-14 wk). Although DMI was not affected by treatment, GF cows had greater feed efficiency (+0.18, milk/DMI) in the postfresh period. Compared with CON, GF cows had lower blood plasma glucose and higher BHB. Blood biomarkers showed greater concentrations of ceruloplasmin, haptoglobin, and reactive oxygen metabolites (ROM) in GF cows compared with CON. Compared with CON, GF cows had greater ruminal molar proportions of butyrate and tended to have greater valerate and lower acetate. These changes in ruminal VFA were coupled with alterations in ruminal microbial abundance, where compared with CON, GF cows tended to have a greater abundance of lactate-utilizing species (Megasphaera elsdenii), but lower abundance of cellulose-utilizing species (Fibrobacter succinogenes). Although greater ROM was accompanied by a mild inflammatory condition in GF cows, this was not detrimental to milk yield and DMI. Overall, our results suggest that supplementing GF in the transition period until 100 DIM positively affects lactation performance.

Effects of Saccharomyces cerevisiae and Bacillus subtilis on in vitro fermentation in the rumen of Hu sheep

BACKGROUND

The demand for animal products is increasing in developing countries due to population growth. However, livestock production contributes significantly to global warming, accounting for 25%. Probiotics can help improve livestock efficiency by enhancing gut microbes and fat metabolism. They can modify rumen populations, enhance fermentation, reduce methane emissions and improve feed digestion. In this study, the goal was to determine the most effective method of reducing methane emissions in the rumen of sheep in vitro by adding different concentrations of Saccharomyces cerevisiae and Bacillus subtilis.

RESULTS

Adding 8 × 106 CFU g-1 S. cerevisiae during fermentation reduced pH levels after 48 h. This also increased the concentrations of NH3-N, microbial protein and total gas production. At the same time, it decreased methane emissions. Furthermore, adding 20 × 106 CFU g-1 B. subtilis to the mixture increased total gas production (TGP) and methane production, with the highest production observed after 48 h. However, it did not affect pH levels after 48 h.

CONCLUSION

It can be concluded that S. cerevisiae had significantly increased microbial protein and NH3-N concentrations after fermentation without altering pH. Additionally, the addition of S. cerevisiae enhanced TGP and reduced methane emissions. It is worth noting that TGP increased because B. subtilis was added at a concentration of 20 × 106 CFU g-1, with no significant differences between concentrations. Therefore, we recommend adding S. cerevisiae and B. subtilis to the diet at doses of 8 and 20 × 106 CFU g-1, as it resulted in higher TGP and reduced methane emissions. © 2024 Society of Chemical Industry.

Saccharomyces cerevisiae and Kluyveromyces marxianus yeast co-cultures modulate the ruminal microbiome and metabolite availability to enhance rumen barrier function and growth performance in weaned lambs

In lambs, weaning imposes stress that can contribute to impaired rumen epithelial barrier functionality and immunological dysregulation. In this study, the effects of a yeast co-culture consisting of Saccharomyces cerevisiae and Kluyveromyces marxianus (NM) on rumen health in lambs was evaluated, with a focus on parameters including growth performance, ruminal fermentation, and epithelial barrier integrity, ruminal metabolic function, and the composition of the ruminal bacteria. In total, 24 lambs were grouped into four groups of six lambs including a control (C) group fed a basal diet, and N, M, and NM groups in which lambs were fed the basal diet respectively supplemented with S. cerevisiae yeast cultures (30 g/d per head), K. marxianus yeast cultures (30 g/d per head), and co-cultures of both yeasts (30 g/d per head), the experiment lasted for 42 d. Subsequent analyses revealed that relative to the C group, the average daily gain (ADG) of lambs in the NM group was significantly greater and exhibited significant increases in a range of mRNA relative expression including monocarboxylate transporter 1 (MCT1), (Na+)/hydrogen (H+) exchanger 1 (NHE1), (Na+)/hydrogen (H+) exchanger 3 (NHE3), proton-coupled amino acid transporter 1 (PAT1), vacuolar H+-ATPase (vH+ ATPase), claudin-1, occludin in the rumen epithelium (P < 0.05). Compared with the C group, the pH of the rumen contents in the NM group was significantly decreased , and the concentrations of acetate, propionate, and butyrate were significantly increased (P < 0.05). Analysis of the rumen bacteria showed that the NM group exhibited increases in the relative abundance of Prevotella, Treponema, Moryella, Fibrobacter, CF231 and Ruminococcus (P < 0.05). Metabolomics analyses revealed an increase in the relative content of phthalic acid and cinnamaldehyde in the NM group as compared to the C group (P < 0.05), together with the greater relative content of L-tyrosine, L-dopa, rosmarinic acid, and tyrosol generated by the tyrosine metabolic pathway (P < 0.05). Spearman's correlation analyses revealed relative abundance levels of Fibrobacter and Ruminococcus were positively correlated with the mRNA relative expression levels of PAT1, NHE3, and zonula occluden-1 (ZO-1), as well as with tyrosol, phthalic acid, and cinnamaldehyde levels (P < 0.05). Ultimately, these results suggest that dietary supplementation with NM has a wide range of beneficial effects on weaned lambs and is superior to single bacterial fermentation. These effects include improvements in daily gain and rumen epithelial barrier integrity, as well as improvements in the composition of the rumen microbiome, and alterations in tyrosine metabolic pathways.

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.

Exploring rumen fermentation and microbial populations in Dhofari goats fed a chitosan-added diet

The use of chitosan (CHI) in ruminant diets is a promising natural modifier for rumen fermentation, capable of modulating both the rumen pattern and microbial activities. The objective of this study was to explore the rumen fermentation and microbial populations in Dhofari goats fed a diet supplemented with CHI. A total of 24 Dhofari lactating goats (body weight, 27.32 ± 1.80 kg) were assigned randomly into three experimental groups (n = 8 ewes/group). Goats were fed a basal diet with either 0 (control), 180 (low), or 360 (high) mg CHI/kg of dietary dry matter (DM) for 45 days. Feeding high CHI linearly increased (p < 0.05) the propionate level and reduced the acetate, butyrate, and total protozoa count (p < 0.05). Ruminal ammonia nitrogen (NH3-N) concentrations and the acetate:propionate ratio decreased linearly when goats were fed CHI (p < 0.05). The abundances of both Spirochetes and Fibrobacteres phyla were reduced (p < 0.05) with both CHI doses relative to the control. Both low and high CHI reduced (p < 0.05) the relative abundances of Butyrivibrio hungatei, Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens, Selenomonas ruminantium and Neocallimastix californiae populations. Adding CHI significantly decreased (p < 0.05) the abundances of Ascomycota, Basidiomycota, and Bacillariophyta phyla compared to the control. Adding CHI to the diet reduces the abundance of fibrolytic-degrading bacteria, however, it increases the amylolytic-degrading bacteria. Application of 360 mg of CHI/kg DM modified the relative populations of ruminal microbes, which could enhance the rumen fermentation patterns in Dhofari goats.

Feed characteristics and potential effects on ruminal bacteria of ensiled sugar kelp and winged kelp for Holstein dairy cows

Seaweed silage has potential as an alternative feed ingredient for dairy cows. This study aims to investigate seaweed's and seaweed silageś nutrient digestibility as well as their impact on the ruminal bacterial composition. The cultivated S. latissima and A. esculenta were preserved by freezing at - 40 °C or ensiling (16 °C, 3 months) with four different treatments: no additives, 4 g formic acid/kg wet seaweed, lactic acid bacteria (LAB) inoculant, and LAB inoculant in prewilted biomass (ca. 300 g DM/kg wet biomass). The nutrient digestibility was estimated using standard feed evaluation methods. The bacterial composition in ruminal fluid after 48 h in vitro anaerobic incubation with seaweeds and common feedstuffs was analysed using 16S ribosomal RNA (rRNA) amplicon sequencing (V3-V4) and quantitative PCR (qPCR). The results suggest that S. latissima was more digestible than A. esculenta and that the preservation treatments had only a small effect on the nutrient digestibility and ruminal bacteria compositions. The rumen DM degradability of S. latissima was comparable to common perennial and corn forage; however, the total tract CP digestibility of S. latissima (460 g/kg CP) was lower than common forages (620 - 820 g/kg CP) and was not improved by ensiling. There was a lack of insoluble but rumen-degradable CP in A. esculenta, making it unsuitable as a nutrient ingredient for dairy cows. The ruminal bacterial composition changed depending on the seaweed species used as substrate: The dominant bacterial taxa when incubated with S. latissima belonged to the genus Prevotella (relative abundance: 79 - 93%), known for its ability to degrade polysaccharides in various ecosystems. Moreover, the fibrolytic bacteria including Fibrobacter succinogenes and Ruminococcus flavefaciens were > 2.5 Log2FoldChange higher when incubating with S. latissima than with A. esculenta. These bacterial taxa may play an important role in the in vitro organic matter digestibility, noted as 2 times higher in S. latissima compared to A. esculenta. The qPCR results indicated potential methane mitigation properties of the studied seaweed species, with significantly lower gene copies of Archaea 16S rRNA and methyl coenzyme-M reductase subunit A genes when the ruminal fluid was incubated with the seaweed substrates. Our study suggested that ensiled S. latissima biomass can be included in the diet of dairy cows as an alternative forage-like ingredient with the potential of methane mitigation.

Performance responses of lactating Rahmani ewes fed diet supplemented with Enterococcus faecium NRC-3 or Lactobacillus rhamnosus

Production of new types of probiotics for animal nutrition mainly depends on the appropriate bacterial strain and efficient substrate. Therefore, this study aimed to evaluate the impact of two probiotic strains containing 1.2 × 108 (CFU/g), produced on permeate media on performance responses of Rahmani ewes. Thirty early lactating ewes (about 2-3 years old and weighting on average 43.2 ± 0.3 kg) were randomly divided into three groups of 10 animals each using a completely randomized design. The 1st group was fed the basal diet (60% concentrate feed mixture (CFM) + 30% Egyptian clover + 10% bean straw). While the ewes in 2nd and 3rd groups were fed the basal diet + 2 g of Enterococcus faecium NRC-3(EF) and Lactobacillus rhamnosus (LR), respectively for 9 weeks. Ewes' diet supplementation with EF or LR increased (p < 0.05) dry matter, organic matter, crude protein, neutral detergent fiber, acid detergent fiber, and non-structural carbohydrates digestibility compared to ewes of the control group. Glucose, total protein, and albumin concentrations significantly increased in the blood of EF ewes than those of LR and control. Probiotics increased ewes' milk yield as well as milk protein, fat, and lactose yields, but no differences were observed between treatments when milk components were expressed as percentage. Milk fatty acids profile not changed due to EF or LR supplementation. Probiotics (E. faecium and L. rhamnosus) produced on cheese industry waste (permeate) have proven their ability to improve the productive performance of the lactating Rahmani ewes.

The isolation of rumen enterococci strains along with high potential utilizing cyanide

Cyanogenic glycosides in forage species and the possibility of cyanide (CN) poisoning can have undesirable effects on ruminants. The literature estimates that unknown rumen bacteria with rhodanese activity are key factors in the animal detoxification of cyanogenic glycosides, as they are capable of transforming CN into the less toxic thiocyanate. Therefore, identifying these bacteria will enhance our understanding of how to improve animal health with this natural CN detoxification process. In this study, a rhodanese activity screening assay revealed 6 of 44 candidate rumen bacterial strains isolated from domestic buffalo, dairy cattle, and beef cattle, each with a different colony morphology. These strains were identified as belonging to the species Enterococcus faecium and E. gallinarum by 16S ribosomal DNA sequence analysis. A CN-thiocyanate transformation assay showed that the thiocyanate formation capacity of the strains after a 12 h incubation ranged from 4.42 to 25.49 mg hydrogen CN equivalent/L. In addition, thiocyanate degradation resulted in the production of ammonia nitrogen and acetic acid in different strains. This study showed that certain strains of enterococci substantially contribute to CN metabolism in ruminants. Our results may serve as a starting point for research aimed at improving ruminant production systems in relation to CN metabolism.

16S rRNA Gene Amplicon Sequencing of Gut Microbiota Affected by Four Probiotic Strains in Mice

Probiotics, also referred to as "living microorganisms," are mostly present in the genitals and the guts of animals. They can increase an animal's immunity, aid in digestion and absorption, control gut microbiota, protect against sickness, and even fight cancer. However, the differences in the effects of different types of probiotics on host gut microbiota composition are still unclear. In this study, 21-day-old specific pathogen-free (SPF) mice were gavaged with Lactobacillus acidophilus (La), Lactiplantibacillus plantarum (Lp), Bacillus subtilis (Bs), Enterococcus faecalis (Ef), LB broth medium, and MRS broth medium. We sequenced 16S rRNA from fecal samples from each group 14 d after gavaging. According to the results, there were significant differences among the six groups of samples in Firmicutes, Bacteroidetes, Proteobacteria, Bacteroidetes, Actinobacteria, and Desferribacter (p < 0.01) at the phylum level. Lactobacillus, Erysipelaceae Clostridium, Bacteroides, Brautella, Trichospiraceae Clostridium, Verummicroaceae Ruminococcus, Ruminococcus, Prevotella, Shigella, and Clostridium Clostridium differed significantly at the genus level (p < 0.01). Four kinds of probiotic changes in the composition and structure of the gut microbiota in mice were observed, but they did not cause changes in the diversity of the gut microbiota. In conclusion, the use of different probiotics resulted in different changes in the gut microbiota of the mice, including genera that some probiotics decreased and genera that some pathogens increased. According to the results of this study, different probiotic strains have different effects on the gut microbiota of mice, which may provide new ideas for the mechanism of action and application of microecological agents.

Enteric Methane Emission, Rumen Fermentation and Microbial Profiles of Meat-Master Lambs Supplemented with Barley Fodder Sprouts

This study evaluated the effects of barley sprout on the ruminal fermentation characteristics, enteric methane emission and microbiome profiles of meat-master lambs. Twelve uncastrated lambs aged 3 months were used. They were randomly assigned to three dietary treatments: Eragrostis curvula hay as a control diet (T1), grass hay plus 25% barley sprouts (T2) and grass hay plus 50% barley sprouts (T3). Animals were fed the diet for 61 days, including 10 days of adaptation. Four animals per treatment were used to collect methane and rumen fluid. Methane emission was recorded for nine consecutive days, from day 52 to 60, using a hand-held laser detector. Rumen fluid was collected on day 61 using an esophageal stomach tube for volatile fatty acid and DNA sequencing. The sprout supplementation had significant (p < 0.05) effects on methane emission and ruminal fermentation. Significant effects on rumen fermentation were observed with regards to ammonia–nitrogen (NH3-N), acetic acid and a tendency (p < 0.0536) to increase propionic acid. Barley sprouts reduced methane gas emission, ammonia–nitrogen and the enhanced body weight of the animals. The bacteria Bacteroidota and Firmicutes were predominant among the identified phyla. In addition, there was a shift in the relative abundance of phylum among the treatments. The principal coordinate analysis showed a clear difference in microbiome among animals in T1 and those in T2 and T3. The sprout supplementation improves feed utilization efficiency by the animals. In conclusion, barley sprouts may be strategically used as a climate-smart feed resource for ruminants.

Antimicrobial resistance determinants in silage

Animal products may play a role in developing and spreading antimicrobial resistance in several ways. On the one hand, residues of antibiotics not adequately used in animal farming can enter the human body via food. However, resistant bacteria may also be present in animal products, which can transfer the antimicrobial resistance genes (ARG) to the bacteria in the consumer's body by horizontal gene transfer. As previous studies have shown that fermented foods have a meaningful ARG content, it is indicated that such genes may also be present in silage used as mass feed in the cattle sector. In our study, we aspired to answer what ARGs occur in silage and what mobility characteristics they have? For this purpose, we have analyzed bioinformatically 52 freely available deep sequenced silage samples from shotgun metagenome next-generation sequencing. A total of 16 perfect matched ARGs occurred 54 times in the samples. More than half of these ARGs are mobile because they can be linked to integrative mobile genetic elements, prophages or plasmids. Our results point to a neglected but substantial ARG source in the food chain.

Integration of Multiplied Omics, a Step Forward in Systematic Dairy Research

Due to their unique multi-gastric digestion system highly adapted for rumination, dairy livestock has complicated physiology different from monogastric animals. However, the microbiome-based mechanism of the digestion system is congenial for biology approaches. Different omics and their integration have been widely applied in the dairy sciences since the previous decade for investigating their physiology, pathology, and the development of feed and management protocols. The rumen microbiome can digest dietary components into utilizable sugars, proteins, and volatile fatty acids, contributing to the energy intake and feed efficiency of dairy animals, which has become one target of the basis for omics applications in dairy science. Rumen, liver, and mammary gland are also frequently targeted in omics because of their crucial impact on dairy animals’ energy metabolism, production performance, and health status. The application of omics has made outstanding contributions to a more profound understanding of the physiology, etiology, and optimizing the management strategy of dairy animals, while the multi-omics method could draw information of different levels and organs together, providing an unprecedented broad scope on traits of dairy animals. This article reviewed recent omics and multi-omics researches on physiology, feeding, and pathology on dairy animals and also performed the potential of multi-omics on systematic dairy research.

Whole genome sequence analyses-based assessment of virulence potential and antimicrobial susceptibilities and resistance of Enterococcus faecium strains isolated from commercial swine and cattle probiotic products

Enterococcus faecium is one of the more commonly used bacterial species as a probiotic in animals. The organism, a common inhabitant of the gut of animals and humans, is a major nosocomial pathogen responsible for a variety infections in humans and sporadic infections in animals. In swine and cattle, E. faecium-based probiotic products are used for growth promotion and gut functional and health benefits. The objective of this study was to utilize whole genome sequence-based analysis to assess virulence potential, detect antimicrobial resistance genes, and analyze phylogenetic relationships of E. faecium strains from commercial swine and cattle probiotics. Genomic DNA extracted from E. faecium strains, isolated from commercial probiotic products of swine (n = 9) and cattle (n = 13), were sequenced in an Illumina MiSeq platform and analyzed. Seven of the nine swine strains and seven of the 13 cattle strains were identified as Enterococcus lactis, and not as E. faecium. None of the 22 probiotic strains carried major virulence genes required to initiate infections, but many carried genes involved in adhesion to host cells, which may benefit the probiotic strains to colonize and persist in the gut. Strains also carried genes encoding resistance to a few medically important antibiotics, which included aminoglycosides [aac(6')-Ii, aph(3')-III, ant(6)-Ia], macrolide, lincosamide and streptogramin B (msrC), tetracyclines [tet(L) and tet(M)], and phenicols [cat-(pc194)]. The comparison of the genotypic to phentypic AMR data showed presence of both related and unrelated genes in the probiotic strains. Swine and cattle probiotic E. faecium strains belonged to diverse sequence types. Phylogenetic analysis of the probiotic strains, and strains of human (n = 29), swine (n = 4), and cattle (n = 4) origin, downloaded from GenBank, indicated close clustering of strains belonging to the same species and source, but a few swine and cattle probiotic strains clustered closely with other cattle and human fecal strains. In conclusion, the absence of major virulence genes characteristic of the clinical E. faecium strains suggests that these probiotic strains are unlikely to initiate opportunistic infection. However, the carriage of AMR genes to medically important antibiotics and close clustering of the probiotic strains with other human and cattle fecal strains suggests that probiotic strains may pose risk to serve as a source of transmitting AMR genes to other gut bacteria.

Draft Genome Sequences of Two Strains of Enterococcus lactis Showing High Potential as Cattle Probiotic Supplements

Probiotic supplements are currently widely used in cattle feeding practices. However, knowledge regarding the genomic landscape of cattle probiotic microorganisms is relatively scarce and is based on analogies with human probiotics. Here, we report on the draft genome sequences of two Enterococcus lactis strains, VKPM B-4989 and VKPM B-4992, which were isolated from the rumen of a healthy calf and utilized as a probiotic additive.

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.

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.

Transformation of bacterial community structure in rumen liquid anaerobic digestion of rice straw

Rumen liquid can effectively degrade lignocellulosic biomass, in which rumen microorganisms play an important role. In this study, transformation of bacterial community structure in rumen liquid anaerobic digestion of rice straw was explored. Results showed that rice straw was efficiently hydrolyzed and acidified, and the degradation efficiency of cellulose, hemicellulose and lignin reached 46.2%, 60.4%, and 12.9%, respectively. The concentration of soluble chemical oxygen demand (SCOD) and total volatile fatty acid (VFA) reached 12.9 and 8.04 g L^-1. The high-throughput sequencing results showed that structure of rumen bacterial community significantly changed in anaerobic digestion. The Shannon diversity index showed that rumen bacterial diversity decreased by 32.8% on the 5th day of anaerobic digestion. The relative abundance of Prevotella and Fibrobacter significantly increased, while Ruminococcus significantly decreased at the genus level. The Spearman correlation heatmap showed that pH and VFA were the critical factors affecting the rumen bacterial community structure. The function prediction found that rumen bacteria mainly functioned in carbohydrate transport and metabolism, which might contain a large number of lignocellulose degrading enzyme genes. These studies are conducive to the better application of rumen microorganisms in the degradation of lignocellulosic biomass.

Metataxonomic profiling of bacterial communities and their predictive functional profiles in traditionally preserved meat products of Sikkim state in India

Traditionally preserved meat products are common food items in Sikkim state of India. We studied the high-throughput sequencing of four traditionally preserved meat products viz. beef kargyong, pork kargyong, yak satchu and khyopeh to profile the bacterial communities and also inferred their predictive functional profiles. Overall abundant OTUs in samples showed that Firmicutes was the abundant phylum followed by Proteobacteria and Bacteroidetes. Abundant species detected in each product were Psychrobacter pulmonis in beef kargyong, Lactobacillus sakei in pork kargyong, Bdellovibrio bacteriovorus and Ignatzschinera sp. in yak satchu and Lactobacillus sakei and Enterococcus sp. in khyopeh. Several genera unique to each product, based on analysis of shared OTUs contents, were observed among the samples except in khyopeh. Goods coverage recorded to 1.0 was observed, which reflected the maximum bacterial diversity in the samples. Alpha diversity metrics showed a maximum bacterial diversity in khyopeh and lowest in pork kargyong Community dissimilarities in the products were observed by PCoA plot. A total of 133 KEGG predictive functional pathways was observed in beef kargyong, 131 in pork kargyong, 125 in yak satchu and 101 in khyopeh. Metagenome contribution of the OTUs was computed using PICTRUSt2 and visualized by BURRITO software to predict the metabolic pathways. Several predictive functional profiles were contributed by abundant OTUs represented by Enterococcus, Acinetobacter, Agrobacterium, Bdellovibrio, Chryseobacterium, Lactococcus, Leuconostoc, Psychrobacter, and Staphylococcus.

Effect of microbial feed additives on growth performance, microbial protein synthesis, and rumen microbial population in growing lambs

Arabi lambs (n =28; body weight = 24 ± 3.7 kg; average age = 120 ± 8 days) were used to investigate the effect of microbial additives on growth performance, microbial protein synthesis and rumen microbial population of fattening lamb based on completely randomized design. Four treatments were studied: (1) control (without additive; CON); (2) Lactobacillus fermentum and L. plantarum (FP); (3) Saccharomyces cerevisiae (SC) plus FP (SCFP); and (4) Megasphaera elsdenii plus SCFP (MSCFP). Lambs were inoculated before morning feeding (daily oral dosed) with a 50 mL microbial suspension as follows: FP, 50 mL bacterial suspension containing 4.5 × 10⁸ colony-forming unit per day (cfu/d) of L. plantarum and L. fermentum (in ratio 50:50); SCFP, 50 mL microbial suspension containing 4.5 × 10⁸ cfu/d FP and 1.4 × 10¹⁰ cfu/d SC; MSCFP, 50 mL microbial suspension containing 4.5 × 10⁸ cfu/d Me, 4.5 × 10⁸ cfu/d FP and 1.4 × 10¹⁰ cfu/d SC. Feed intake and body weight of lambs were not affected by microbial additives. Average daily gain and feed efficiency were increased on day 0 to 21. The highest concentration of uric acid, total excreted purine derivatives (PD), microbial N, microbial CP, and metabolizable protein were in MSCFP lambs. The ruminal population of Ruminococcus albus and Ruminococcus flavefaciens was higher in MSCFP and SCFP than CON and FP lambs. The highest and the lowest abundance of M. elsdenii and methanogen respectively was observed in lambs fed on microbial additives. The tendency to improve growth performance vs. CON may be due to improvements in microbial protein synthesis and microbial populations, especially fiber-degrading bacteria. The decrease in the population of methanogens as a result of the use of microbial additives is another positive result.

Influence of probiotics on biofilm formation and diversity of bacteria colonising crop sorghum ensiled with unsalable vegetables

The objective of this study was to characterise in situ digestion kinetics and bacterial colonisation of crop sorghum ensiled with unsalable carrot or pumpkin at 0, 20 or 40% dry matter (DM). Silages with or without the application of a commercial probiotic were incubated in situ for 0, 3, 6, 9, 24 and 48 h. Calculation of in situ digestion kinetics was conducted for DM, organic matter and neutral detergent fibre (aNDF). The V4 region of the 16S rRNA gene was sequenced to determine the composition and diversity of bacteria colonising the silage. Organic matter and DM digestion kinetics indicated that greater vegetable inclusion increased (P < 0.05) the soluble fraction and effective degradability. Bacterial richness at 48 h incubation was greater (P = 0.02) in 20% carrot and 40% pumpkin treatments, compared with the control. An effect of level × probiotic was observed with increased Shannon diversity (P = 0.01) for 40% carrot and 20% pumpkin probiotic treatments, respectively. Primary colonising bacteria were members of the Prevotella genus, dominating after 3 and 6 h of incubation. The abundance of Prevotella increased by 4.1% at 3 h (P < 0.01) and by 4.7% at 9 h incubation with probiotics, compared with the control. Secondary biofilm colonisers included members of Treponema, Saccharofermentans, Fibrobacter, Ruminobacter and Anaerosporobacter genera, dominant from 9 h incubation onward. This study demonstrated that including unsalable vegetables at 20 or 40% DM increases the soluble fraction and effective degradability of sorghum silage during in situ digestion and increases diversity of bacteria colonising ensiled vegetables within the rumen. KEY POINTS: • Ensiling unsalable vegetables is a viable strategy to reduce food waste. • Ensiled vegetables increased in situ soluble fraction and effective degradability. • Bacterial richness at 48 h incubation improved with 20% carrot or 40% pumpkin. • Diversity of colonising rumen bacteria increased with carrot or pumpkin inclusion.

Impact of Fermented Corn-Soybean Meal on Gene Expression of Immunity in the Blood, Level of Secretory Immunoglobulin A, and Mucosa-Associated Bacterial Community in the Intestine of Grower-Finisher Pigs

This study was conducted to determine the effect of a fermented corn–soybean meal [fermented feed (FF)] on the gene expression of immunity in the blood, the level of secretory immunoglobulin A (sIgA), and mucosa-associated bacterial community in the duodenum and colon of grower-finisher pigs. In this study, crossbred barrows (Duroc × Landrace × Large White) were randomly assigned to either an unfermented corn–soybean diet (Ctrl) (n = 6) or an FF diet (n = 6), and then the following were examined: the expression of immunity using real-time reverse transcription polymerase-chain reaction in the blood, sIgA using enzyme-linked immunosorbent assay (ELISA), and changes in the bacterial community using Illumina Hiseq sequencing in the mucosa of the duodenum and colon. Compared with control pigs fed with a standard diet, the results showed that FF caused upregulation of the mRNA expression of Toll-like receptor 3 (TLR3), TLR4, TLR6, and TLR8 in the blood (P < 0.05). Moreover, sequencing of 16S rRNA genes in duodenal mucosa samples indicated that the FF diet had a lower proportion of Tenericutes (P < 0.05) in the duodenal mucosa-associated microbiota, and FF significantly increased the percentage of Rikenellaceae and Christensenellaceae but decreased the abundance of Lachnospiraceae (P < 0.05) in the colonic mucosa-associated microbiota. The ELISA results showed that FF significantly increased the concentration of sIgA in the colonic mucosa (P < 0.05). More importantly, our correlation analysis indicated that the gene expression of immunity in the blood and the concentration of sIgA was associated with colonic mucosa-associated microbiota. Our data provide new knowledge into the adaptation response of the intestine to fermented feeding in monogastric animals.