Time of Day for Harvest Affects the Fermentation Parameters, Bacterial Community, and Metabolic Characteristics of Sorghum-Sudangrass Hybrid Silage

Cleaner anaerobic fermentation and greenhouse gas reduction of crop straw

Rice anaerobic fermentation is a significant source of greenhouse gas (GHG) emissions, and in order to efficiently utilize crop residue resources to reduce GHG emissions, rice straw anaerobic fermentation was regulated using lactic acid bacteria (LAB) inoculants (FG1 and TH14), grass medium (GM) to culture LAB, and Acremonim cellulolyticus (AC). Microbial community, GHG emission, dry matter (DM) loss, and anaerobic fermentation were analyzed using PacBio single-molecule real-time and anaerobic fermentation system. The epiphytic microbial diversity of fresh rice straw was extremely rich and contained certain nutrients and minerals. During ensiling, large amounts of GHG such as carbon dioxide are produced due to plant respiration, enzymatic hydrolysis reactions, and proliferation of aerobic bacteria, resulting in energy and DM loss. Addition of FG1, TH14, and AC alone improved anaerobic fermentation by decreasing pH and ammonia nitrogen content (P < 0.05) and increased lactic acid content (P < 0.05) when compared to the control, and GM showed the same additive effect as LAB inoculants. Microbial additives formed a co-occurrence microbial network system dominated by LAB, enhanced the biosynthesis of secondary metabolites, diversified the microbial metabolic environment and carbohydrate metabolic pathways, weakened the amino acid metabolic pathways, and made the anaerobic fermentation cleaner. This study is of great significance for the effective utilization of crop straw resources, the promotion of sustainable livestock production, and the reduction of GHG emissions.IMPORTANCETo effectively utilize crop by-product resources, we applied microbial additives to silage fermentation of fresh rice straw. Fresh rice straw is extremely rich in microbial diversity, which was significantly reduced after silage fermentation, and its nutrients were well preserved. Silage fermentation was improved by microbial additives, where the combination of cellulase and lactic acid bacteria acted as enzyme-bacteria synergists to promote lactic acid fermentation and inhibit the proliferation of harmful bacteria, such as protein degradation and gas production, thereby reducing GHG emissions and DM losses. The microbial additives accelerated the formation of a symbiotic microbial network system dominated by lactic acid bacteria, which regulated silage fermentation and improved microbial metabolic pathways for carbohydrates and amino acids, as well as biosynthesis of secondary metabolites.

Investigating the efficacy of an exopolysaccharide (EPS)-producing strain Lactiplantibacillus plantarum L75 on oat silage fermentation at different temperatures

This study investigates the effectiveness of an exopolysaccharide (EPS)-producing strain (Lactiplantibacillus plantarum L75) alone or in combination with Saccharomyces cerevisiae on the fermentation characteristics, antioxidant capacities and microbial community successions of oat silage stored at various temperatures. A rapid decrease in pH and lactic acid accumulation was observed in silages treated with L. plantarum and S. cerevisiae (LS) as early as 3 days of ensiling (p < 0.05). Over the ensiling period of 7-60 days, L. plantarum (L)-inoculated groups showed the lowest pH, lowest ammonia nitrogen and the highest amount of lactic acid regardless of the storage temperatures. When the oat silage was stored at 15°C, LS-inoculated group exhibited a higher superoxide dismutase (SOD) activity than control and L-inoculated group. Furthermore, the proportion of Lactiplantibacillus in the combined inoculation group increased by 65.42% compared to the L-inoculated group (33.26%). Fungal community data revealed abundant Penicillium carneum in the control and L-inoculated groups stored at 15°C. Conclusively, these results showed that combined inoculation of L. plantarum L75 and S. cerevisiae improved the fermentation quality of oat silage at 15°C, thus proposing a technique for enhancing the fermentation quality of silage in regions with low temperatures during harvest season.

Antibiotic intervention exacerbated oxidative stress and inflammatory responses in SD rats under hypobaric hypoxia exposure

The gut microbiota plays a crucial role in maintaining host nutrition, metabolism, and immune homeostasis, particularly in extreme environmental conditions. However, the regulatory mechanisms of the gut microbiota in animal organisms hypobaric hypoxia exposure require further study. We conducted a research by comparing SD rats treated with an antibiotic (ABX) cocktail and untreated SD rats that were housed in a low-pressure oxygen chamber (simulating low pressure and hypoxic environment at 6000 m altitude) for 30 days. After the experiment, blood, feces, and lung tissues from SD rats were collected for analysis of blood, 16S rRNA amplicon sequencing, and non-targeted metabolomics. The results demonstrated that the antibiotic cocktail-treated SD rats exhibited elevated counts of neutrophil (Neu) and monocyte (Mon) cells, an enrichment of sulfate-reducing bacteria (SBC), reduced levels of glutathione, and accumulated phospholipid compounds. Notably, the accumulation of phospholipid compounds, particularly lysophosphatidic acid (LPA), lipopolysaccharide (LPS), and lysophosphatidylcholine (LPC), along with the aforementioned changes, contributed to heightened oxidative stress and inflammation in the organism. In addition, we explored the resistance mechanisms of SD rats in low-oxygen and low-pressure environments and found that increasing the quantity of the Prevotellaceae and related beneficial bacteria (especially Lactobacillus) could reduce oxidative stress and inflammation. These findings offer valuable insights into enhancing the adaptability of low-altitude animals under hypobaric hypoxia exposure.

Ensiling hybrid Pennisetum with lactic acid bacteria or organic acids improved the fermentation quality and bacterial community

The aim of this study was to compare the effect of different additives on nutritional quality, fermentation variables and microbial diversity of hybrid Pennisetum silages. A control (CK - no additives) and seven treatments were tested, namely, Lactiplantibacillus plantarum (LP), Lentilactobacillus buchneri (LB), propionic acid (PA), calcium propionate (CAP), LP + LB; LP + PA and LP + CAP. In comparison with CK, all treatments increased the contents of crude protein and lactic acid, decreased the content of butyric acid, and altered the bacterial communities of the silage. Except for the CAP and LP + CAP treatments, the additives decreased pH and the ammonia nitrogen:total nitrogen (NH₃-N:TN) ratio. The results of principal component analysis revealed that the PA, LP + PA and LP + LB treatments ranked as the top three silages. The PA and LP + PA treatments exhibited higher water-soluble carbohydrate content, but lower pH, and NH₃-N:TN ratio than the other treatments. With the PA and LP + PA treatments, the relative abundances of Lactobacillus and Enterobacter decreased, and of Proteobacteria and Delftia increased, while the carbohydrate metabolism of the microorganisms improved. The LP and LB treatments reduced the Shannon and Simpson diversities. In the beta diversity, PA and LP + PA separated from the other treatments, indicating that there were differences in the composition of bacterial species. The relative abundance of Lactobacillus increased in the LP and LB treatments and of Leucanostoc and Weissella increased in the CAP and LP + CAP treatments. In summary, the addition of L. plantarum, L. buchneri, propionic acid, calcium propionate, and their combinations improved fermentation quality, inhibited harmful bacteria and conserved the nutrients of hybrid Pennisetum.

Long transportation duration affects nutrient composition, mycotoxins and microbial community in whole-plant corn silage

Introduction

Potential nutrient losses and mycotoxin accumulation caused by abnormal fermentation during transportation from cropland to dairy farms leads to the diseases incidence and threatens the health of dairy cows, then further causes financial losses. The aim of this study was to investigate the effects of different transportation times on the nutritional composition, mycotoxins, and microbial communities in whole-plant corn silage (WPCS).

Methods

Three groups were subjected to different transport times: DY, short (<200 min); ZY, medium time (300-500 min); and CY, long transport time (>600 min). WPCS were collected from the same field, and nutrient composition and microbial composition before and after transportation were analyzed.

Results and discussion

Our results showed that the temperature of WPCS was higher in the ZY and CY groups than in the DY group (P < 0.01). There were no significant differences in dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE) and starch contents after different transportation times (P > 0.05), whereas the starch and water-soluble carbohydrates (WSC) contents in the CY group was significantly decreased after transport (P < 0.05). Similarly, the concentration of vomitoxin in the DY and CY groups declined markedly (P < 0.05) and the zearalenone content in the DY group also significantly decreased after transportation (P < 0.05). Regarding the analysis of microorganisms in WPCS, UniFrac-distance matrices and Shannon indices showed differences in the ZY group (P < 0.05), but fungal diversities were not influenced by the transport time (P > 0.05). In the ZY group, the relative abundance of Lactiplantibacillus decreased significantly after transportation (P > 0.05), but the relative abundances of unidentified_Chloroplast, Pantoea, Gluconobacter, unidentified Acetobacter and Acinetobacter increased markedly (P < 0.05). In addition, the relative abundances of Acetobacter and Gluconobacter in the CY group increased after transport (P < 0.05). Among fungal communities, a total of three, nine, and ten different fungal flora were observed in the DY, ZY, and CY groups, respectively, although no difference was found in fungal diversity. In conclusion, increased temperature, loss of starch, and mycotoxin variation were found with increased transport time. This might be the result of competition between bacteria and fungi, and novel technologies will need to be utilized for further exploration of the mechanism.

Diurnal Variation of Epiphytic Microbiota: an Unignorable Factor Affecting the Anaerobic Fermentation Characteristics of Sorghum-Sudangrass Hybrid Silage

Forage epiphytic microbiota exhibits pronounced changes in composition and function throughout the day. However, the effects of these changes on silage fermentation are rarely explored. Here, we transplanted the epiphytic microbiota of sorghum-sudangrass hybrid (SSG) harvested at 7:00 h (AM), 12:00 h (M), and 17:00 h (PM) to sterilized SSG to evaluate the effects of diurnal variation of epiphytic microbiota on fermentation characteristics. During fermentation, remarkable differences in bacterial community successions were observed between silages inoculated with AM and M microbiota. Compared to AM microbiota, M microbiota inoculation increased the proportions of Pantoea dispersa, Leuconostoc lactis, Enterobacter, and Klebsiella variicola, whereas it decreased the proportions of Weissella cibaria and Lactobacillus plantarum during fermentation. This led to the most rapid pH declines and organic acid production in AM silage and the slowest in M silage. Both M and PM microbiota affected the bacterial cooccurrence patterns, indicated by decreased complexity and stability in the community structures of M and PM silages compared to that of AM silage. The predicted functions indicated that some key carbohydrate metabolism pathways related to lactic acid synthesis were downregulated, while some competing pathways (ascorbate and aldarate metabolism and C5-branched dibasic acid metabolism) were upregulated in M silage compared to AM silage after 3 days of fermentation. Correlation analysis revealed positive correlations between competing pathways and enterobacterial species. The current study highlights the importance of diurnal variation of epiphytic microbiota in affecting the silage bacterial community, potentially providing an effective strategy to improve silage quality by optimizing harvest time. IMPORTANCE Ensiling is a way to preserve wet biomass for animal and bioenergy production worldwide. The fermentation quality of silage is largely dependent on the epiphytic microbiota of the material. Plant epiphytic microbiota exhibit diurnal changes in composition and function. However, the effects of these changes on silage fermentation are rarely explored. The results presented here demonstrated that diurnal variation of epiphytic microbiota could affect the fermentation characteristics and bacterial community during SSG fermentation. Marked bacterial community differences were observed between AM and M silages during the initial 3 days of fermentation. The dominance rate of Lactobacillus plantarum was highest in AM silage, whereas enterobacterial species were more abundant in M silage. The predicted function revealed downregulated lactic acid synthesis pathways and upregulated competing pathways in M silage compared to those in AM silage. This study provides clues for technological-parameter optimization of the fermentation process by the selection of harvest time.

Evaluating the fermentation characteristics, bacterial community, and predicted functional profiles of native grass ensiled with different additives

Bioaugmentation of native grass ensiling with Lactobacillus plantarum or Lactobacillus buchneri or Pediococcus pentosaceus on the ensiling performance and bacterial community was investigated after 30 days of the fermentation process. The native grass was inoculated with distilled water, Lactobacillus plantarum, Lactobacillus plantarum, and Lactobacillus buchneri, and Lactobacillus plantarum, Lactobacillus buchneri, and Pediococcus pentosaceus as the CON treatment, T1 treatment, T2 treatment, and T3 treatment, respectively. The addition of lactic acid bacteria was added at a total of 1 × 10⁶ colony-forming unit/g of fresh weight. As expected, the markedly (p < 0.05) lower water-soluble carbohydrate content was tested in the T2 and T3 treatments compared to the CON and T1 treatments. Compared to the CON and T1 treatment, significantly (p < 0.05) higher crude protein content, and lower acid detergent fiber and neutral detergent fiber contents were found in the T2 and T3 treatments. Compared to the CON treatment, the pH significantly (p < 0.05) decreased in the lactic acid bacteria (LAB) inoculated silage, and the lowest pH was measured in the T3 treatment. Similarly, significantly higher lactic acid and acetic acid contents were also found in the T3 treatment compared to those in other treatments. After 30 days of ensiling, the Shannon and Chao1 indexes in silages decreased compared to that in the fresh materials (FMs). The principal coordinate analysis indicated that both FM and silage were distinctly separated in each treatment with no interactions on the confidence ellipse (R = 0.8933, p = 0.001). At the phylum level, the dominant phylum was shifted from Proteobacteria to Firmicutes after the fermentation process. Interestingly, Weissella dominated the fermentation in the CON treatment and Lactobacillus dominated the fermentation in all inoculated LAB silages at the genus level. Results of functional prediction analyses showed that the metabolism of amino acid, cofactors, and vitamins, and membrane transport was reduced, while the metabolism of nucleotide and majority carbohydrates was increased after ensiling. The complex LAB (Lactobacillus plantarum, Lactobacillus buchneri, and Pediococcus pentosaceus) exhibited the potential possibility to decrease pH and enhance the relative abundance of LAB in response to obtaining high-quality silage by the synergistic effects. These results suggested that the complex LAB could improve the ensiling performance of native grass silage, and lay a theoretical basis for inoculant application in native grass.

Effects of laccase and lactic acid bacteria on the fermentation quality, nutrient composition, enzymatic hydrolysis, and bacterial community of alfalfa silage

Ensiling has long been as a mainstream technology of preserving forage for ruminant production. This study investigated the effects of bioaugmented ensiling with laccase and Pediococcus pentosaceus on the fermentation quality, nutritive value, enzymatic hydrolysis, and bacterial community of alfalfa. The application of laccase and Pediococcus pentosaceus combination was more potent in modulating the fermentation quality of silage than laccase and Pediococcus pentosaceus alone, as indicated by higher lactic acid contents and lactic acid to acetic acid ratios, and lower pH, dry matter losses, and ammonia nitrogen contents. Moreover, treatments with additive enhanced protein preservation and structural carbohydrate degradation, while increasing true protein and water-soluble carbohydrate contents. By promoting lignin degradation, treatments containing laccase further facilitated the release of sugars from cellulose compared with treatment with Pediococcus pentosaceus alone. The additive treatments reduced the bacterial diversity and optimized the bacterial community composition of silage, with an increase in the relative abundance of desirable Lactobacillus and a decrease in the relative abundance of undesirable Enterobacter and Klebsiella. PICRUSt functional prediction based on Kyoto Encyclopedia of Genes and Genomes (KEGG) databases revealed that PL and LPL treatments increased the metabolism of membrane transport, carbohydrate, and terpenoids and polyketides related to fermentation activities. It can be concluded that bioaugmented ensiling with laccase and Pediococcus pentosaceus combination can be an effective and practical strategy to improve silage fermentation and nutrient preservation of alfalfa silage.