Microbiome dynamics during ensiling of corn with and without Lactobacillus plantarum inoculant

Effects of cellulase or Lactobacillus plantarum on ensiling performance and bacterial community of sorghum straw

This study aimed to evaluate the effects of cellulase or Lactobacillus plantarum (L. plantarum) on the fermentation characteristics and microbial community structure of the sorghum straw silage. Sorghum straw was treated with the following four experimental conditions: distilled water (control, CK), cellulase (CEL), Lactobacillus plantarum (LP), and a combined treatment of Lactobacillus plantarum with cellulase (LPCEL). These results indicated that the LP treatment could markedly (p < 0.05) preserve the crude protein content compared to that in other treatments, whereas the CEL significantly (p < 0.05) reduced the acid detergent fiber content, while the LPCEL had the highest lactic acid content and lowest pH value. Proteobacteria and Pantoea were identified as the dominant phylum and genus in fresh materials, respectively. This phylum level dominance transitioned to Firmicutes post-treatment, while at the genus level, the community shifted from Pantoea to co-dominance of Lactobacillus and Prevotella, with Lactobacillus being the most abundant in both the CEL and LPCEL treatments. In conclusion, adding L. plantarum and cellulase to sorghum straw can significantly improve the fermentation quality of sorghum straw silage, and improve the nutritional value of silage by affecting the microbial community structure and metabolic pathways.

Ensiling characteristics, in vitro digestibility and bacterial community structure of mulberry leaf silage with or without the addition of cellulase, protease, and starch

Objective

This study aimed to investigate the effects of cellulase, protease, and starch on the fermentation quality, in vitro digestibility, and microbial community of mulberry leaf silage after 30d of ensiling.

Methods

Mulberry leaves (376 g/kg dry matter (DM)) were ensiled with four experimental treatments: i) CON, no additives; ii) CEL, added cellulase (120 U/g fresh matter [FM]); iii) CPR, added cellulase (120 U/g FM) and protease (50 U/g FM); and iv) CPS, added cellulase (120 U/g FM), protease (50 U/g FM), and starch (2% FM).

Results

All treatments with additives improved fermentation quality, showing higher DM (353 ~ 378 vs. 341 g/kg DM), lactic acid (LA) content (51.6 ~ 64.6 vs. 40.2 g/kg DM), lactic acid bacteria (LAB) counts (7.63 ~ 7.73 vs. 7.49 log10 CFU /g of FM), along with lower pH values (4.29 ~ 4.60 vs. 5.09), and DM losses (124 ~ 130 vs. 134 g/kg DM) compared to the CON group. All the additive treated groups showed higher in vitro digestibility of DM (698 ~ 720 vs. 618 g/kg DM), in vitro digestibility of NDF (395 ~ 412 vs. 336 g/kg DM), and ADF (277 ~ 298 vs. 232 g/kg DM) than CON. Among all the groups, the CPS group exhibited the highest DM content (378 g/kg DM), LA content (64.6 g/kg DM) and LAB counts (7.73 log10 CFU /g of FM), with the lowest pH value (4.29) and DM losses (124 g/kg DM). Additionally, the additive treatments increased abundance of bacteria like Firmicutes and Enteroccocus, while reducing Proteobacteria abundance, and resulted in lower diversity and richness of the microbial community. Specifically, CPR and CPS silages showed increased Pediococcus and decreased Enterobacter compared to CON and CEL, and CPS silage had a relatively high abundance of favorable Bacteroidota. Furthermore, the CPS silage exhibited upregulated genetic functions, energy and lipid metabolism, as well as metabolism of cofactors and vitamins compared to the other groups.

Conclusion

The combined application of cellulase, protease, and starch effectively improved the fermentation quality, in vitro digestibility, and microbial community of mulberry leaf silage over the 30-day ensiling period.

Effects and function of citric acid on fermentation quality and microbial community in sugarcane tops silage with high and low water-soluble carbohydrate content

Sugarcane tops silage (STS), as a source of roughage for ruminants, is rich in water-soluble carbohydrate (WSC) content, which significantly affects silage quality. Citric acid (CA) is a low-cost natural antimicrobial agent that can inhibit undesirable microbes and improve silage quality. The objectives of this study were to investigate the effects of CA on the chemical composition, fermentation quality, microbial communities, and metabolic pathways of STS with high and low WSC contents before or after aerobic exposure. Fresh sugarcane tops with low-WSC [143.05 g/kg dry matter (DM)] and high-WSC (249.99 g/kg DM) contents were treated with and without CA and then ensiled for 125 days, followed by aerobic exposure for 4, 8, and 16 days. The results showed that high-WSC STS had lower crude protein (CP) content and higher DM, neutral detergent fiber (NDF), and acid detergent fiber (ADF) contents, whether treated with CA or not. CA-inoculated silage exhibited decreased DM loss and enterobacteria (EB) counts compared to the control. High-WSC STS treated with CA had higher WSC content and lower yeast count than those without CA inoculation. During the 0-16 days of aerobic exposure, the propionic acid and butyric acid contents in CA-inoculated silage were almost unchanged and ranged from 0 to 1 g/kg DM. Meanwhile, the ethanol content was almost unchanged and ranged from 0 to 1 g/kg DM only in low-WSC STS, irrespective of CA addition. Before aerobic exposure, CA inoculation decreased the abundances of undesirable microbes (e.g., Clostridium_sensu_stricto_12 and Paecilomyces) and animal pathogens, while amino acid metabolism was lower in high-WSC STS regardless of CA treatment. After aerobic exposure, CA inoculation increased the abundance of bacteria with antibacterial effects, including Paenibacillus and Bacillus. Moreover, the metabolism of energy and nucleotides was lower in high-WSC STS treated with CA, and the animal pathogens was lower in low-WSC STS treated with CA. In conclusion, CA inoculation could be effective in decreasing nutrients loss, improving fermentation quality, inhibiting harmful microorganisms, and modulating the metabolic pathways of microorganisms in STS with high and low WSC contents prior to and after aerobic exposure.

Effects of rumen fluid and molasses on the nutrient composition, fermentation quality, and microflora of Caragana korshinskii Kom. silage

The aim of this experiment was to investigate the effects of rumen fluid and molasses on the nutrient composition, fermentation quality, and microflora of Caragana korshinskii Kom. The trial included four treatments: a control group (CK) without additives and experimental groups supplemented with 7% rumen fluid (R), 4% molasses (M), and 7% rumen fluid + 4% molasses (RM). 15 days and 60 days of ensiling. The results showed that the addition of R, M, and RM reduced the contents of neutral detergent fibre (NDF) and acid detergent fibre (ADF). The addition of M and RM increased the content of water soluble carbohydrates (WSC) but increased the loss of DM. The addition of M and RM promoted rapid pH reduction below 4.2. At 60 days of ensiling, the addition of R alone promoted the production of lactic acid (LA). The addition of R and RM increased microbial diversity. The addition of RM slowed the rate at which Lactobacillus became the dominant genus and improved the ability of Enterobacter to compete for fermentable substrates. M and RM could increase microbial activity and promote metabolism. In general, the addition of M or RM improved the fermentation quality and nutritional value of C. korshinskii silage.

Fermentation quality, amino acids profile, and microbial communities of whole-plant soybean silage in response to Lactiplantibacillus plantarum B90 alone or in combination with functional microbes

Promoting the availability of silage with a high protein content on farms can lead to profitable and sustainable ruminant production systems. Whole plant soybean (Glycine max L. Merrill, WPS) is a promising high-protein forage material for silage production. In this study, we investigated the fermentation quality, amino acids profile and microbial communities of WPS silage in response to inoculation of lactic acid bacteria (LAB) alone or in combination with non-LAB agents. Before preparing the treatments, the chopped WPS was homogenized thoroughly with 0.3% molasses (0.3 g molasses per 100 g fresh matter). The treatments included CK (sterilized water), LP (Lactiplantibacillus plantarum B90), LPBS (LP combined with Bacillus subtilis C5B1), and LPSC (LP combined with Saccharomyces cerevisiae LO-1), followed by 60 days of fermentation. The inoculants significantly decreased the bacterial diversity and increased the fungal diversity of WPS silage after ensiling. As a result, the contents of lactic acid and acetic acid increased, while the pH value and propionic acid content decreased in the inoculated silages. The amino acids profile was not influenced by inoculants except phenylalanine amino acid, but LP and LPSC silages had substantial greater (p < 0.05) relative feed values of 177.89 and 172.77, respectively, compared with other silages. Taken together, the inoculation of LP alone or in combination with BS was more effective in preserving the nutrients of WPS silage and improve fermentation quality.

Multi-omics analysis reveals the core microbiome and biomarker for nutrition degradation in alfalfa silage fermentation

Alfalfa (Medicago sativa L.) is one of the most extensively cultivated forage crops globally, and its nutritional quality critically influences the productivity of dairy cows. Silage fermentation is recognized as a crucial technique for the preservation of fresh forage, ensuring the retention of its vital nutrients. However, the detailed microbial components and their functions in silage fermentation are not fully understood. This study integrated large-scale microbial culturing with high-throughput sequencing to thoroughly examine the microbial community structure in alfalfa silage and explored the potential pathways of nutritional degradation via metagenomic analysis. The findings revealed an enriched microbial diversity in silage, indicated by the identification of amplicon sequence variants. Significantly, the large-scale culturing approach recovered a considerable number of unique microbes undetectable by high-throughput sequencing. Predominant genera, such as Lactiplantibacillus, Leuconostoc, Lentilactobacillus, Weissella, and Liquorilactobacillus, were identified based on their abundance and prevalence. Additionally, genes associated with Enterobacteriaceae were discovered, which might be involved in pathways leading to the production of ammonia-N and butyric acid. Overall, this study offers a comprehensive insight into the microbial ecology of silage fermentation and provides valuable information for leveraging microbial consortia to enhance fermentation quality.

IMPORTANCE

Silage fermentation is a microbial-driven anaerobic process that efficiently converts various substrates into nutrients readily absorbable and metabolizable by ruminant animals. This study, integrating culturomics and metagenomics, has successfully identified core microorganisms involved in silage fermentation, including those at low abundance. This discovery is crucial for the targeted cultivation of specific microorganisms to optimize fermentation processes. Furthermore, our research has uncovered signature microorganisms that play pivotal roles in nutrient metabolism, significantly advancing our understanding of the intricate relationships between microbial communities and nutrient degradation during silage fermentation.

Effects of temperature and lactic acid Bacteria additives on the quality and microbial community of wilted alfalfa silage

This study investigated the influence of different temperatures (35℃ High temperature and average indoor ambient temperature of 25℃) and lactic acid bacterial additives (Lactiplantibacillus plantarym, Lentilactobacillus buchneri, or a combination of Lactiplantibacillus plantarym and Lentilactobacillus buchneri) on the chemical composition, fermentation quality, and microbial community of alfalfa silage feed. After a 60-day ensiling period, a significant interaction between temperature and additives was observed, affecting the dry matter (DM), crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) of the silage feed (p < 0.05). Temperature had a highly significant impact on the pH value of the silage feed (p < 0.0001). However, the effect of temperature on lactic acid, acetic acid, propionic acid, and butyric acid was not significant (p > 0.05), while the inoculation of additives had a significant effect on lactic acid, acetic acid, and butyric acid (p > 0.05). As for the dynamic changes of microbial community after silage, the addition of three kinds of bacteria increased the abundance of lactobacillus. Among all treatment groups, the treatment group using complex bacteria had the best fermentation effect, indicating that the effect of complex lactic acid bacteria was better than that of single bacteria in high temperature fermentation. In summary, this study explained the effects of different temperatures and lactic acid bacterial additives on alfalfa fermentation quality and microbial community, and improved our understanding of the mechanism of alfalfa related silage at high temperatures.

Combined Effects of Lactic Acid Bacteria and Protease on the Fermentation Quality and Microbial Community during 50 Kg Soybean Meal Fermentation Simulating Actual Production Scale

The improvement in the utilization rate and nutritional value of soybean meal (SBM) represents a significant challenge in the feed industry. This study conducted a 50 kg SBM fermentation based on the 300 g small-scale fermentation of SBM in early laboratory research, to explore the combined effects of lactic acid bacteria (LAB) and acid protease on fermentation quality, chemical composition, microbial population, and macromolecular protein degradation during fermentation and aerobic exposure of SBM in simulated actual production. The results demonstrated that the increase in crude protein content and reduction in crude fiber content were considerably more pronounced after fermentation for 30 days (d) and subsequent aerobic exposure, compared to 3 d. It is also noteworthy that the treated group exhibited a greater degree of macromolecular protein degradation relative to the control and 30 d of fermentation relative to 3 d. Furthermore, after 30 d of fermentation, adding LAB and protease significantly inhibited the growth of undesired microbes including coliform bacteria and aerobic bacteria. In the mixed group, the microbial diversity decreased significantly, and Firmicutes replaced Cyanobacteria for bacteria in both groups' fermentation.

Comparative study of the bacterial community of organic and conventional cow's milk

Agricultural practises such as conventional and organic farming can potentially affect the microbial communities in milk. In the present study, the bacterial diversity of milk was investigated using high-throughput sequencing on ten organic and ten conventional farms in the Azores, a region where milk production is largely based on year-round grazing systems. The microbiota of milk from both production systems was dominated by Bacillota, Pseudomonadota, Actinomycetota and Bacteroidota. The organic milk showed greater heterogeneity between farms, as reflected in the dispersion of diversity indices and the large variation in the relative abundances of the dominant genera. In contrast, conventionally produced milk showed a high degree of similarity within each season. In the conventional production system, the season also had a strong influence on the bacterial community, but this effect was not observed in the organic milk. The LEfSe analysis identified the genus Iamia as significantly (p < 0.05) more abundant in organic milk, but depending on the season, several other genera were identified that distinguished organic milk from conventionally produced milk. Of these, Bacillus, Iamia and Nocardioides were associated with the soil microbiota in organic farming.

Effects of Dried Tea Residues of Different Processing Techniques on the Nutritional Parameters, Fermentation Quality, and Bacterial Structure of Silaged Alfalfa

The effects of dried tea residues on the nutritional parameters and fermentation quality, microbial community, and in vitro digestibility of alfalfa silage were investigated. In this study, dried tea residues generated from five different processing techniques (green tea, G; black tea, B; white tea, W; Pu'er raw tea, Z; Pu'er ripe tea, D) were added at two addition levels (5% and 10% fresh weight (FW)) to alfalfa and fermented for 90 days. The results showed that the tea residues increased the crude protein (CP) content (Z10: 23.85%), true protein nitrogen (TPN) content, DPPH, and ABST radical scavenging capacity, total antioxidant capacity (T-AOC), and in vitro dry matter digestibility (IVDMD) of the alfalfa silage. Moreover, the pH, ammonia-N (NH3-N) content, and acetic acid (AA) content decreased (p < 0.05). The effects of tea residues were promoted on these indicators with increasing tea residue addition. In addition, this study revealed that the influence of dried tea residues on the nutritional quality of alfalfa silage was greater than that on fermentation quality. Based on the nutrient composition, the addition of B or G to alfalfa silage can improve its silage quality, and these tea byproducts have the potential to be used as silage additives.

Synergistic effects of ferulic acid esterase-producing lactic acid bacteria, cellulase and xylanase on the fermentation characteristics, fibre and nitrogen components and microbial community structure of Broussonetia papyrifera during ensiling

BACKGROUND

The high fibre content of whole plants of Broussonetia papyrifera limits its efficient utilization. Ferulic acid esterase (FAE), in combination with xylanase, can effectively cleave the lignin-carbohydrate complex, promoting the function of cellulase. However, little is known about the impact of these additives on silage. To effectively utilize natural woody plant resources, FAE-producing Lactiplantibacillus plantarum RO395, xylanase (XY) and cellulase (CE) were used to investigate the dynamic fermentation characteristics, fibre and nitrogen components and microbial community structure during B. papyrifera ensiling.

RESULTS

Broussonetia papyrifera was either not treated (CK) or treated with FAE-producing lactic acid bacteria (LP), CE, XY, LP + CE, LP + XY or LP + CE + XY for 3, 7, 15, 30 or 60 days, respectively. In comparison with those in the CK treatment, the L. plantarum and enzyme treatments (LP + CE, LP + XY and LP + XY + CE), especially the LP + XY + CE treatment, significantly increased the lactic acid concentration and decreased the pH and the contents of acid detergent insoluble protein and NH3 -N (P < 0.05). Enzyme addition improved the degradation efficiency of lignocellulose, and a synergistic effect was observed after enzyme treatment in combination with LP; in addition, the lowest acid detergent fibre, neutral detergent fibre, hemicellulose and cellulose contents were detected after the LP + CE + XY treatment (P < 0.05). Moreover, CE, XY and LP additions significantly improved the microbial community structure, increased the relative abundance of Lactiplantibacillus and Firmicutes, and effectively inhibited undesirable bacterial (Enterobacter) growth during ensiling.

CONCLUSION

FAE-producing L. plantarum and the two tested enzymes exhibited synergistic effects on improving the quality of silage, which indicates that this combination can serve as an efficient method for improved B. papyrifera silage utilization. © 2023 Society of Chemical Industry.

Effects of inoculation and dry matter content on microbiome dynamics and metabolome profiling of sorghum silage

Sorghum forage was ensiled for 90 days at two dry matter (DM) contents (27 vs. 39%) without or with Lactiplantibacillus plantarum inoculation. On day 90 of fermentation, silages were sampled to assess the microbial community dynamics and metabolome profile. L. plantarum inoculation improved silage quality, as shown by a lower pH and greater acetic acid concentration. Loss of DM remained unaffected by L. plantarum inoculation but was greater in low- vs. high-DM sorghum silages (14.4 vs. 6.62%). The microbiome analysis revealed that Pseudomonas congelans represented the dominant species of the epiphytic microbiota in both low- and high-DM sorghum forage before ensiling. However, L. buchneri represented the dominant species at the end of ensiling. Ensiling fermentation resulted in distinct metabolic changes in silages with varying DM content. In low-DM silages, ensiling fermentation led to the accumulation of 24 metabolites and a reduction in the relative concentration of 13 metabolites. In high-DM silages, ensiling fermentation resulted in an increase in the relative concentration of 26 metabolites but a decrease in the concentration of 8 metabolites. Compared to non-inoculated silages, L. plantarum inoculation resulted in an increased concentration of 3 metabolites and a reduced concentration of 5 metabolites in low-DM silages. Similarly, in high-DM silages, there was an elevation in the relative concentration of 3 metabolites, while a decrease in 7 other metabolites. Ten metabolites with bio-functional activity were identified, including chrysoeriol, isorhamnetin, petunidin 3-glucoside, apigenin, caffeic acid, gallic acid, p-coumaric acid, trans-cinnamic acid, herniarin, and 3,4-dihydroxy-trans-cinnamate. This study presents a comprehensive analysis of microbiome and metabolome profiling of sorghum forage during ensiling as a function of DM content and L. plantarum inoculation, with a particular emphasis on identifying metabolites that may possess bio-functional properties. KEY POINTS: • DM loss was not different by L. plantarum but higher in low- vs. high-DM silage. • L. buchneri dominated ensiling, regardless of DM level. • 10 metabolites with bio-functional activity were identified.

Bacillus velezensis promotes the proliferation of lactic acid bacteria and influences the fermentation quality of whole-plant corn silage

Objective

This study aimed to investigate the promoting effect of a Bacillus velezensis (BV) strain on lactic acid bacteria (LAB) and determine its influence on the fermentation quality and aerobic stability of silage.

Methods

Flat colony counting method was used to evaluate the effect of BV on the growth of LAB. Freshly harvested whole-plant corn was inoculated separately with BV and L. plantarum (LP), along with an uninoculated control group (CK), and assessed at 1, 3, 5, 7, 15, and 30 days of ensiling.

Results

The results indicated that BV exhibited a proliferative effect on Weissella confusa, Lactobacillus plantarum L-2, and Pediococcus pentosaceus. And exhibited a more rapid pH reduction in BV-inoculated silage compared with that in CK and LP-inoculated silage during the initial stage of ensiling. Throughout ensiling, the BV and LP experimental groups showed enhanced silage fermentation quality over CK. Additionally, relative to LP-inoculated silage, BV-inoculated silage displayed reduced pH and propionic acid. BV also prolonged aerobic stability under aerobic conditions. The microbial community in BV-inoculated silage showed greater stability than that in LP-inoculated silage. Additionally, Firmicutes and Lactobacillus exhibited more rapid elevation initially in BV versus LP-inoculated silage, but reached comparable levels between the two inoculation groups in the later stage.

Conclusion

In summary, BV enhanced the efficacy and aerobic stability of whole-plant corn silage fermentation by stimulating LAB proliferation.

The influence of low-temperature resistant lactic acid bacteria on the enhancement of quality and the microbial community in winter Jerusalem Artichoke (Helianthus tuberosus L.) silage on the Qinghai-Tibet Plateau

Jerusalem Artichoke (Helianthus tuberosus L.), an emerging "food and fodder" economic crop on the Qinghai-Tibet Plateau. To tackle problems such as incomplete fermentation and nutrient loss occurring during the low-temperature ensilage of Jerusalem Artichokes in the plateau's winter, this study inoculated two strains of low-temperature resistant lactic acid bacteria, Lactobacillus plantarum (GN02) and Lactobacillus brevis (XN25), along with their mixed components, into Jerusalem Artichoke silage material. We investigated how low-temperature resistant lactic acid bacteria enhance the quality of low-temperature silage fermentation for Jerusalem Artichokes and clarify its mutual feedback effect with microorganisms. Results indicated that inoculating low-temperature resistant lactic acid bacteria significantly reduces the potential of hydrogen and water-soluble carbohydrates content of silage, while increasing lactic acid and acetic acid levels, reducing propionic acid, and preserving additional dry matter. Inoculating the L. plantarum group during fermentation lowers pH and propionic acid levels, increases lactic acid content, and maintains a dry matter content similar to the original material. Bacterial community diversity exhibited more pronounced changes than fungal diversity, with inoculation having a minor effect on fungal community diversity. Within the bacteria, Lactobacillus remains consistently abundant (>85%) in the inoculated L. plantarum group. At the fungal phylum and genus levels, no significant changes were observed following fermentation, and dominant fungal genera in all groups did not differ significantly from those in the raw material. L. plantarum exhibited a positive correlation with lactic acid and negative correlations with pH and propionic acid. In summary, the inoculation of L. plantarum GN02 facilitated the fermentation process, preserved an acidic silage environment, and ensured high fermentation quality; it is a suitable inoculant for low-temperature silage in the Qinghai-Tibet Plateau.

Influences of Growth Stage and Ensiling Time on Fermentation Characteristics, Nitrite, and Bacterial Communities during Ensiling of Alfalfa

This study examined the impacts of growth stage and ensiling duration on the fermentation characteristics, nitrite content, and bacterial communities during the ensiling of alfalfa. Harvested alfalfa was divided into two groups: vegetative growth stage (VG) and late budding stage (LB). The fresh alfalfa underwent wilting until reaching approximately 65% moisture content, followed by natural fermentation. The experiment followed a completely randomized design, with samples collected after the wilting of alfalfa raw materials (MR) and on days 1, 3, 5, 7, 15, 30, and 60 of fermentation. The growth stage significantly influenced the chemical composition of alfalfa, with crude protein content being significantly higher in the vegetative growth stage alfalfa compared to that in the late budding stage (p < 0.05). Soluble carbohydrates, neutral detergent fiber, and acid detergent fiber content were significantly lower in the vegetative growth stage compared to the late budding stage (p < 0.05). Nitrite content, nitrate content, nitrite reductase activity, and nitrate reductase activity were all significantly higher in the vegetative growth stage compared to the late budding stage (p < 0.05). In terms of fermentation parameters, silage from the late budding stage exhibited superior characteristics compared to that from the vegetative growth stage. Compared to the alfalfa silage during the vegetative growth stage, the late budding stage group exhibited a higher lactate content and lower pH level. Notably, butyric acid was only detected in the silage from the vegetative growth stage group. Throughout the ensiling process, nitrite content, nitrate levels, nitrite reductase activity, and nitrate reductase activity decreased in both treatment groups. The dominant lactic acid bacteria differed between the two groups, with Enterococcus being predominant in vegetative growth stage alfalfa silage, and Weissella being predominant in late budding stage silage, transitioning to Lactiplantibacillus in the later stages of fermentation. On the 3rd day of silage fermentation, the vegetative growth stage group exhibited the highest abundance of Enterococcus, which subsequently decreased to its lowest level on the 15th day. Correlation analysis revealed that lactic acid bacteria, including Limosilactobacillus, Levilactobacillus, Loigolactobacillus, Pediococcus, Lactiplantibacillus, and Weissella, played a key role in nitrite and nitrate degradation in alfalfa silage. The presence of nitrite may be linked to Erwinia, unclassified_o__Enterobacterales, Pantoea, Exiguobacterium, Enterobacter, and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium.

Effects of Vachellia mearnsii Tannin Extract as an Additive on Fermentation Quality, Aerobic Stability, and Microbial Modulation of Maize Silage

Maize silage is produced to alleviate the effects of forage shortages on ruminant animals, particularly during the dry season. Microorganisms play a significant role in silage fermentation and thus, to a large extent, determine the silage quality. The modulation of silage microorganisms may help to inhibit undesirable bacteria and improve the silage quality. Therefore, condensed tannin extract from Vachellia mearnsii bark was used as an additive in maize silage during ensiling. Hence, this study evaluated the effects of a tannin extract (condensed tannin) additive on the fermentative quality, aerobic stability, and bacterial composition of maize silage. A mini-silo experiment on maize with five treatments was conducted for 75 days. The silage treatments were as follows: (T1) maize forage with no inoculation (negative control); (T2) maize forage inoculated with LAB and 1% tannin extract; (T3) maize forage inoculated with LAB only (positive control); (T4) and maize forage inoculated with LAB and 2% tannin extract; (T5) maize forage inoculated with LAB and 3% tannin extract. The results showed that the additives modulated the silage microorganism composition. However, this was without affecting the silage's fermentative quality and aerobic stability. All the silages recorded a pH below 4.2, which indicated well-fermented silage. The tannin extract suppressed the growth of undesirable bacteria, such as Dysgonomonas, Gluconacetobacter and Clostridium genera, while promoting desirable bacteria, such as Lactobacillus and Weissella genera, which were attributed to the silage quality. It is thus concluded that tannins can be strategically used as silage additives to modulate the microbial composition of silage and improve the silage quality by promoting the dominance of the desirable bacteria in the silage.

Microbiomics and volatile metabolomics-based investigation of changes in quality and flavor of oat (Avena sativa L.) silage at different stages

Objective

This study aimed to analyze the fermentation quality, microbial community, and volatile metabolites of oat silage harvested at two different stages, while examining the correlation between microorganisms and volatile metabolites.

Methods

Oats were harvested at two growth stages (pre-heading [PRH] and post-heading [POH] stages), followed by 90 days of natural fermentation, with 6 replicates per treatment. Pre- and post-silage samples were randomly selected for nutrient composition, fermentation parameters, microbial population, and high-throughput sequencing analysis. Volatile metabolomics analysis was also performed on samples after 90 days of fermentation to detect differences in flavor quality after silage.

Results

The effect of growth stage on the nutrient content of oats was significant, with pre-heading oats having higher crude protein and post-heading oats having higher water soluble carbohydrates content (p < 0.05). Following a 90-day fermentation period, the pH and ammonia nitrogen/total nitrogen levels in the PRH-90 (silage from pre-heading oats after 90 days of fermentation) group demonstrated a significant decrease (p < 0.05), whereas the lactic acid content was notably higher compared to the POH-90 (silage from post-heading oats after 90 days of fermentation) group (p <0.05). Lactiplantibacillus dominated in the PRH-90 group and Enterococcus dominated in the POH-90 group, with abundances of (> 86%) and (> 87%), respectively. The differential volatile metabolites of the two treatment groups were dominated by esters and terpenoids, and the differences in flavor were mainly concentrated in sweet, green, and fruity odors. The results of Kyoto encyclopedia of genes and genomes pathway enrichment analysis demonstrated three major metabolic pathways: phenylpropanoid biosynthesis, phenylalanine metabolism, and biosynthesis of secondary metabolites. Specific microorganisms were significantly correlated with flavor indicators and flavor metabolites. Lactiplantibacillus was significantly positively correlated with flavor substances indicating sweet and fruity flavors, contributing to good flavor, while Enterococcus was significantly and positively correlated with flavor substances indicating bad flavors.

Conclusion

In summary, growth stage had significant effects on nutritional components, fermentation parameters and flavor quality of oats, with the fermentation process dominated by Lactiplantibacillus leading to good flavor, while the fermentation process dominated by Enterococcus led to the development of poor flavor.

Effects of Condensed Tannins on Bacterial and Fungal Communities during Aerobic Exposure of Sainfoin Silage

BACKGROUND

Sainfoin is a forage legume that is widely distributed around the world and is beneficial for animals owing to the characteristics of its condensed tannins (CTs), which, from certain plants, can prolong the aerobic stability of silage.

METHODS

The present study investigated whether sainfoin CTs can prolong aerobic stability by adding polyethylene glycol (PEG) to inactivate CT activity in the silage system.

RESULTS

The results showed that aerobic stability increased under the PEG treatment (p < 0.05). Ammonia nitrogen (0.71 g/kg DM vs. 0.94 g/kg DM; p < 0.05) was higher in the PEG-treated group compared with the control after 3 d of aerobic exposure. BA was detected only in the PEG-treated group upon aerobic exposure. Yeasts were more abundant in the control compared with the PEG-treated group after 7 d of aerobic exposure, after which the relative abundance of Lactobacillus was lower in the PEG-treated group (65.01% vs. 75.01% in the control; p < 0.05), while the relative abundance of Pediococcus was higher in the PEG-treated group compared with the control (10.9% vs. 4.49%, respectively; p < 0.05).The relative abundances of Apiotrichum and Aspergillus were lower in the control than in the PEG-treated group after 7 d of aerobic exposure.

CONCLUSIONS

The results suggested that sainfoin CTs decreased aerobic stability, but could inhibit certain bacteria and fungi, such as Pediococcus and Apiotrichum, and preserve the protein content during the aerobic exposure of silage.

Monitoring of an Applied Beneficial Trichoderma Strain in Root-Associated Soil of Field-Grown Maize by MALDI-TOF MS

The persistence of beneficial microorganisms in the rhizosphere or surrounding soil following their application is a prerequisite for the effective interaction with the plant or indigenous microbial communities in the respective habitats. The goal of the study was to analyze the establishment and persistence of the applied beneficial Trichoderma harzianum (OMG16) strain in the maize root-associated soil depending on agricultural practice (soil management practice, N-fertilizer intensity) in a field experiment. A rapid identification of the inoculated strain OMG16 is essential for its monitoring. We used a culture-based approach coupled to matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis for the rapid identification of the inoculated Trichoderma strain as part of the beneficial microbe consortium (BMc). We isolated 428 fungal isolates from eight treatments of the field experiment. Forty eight percent of the isolated fungi equivalent to 205 fungal isolates were identified as Trichoderma, of which 87% (=179 isolates) were obtained from the fields inoculated with BMc. Gene sequence analysis showed a high similarity of the MALDI-TOF MS-identified Trichoderma, with that of the inoculated Trichoderma harzianum OMG16 confirming the re-isolation of the added beneficial fungus. This study highlighted the use of MALDI-TOF MS analysis as a quick, cost-effective detection and efficient monitoring tool for microbial-based bioinoculants in the field.

Investigation on Fermentation Characteristics and Microbial Communities of Wheat Straw Silage with Different Proportion Artemisia argyi

Mycotoxins, secondary metabolites of fungi, are a major obstacle to the utilization of animal feed for various reasons. Wheat straw (WS) is hollow, and miscellaneous bacteria can easy attach to its surface; the secondary fermentation frequency after silage is high, and there is a risk of mycotoxin poisoning. In this study, a storage fermentation process was used to preserve and enhance fermentation quality in WS through the addition of Artemisia argyi (AA), which is an effective method to use WS resources and enhance aerobic stability. The storage fermentation of WS treated with AA had lower pH and mycotoxin (AFB1 and DON) values than the control due to rapid changes in microbial counts, especially in the 60% AA groups. Meanwhile, the addition of 60% AA improved anaerobic fermentation profiles, showing higher lactic acid contents, leading to increased efficiency of lactic acid fermentation. A background microbial dynamic study indicated that the addition of 60% AA improved the fermentation and aerobic exposure processes, decreased microbial richness, enriched Lactobacillus abundance, and reduced Enterobacter and Aspergillus abundances. In conclusion, 60% AA treatment could improve the quality by increase fermentation quality and improve the aerobic stability of WS silage by enhancing the dominance of desirable Lactobacillus, inhibiting the growth of undesirable microorganisms, especially fungi, and reducing the content of mycotoxins.

Fermentation profile, aerobic stability, and microbial community dynamics of corn straw ensiled with Lactobacillus buchneri PC-C1 and Lactobacillus plantarum PC1-1

Corn straw is suitable for preservation as silage despite being neglected due to its varying chemical composition, yield, and pathogenic influence during ensiling. This study examined the effects of beneficial organic acid-producing lactic acid bacteria (LAB), including Lactobacillus buchneri (Lb), L. plantarum (Lp), or their combination (LpLb), on fermentation profile, aerobic stability, and microbial community dynamics of corn straw harvested at late maturity stage after 7d, 14d, 30d, and 60d of ensiling. Higher levels of beneficial organic acids, LAB counts, and crude protein (CP), and lower levels of pH and ammonia nitrogen were detected in LpLb-treated silages after 60d. Lactobacillus, Candida, and Issatchenkia abundances were higher (P < 0.05) in Lb and LpLb-treated corn straw silages after 30d and 60d ensiling. Additionally, the positive correlation between Lactobacillus, Lactococcus and Pediococcus, and the negative correlation with Acinetobacter in LpLb-treated silages after 60d emphasizes a potent interaction mechanism initiated by organic acid and composite metabolite production to reduce pathogenic microorganisms' growth. Also, a significant correlation between Lb and LpLb-treated silages with CP and neutral detergent fiber after 60d further highlights the synergistic effect of incorporating L. buchneri and L. plantarum for improved nutritional components of mature silages. The combination of L. buchneri and L. plantarum improved aerobic stability, fermentation quality, and bacterial community and reduced fungal population after 60d of ensiling, which are properties of well-preserved corn straw.

Detoxifying mycotoxins and antifungal properties of two rumen-derived Enterococcus species in artificially contaminated corn silages

BACKGROUND

Mycotoxins contamination in food and feed has emerged as an issue of serious concern because they pose serious health risks to both humans and livestock. The study aimed to evaluate the effects of two rumen-derived Enterococcus spp. on fermentation and hygienic quality of artificially contaminated corn silages. The toxigenic fungal-infested (FI) and non-fungal infested (NFI) corn was harvested at 1/2 milk line stage and ensiled without additives (CON) or with Enterococcus faecalis (E) or Enterococcus faecium (M).

RESULTS

The pH of FI silages was higher than that of NFI silages, the pH in NFI-M was lower than in NFI-CON. Inoculating E. faecium markedly increased lactic acid concentration compared to CON and E silages. Both E. faecium and E. faecalis decreased the deoxynivalenol (DON) and zearalenone (ZEN) concentrations compared with the CON for FI silages, while E. faecium was more effective in eliminating aflatoxin B₁ (AFB₁ ). The FI silage had higher bacterial and fungal Shannon indexes than NFI silages. The relative abundance (RA) of Aspergillus and Fusarium marked a decline from day 5 to day 90. Inoculating E. faecium and E. faecalis reduced the RA of Penicillium compared to CON. In vitro mycotoxins removal assay indicated that E. faecium was more effective in AFB₁ detoxification while having lower detoxifying ZEN capacity than E. faecalis.

CONCLUSION

Inoculating rumen-derived Enterococcus spp. isolates alleviated the negative effects of fungal infestation on the fermentation and hygienic quality of corn silages by changing the microbial communities and detoxifying mycotoxins. © 2023 Society of Chemical Industry.

Effects of Different Types of LAB on Dynamic Fermentation Quality and Microbial Community of Native Grass Silage during Anaerobic Fermentation and Aerobic Exposure

Silage of native grasses can alleviate seasonal forage supply imbalance in pastures and provide additional sources to meet forage demand. The study aimed to investigate the effects of Lactobacillus plantarum (LP), Lactobacillus buchneri (LB), and Lactobacillus plantarum in combination with Lactobacillus buchneri (PB) on the nutritional quality, fermentation quality, and microbial community of native grass silage at 2, 7, 15, and 60 days after ensiling and at 4 and 8 days after aerobic exposure. The results showed that dry matter content, crude protein content, the number of lactic acid bacteria, and lactic acid and acetic acid content increased and pH and ammonia nitrogen content decreased after lactic acid bacteria (LAB) inoculation compared with the control group (CK). LP had the lowest pH and highest lactic acid content but did not have greater aerobic stability. LB maintained a lower pH level and acetic acid remained at a higher level after aerobic exposure; aerobic bacteria, coliform bacteria, yeast, and molds all decreased in number, which effectively improved aerobic stability. The effect of the compound addition of LAB was in between the two other treatments, having higher crude protein content, lactic acid and acetic acid content, lower pH, and ammonia nitrogen content. At the phylum level, the dominant phylum changed from Proteobacteria to Firmicutes after ensiling, and at the genus level, Lactiplantibacillus and Lentilactobacillus were the dominant genera in both LAB added groups, while Limosilactobacillus was the dominant genus in the CK treatment. In conclusion, the addition of LAB can improve native grass silage quality by changing bacterial community structure. LP is beneficial to improve the fermentation quality in the ensiling stage, LB is beneficial to inhibit silage deterioration in the aerobic exposure stage, and compound LAB addition is more beneficial to be applied in native grass silage.

Response of fermentation quality and microbial community of oat silage to homofermentative lactic acid bacteria inoculation

Oat (Avena sativa L.) is one of the important forage crops in the world. However, oat grown in Southwest China has higher moisture content and their preservation face significant challenges. In addition, existing commercial lactic acid bacteria (LAB) have poor fermentation effects in hot and humid regions. Consequently, the current study investigated the response of oat fermentation quality and microbial community to self-selected LAB inoculation. The treatments were: CK, sterilized water; LP694, Lactobacillus plantarum 694; LR753, Lactobacillus rhamnosus 753; and LPLR, LP694 combined with LR753, followed by 1, 3, 7, 14, and 60 days (d) of fermentation. The results showed that LAB inoculation significantly raised the lactic acid content, and decreased the level of pH value, acetic acid, and ammonia-N in oat silage. The LR753 group had a significantly higher (p < 0.05) lactic acid content (60.95 g kg-1 DM), and lower pH value (3.95) and ammonia-N content (10.1 g kg-1 DM) followed by the LPLR group. The LR753 showed lower NDF (54.60% DM) and ADF (39.73% DM) contents than other groups. The Lactobacillus was a prevalent genus in LAB-treated groups, and its relative abundance reached maximum in LP694 (69%) on day 3, while in the LR753 group (72%) on 60 days. The Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus fermentum became the dominant species in LAB-treated groups with fermentation time. The Lactobacillus genus was positively correlated with WSC (R = 0.6, p < 0.05), while negatively correlated with pH (R = -0.5, p < 0.05), and BA (R = -0.5, p < 0.01). Overall, the LR753 group had better fermentation quality and preservation of nutritional components providing theoretical support and guidance for future oat silage production in Southwest China.

Effect of different regions on fermentation profiles, microbial communities, and their metabolomic pathways and properties in Italian ryegrass silage

Introduction

Italian ryegrass is less studied in northern China due to high-quality forage grass has not been fully utilized. Full utilization of high-quality forage grass helps to alleviate the shortage of forage grass in winter and spring season and guarantee stable development of livestock production. Consequently, this study was aimed to evaluate the effects of different regions in northern China on the fermentative products, bacterial community compositions, and metabolic pathways and metabolites of Italian ryegrass silage.

Methods

The Italian ryegrass was harvested from three regions (Ordos-WK; Hohhot-AK; Ulanqab-SYK) and ensiled for 60 days. Single molecule real-time (SMRT) sequencing and ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) were used to analyze bacterial communities and metabolites, respectively.

Results

After 60 d of fermentation, the SYK group had the lowest pH (4.67), the highest lactic acid contents (95.02 g/kg DM) and largest lactic acid bacteria populations (6.66 log₁₀ cfu/g FM) among the treatment groups. In addition, the SYK group had the highest abundance of Lactiplantibacillus plantarum (63.98%). In SYK group, isoquinoline alkaloid biosynthesis was the significantly enriched (p < 0.05) and high-impact value (0.0225) metabolic pathway. In AK group, tryptophan metabolism the was the significantly enriched (p < 0.001) and high-impact value (0.1387) metabolic pathway. In WK group, citrate cycle (TCA cycle) was the significantly enriched (p < 0.001) and high-impact value (0.1174) metabolic pathway. Further, Lactiplantibacillus plantarum was positively correlated with cinnamic acid, tetranor 12-HETE, D-Mannitol, (2S)-2-amino-4-methylpentanoic acid L-Leucine, guanine, isoleucyl-aspartate and 3,4-Dihydroxyphenyl propanoate, but negatively correlated with isocitrate and D-mannose.

Discussion

In conclusion, this study can improve our understanding of the ensiling microbiology and metabolomics in different regions to further regulate the fermentation products and promote livestock production.

A meta-analysis to observe silage microbiome differentiated by the use of inoculant and type of raw material

Silage fermentation is naturally carried out by lactic acid bacteria (LAB) to mainly produce lactic acid (LA) and other organic acids as preservatives. Along with fermentation time, the growth of LAB will replace and suppress undesirable microorganisms. This meta-analysis study aimed to explore silage microbiome differentiated by LAB inoculants and type of raw materials. A total of 37 articles with 185 studies and 475 datasets were used for building up the meta-database. Data were subjected to the mixed model methodology. The parameters observed were silage quality and silage microbiome post-ensiling process. Results revealed that four bacterial genera along with Weissella dominated the post-ensiling process. The addition of lactic acid inoculants in the silage has increased the abundance of Lactobacillus spp. and decreased the Shannon index significantly. Moreover, the abundance of both L. plantarum and L. buchneri increased, and subsequently, Weissella, Pseudomonas, Proteobacteria, pH value, ammoniacal nitrogen (NH₃-N), coliforms, and the yeasts were decreased significantly due to the addition of LAB inoculants in silage (p < 0.05). Environmental factors such as temperature affected the existence of Pseudomonas, Exiguobacterium, and Acinetobacter. However, the dry matter, LA, acetic acid (AA), the ratio of LA to AA, and the LAB population were enhanced significantly (p < 0.05). Among the LAB types, the lowest abundance of Pseudomonas was due to the LAB group, while the lowest abundance of Weissella and Proteobacteria was due to the addition of the combined LAB group. In conclusion, the addition of LAB is effectively enhancing the silage microbiome and silage quality by altering bacterial diversity and the metabolic products of the silage materials for safe preservation.

Exploring the bacterial community succession and metabolic profiles of Lonicera japonica Thunb. residues during anaerobic fermentation

Discarding Lonicera japonica Thunb. (LJT) residues containing many active metabolites create tremendous waste. This study aimed to effectively use LJT residues by anaerobic fermentation. Fermentation significantly decreased the pH values and reduced the abundance of undesirable bacteria (potential pathogenic and biofilm-forming) while increasing Lactobacillus abundance. Compound additive use further improved fermentation quality (significantly increased the lactic acid (LA) content and decreased the pH values and ammonia nitrogen (a-N) content) and nutrient quality (significantly decreased the acid detergent fiber (ADF) content and increased the water-soluble carbohydrate (WSC) content) and optimized the microbial community (increased the Lactobacillus abundance). Fermentation also altered the flavonoids, alkaloids and phenols contents in the residues with minor effects on the functional metabolites amounts. The LJT residues metabolic profile was mainly attributed to its epiphytic bacteria, with a small contribution from the compound additive. Thus, compound additives may improve anaerobic LJT residue fermentation without functionally impairing the metabolites.

Preservation characteristics and bacterial communities of crimped ensiled barley grains modulated by moisture content and additive application

Information about the relationships between preservation characteristics and main bacterial communities of fermented feeds can guide decision making during feed preservation and silage additive development. The objective was to evaluate fermentation quality, aerobic stability, microbial quality and bacterial profile of crimped barley grains ensiled under three moisture contents (MC): 228 (low MC), 287 (medium MC) and 345 (high MC) g/kg fresh matter; and using four additive treatments: 1. Control (CONT), 2. Formic and propionic acid-based additive (FPA), 3. Inoculation with homofermentative and heterofermentative strains of lactic acid bacteria (LAB), and 4. Salt-based additive (SALT). There was a quadratic effect (p < 0.05) of incremental MC on pH where greater decline happened from low (5.81) to medium (4.83) MC than from medium to high (4.28) MC, while lactic acid concentration and aerobic stability increased in a linear manner (p < 0.05). Ammonia-N and acetic acid concentrations increased quadratically (p < 0.05) with increasing levels of MC. The effects of additives depended on MC so that improvements in preservation characteristics in response to LAB and SALT were observed at medium and high MC, while FPA was effective at all MC levels. A minor shift was observed in bacterial ecology from raw material towards low MC samples, with Erwiniaceae sp., Enterobacterales spp. and Pseudomonas dominating the fermentation. A major change occurred in medium and high MC materials, where Fructilactobacillus dominated the fermentation in CONT, FPA and SALT silages. LAB-treated silages at medium and high MC resulted in a distinguished pattern with dominance of Lentilactobacillus followed by Lactiplantibacillus. Most abundant communities in the samples, such as Fructilactobacillus, Erwiniaceae sp., Enterobacterales spp. and Pseudomonas, were correlated with several fermentation characteristics. Our results showed that crimped barley grains could be successfully ensiled under various MC and additive treatments. Low MC feeds had higher risk to be aerobically unstable while high MC resulted in more extensive fermentation, with potentially poor fermentation quality. The suitable additive depends on the raw material characteristics as LAB and SALT require relatively high MC to be effective, while FPA showed consistent improvements over all MC levels used in the current study. Awareness of the MC of grain prior to ensiling allows to identify the risks to preservation quality and provides information for choosing an effective additive.

Lactobacillus plantarum and propionic acid improve the fermentation quality of high-moisture amaranth silage by altering the microbial community composition

Objective

The objective of this study was to determine the effect of Lactobacillus plantarum (L. plantarum) and propionic acid (PA) on the microbial community and fermentation performance of high-moisture amaranth silage.

Methods

Amaranth silages were rown without addition (AhGCK) as a control and with L. plantarum JYLP-002 (AhGLP) or propionic acid (AhGPA) and then were opened after 60 days of ensiling to determine the microbial community and fermentation quality.

Results

Crude protein (CP) content, lactic acid (LA) content, and lactic acid bacteria (LAB) counts were significantly higher in AhGLP and AhGPA compared with those in AhGCK (p < 0.05). In contrast, pH, acetic acid (AA) content, and yeast and aerobic bacteria counts were significantly lower in AhGLP and AhGPA compared with those in AhGCK (p < 0.05). In addition, propionic acid (PA) levels were markedly higher in AhGPA (p < 0.05). In terms of microbial communities, the silage in the additive groups showed an increased relative abundance of Lactiplantibacillus plantarum and Lentilactobacillus buchneri and a reduced relative abundance of Enterobacter cloacae and Clostridium tyrobutyricum. The abundance of Xanthomonas oryzae was significantly increased in AhGPA, but completely inhibited in the silage supplemented with L. plantarum. Spearman's correlation analysis revealed that Lentilactobacillus buchneri and Levilactobacillus brevis were positively associated with LA and negatively associated with pH. Conversely, Clostridium tyrobutyricum and Enterobacter cloacae were negatively associated with LA, but positively associated with pH and AA content. AA content was inversely correlated with Lentilactobacillus buchneri. Functional prediction analysis showed that LAB dominated the three groups of silage and the silages containing additives had improved carbohydrate and amino acid metabolism compared with the control silage; in particular, the AhGLP group had more heterotypic fermentation processes and a richer metabolic pathway. Furthermore, the epiphytic Lactiplantibacillus plantarum and Lentilactobacillus buchneri could inhibit the reproductive activity of undesirable microorganisms to a certain extent, thus slowing the spoilage process of the silage.

Conclusion

In conclusion, L. plantarum can improve fermentation characteristics by modulating the microbial community attached to high-moisture amaranth silage and will prove useful for preserving high-moisture silage.

Fermentation quality and bacterial ecology of red clover dominated silage modulated by different management factors

Identification of bacterial communities in both the raw material and the subsequent silages provides new insights into understanding the silage fermentation process. The objective was to evaluate how different silage management factors affect silage preservation characteristics, the microbiome, and their correlations. A red clover dominated sward was used as the raw material and ensiled in pilot scale using a 3 × 4 design, with three management conditions including the level of compaction (loose and tight), and further, for the tightly compacted silages contamination with soil and faeces was conducted; and four different additive treatments with different modes of action: Control without additive (CONT), formic and propionic acid-based additive (FPA), homofermentative lactic acid bacteria inoculant (LAB) and salt-based additive (SALT). Samples of the raw material and subsequent silages were taken and routinely analysed, including DNA extraction and PCR amplification using universal primers. Tight compaction reduced slightly the extent of silage fermentation, but contamination with soil and faeces stimulated a non-desired type of fermentation with higher concentrations of ethanol, acetic acid and propionic acid and a higher pH. Use of LAB and SALT had only minimal effects on silage fermentation, but FPA clearly restricted fermentation and resulted in a better fermentation quality (lower pH, ammonia N and acetic acid concentration) of the silages compared to CONT. The FPA silages presented greater diversity of bacterial communities compared to the other silages. Proteobacteria were the most abundant in raw material, followed by Firmicutes, and major shifts happened in these communities during the silage fermentation process. Weissella was found in small amounts in the raw material but it dominated in the silages. The most abundant communities in the silages, such as Weissella, Lactobacillus and Pseudomonas, were correlated with several silage fermentation characteristics. Use of FPA improved fermentation quality of silages, but SALT and LAB differed from CONT to a smaller extent. All additives modified the bacterial profiles of grasses ensiled under different management conditions. The combination of parameters related to silage quality and bacterial communities provided a deeper understanding of the silage fermentation process and how they can be manipulated to obtain better feed quality.

Current approaches on the roles of lactic acid bacteria in crop silage

Lactic acid bacteria (LAB) play pivotal roles in the preservation and fermentation of forage crops in spontaneous or inoculated silages. Highlights of silage LAB over the past decades include the discovery of the roles of LAB in silage bacterial communities and metabolism and the exploration of functional properties. The present article reviews published literature on the effects of LAB on the succession, structure, and functions of silage microbial communities involved in fermentation. Furthermore, the utility of functional LAB in silage preparation including feruloyl esterase-producing LAB, antimicrobial LAB, lactic acid bacteria with high antioxidant potential, pesticide-degrading LAB, lactic acid bacteria producing 1,2-propanediol, and low-temperature-tolerant LAB have been described. Compared with conventional LAB, functional LAB produce different effects; specifically, they positively affect animal performance, health, and product quality, among others. In addition, the metabolic profiles of ensiled forages show that plentiful probiotic metabolites with but not limited to antimicrobial, antioxidant, aromatic, and anti-inflammatory properties are observed in silage. Collectively, the current knowledge on the roles of LAB in crop silage indicates there are great opportunities to develop silage not only as a fermented feed but also as a vehicle of delivery of probiotic substances for animal health and welfare in the future.

Effect of lactobacilli inoculation on protein and carbohydrate fractions, ensiling characteristics and bacterial community of alfalfa silage

Introduction

Alfalfa (Medicago sativa L.) silage is one of the major forages with high protein for ruminants.

Methods

The objective of this study was to investigate the effects of lactobacilli inoculants on protein and carbohydrate fractions, ensiling characteristics and bacterial community of alfalfa silage. Wilted alfalfa (35% dry matter) was inoculated without (control) or with Lactobacillus coryniformis, Lactobacillus casei, Lactobacillus plantarum, and Lactobacillus pentosus and ensiled for 7, 15, and 60 days.

Results and discussion

Silage inoculated with L. pentosus was superior to L. coryniformis, L. casei, L. plantarum in improving the fermentation quality of alfalfa silage, as indicated by the lowest ammonia nitrogen content and silage pH during ensiling. There was minor difference in water soluble carbohydrates content among all silages, but L. pentosus inoculants was more efficient at using xylose to produce lactic acid, with lower xylose content and higher lactic acid content than the other inoculants. Compared with the control, L. pentosus inoculants did not affect true protein content of silage, but increased the proportions of buffer soluble protein and acid detergent soluble protein. The L. pentosus inoculants reduced the bacterial diversity In alfalfa silage with lower Shannon, Chao1, and Ace indices, and promoted relative abundance of lactobacillus and decreased the relative abundance of Pediococcus compared with the control. As well as L. pentosus inoculants up-regulated amino acid, carbohydrate, energy, terpenoids, and polypeptides metabolism, and promoted lactic acid fermentation process. In summary, the fermentation quality and nutrient preservation of alfalfa silage were efficiently improved by inoculated with L. pentosus.

Fermentation quality, bacterial community, and predicted functional profiles in silage prepared with alfalfa, perennial ryegrass and their mixture in the karst region

There is little information regarding the dynamics of fermentation products and the bacterial community in silage prepared with alfalfa (MS), perennial ryegrass (LP), and their mixture in the karst region. In this study, we explored the effects of combining MS with LP in different ratios (100% MS, 70% MS + 30% LP, 50% MS + 50% LP, 30% MS + 70% LP and 100% LP; fresh matter basis) on silage chemical composition, fermentation quality, bacterial communities and predicted functions during the ensiling process. Each treatment was prepared in triplicate and stored at room temperature (22–25°C) for 7, 15, and 45 days. The dry matter (DM) and water-soluble carbohydrate content of the silages increased as the LP proportion in the mixed silage increased; at 45 days, the 70% MS + 30% LP, 50% MS + 50% LP and 30% MS + 70% LP silages contained higher (p &lt; 0.05) CP content than the 100% MS and 100% LP silages. The 30% MS + 70% LP and 100% LP silages exhibited lower (p &lt; 0.05) pH and higher (p &lt; 0.05) LA content than the other silages; at 45 days, none of the silages contained PA or BA. As fermentation proceeded, the abundance of harmful (Enterobacteriaceae and Sphingomonas) and beneficial (Lentilactobacillus, Lactiplantibacillus, Secundilactobacillus, and Levilactobacillus) microorganisms decreased and increased, respectively, as the LP proportion in the mixed silage increased. The predicted functional distribution of microbial communities and metabolic pathways revealed that the 30% MS + 70% LP and 100% LP silages had a stronger capacity for fermentation and a weaker capacity for nitrate reduction than the other silages. Moreover, as the fermentation proceeded, the 30% MS + 70% LP and 100% LP treatments enhanced the functions of “Metabolism,” “Genetic information processing” and “Organismal systems” at level 1, the functions of “Amino acid metabolism” and “Nucleotide metabolism” at level 2, and the functions of “Metabolic pathways,” “Biosynthesis of secondary metabolites,” “Biosynthesis of antibiotics” and “Purine metabolism” at level 3. Thus, adding LP could improve the fermentation quality of MS silage by changing the composition and metabolic function of microbes; furthermore, ensiling 30% alfalfa with 70% ryegrass can produce high-quality silage in the karst region.

Effects of Lactiplantibacillus plantarum and Lactiplantibacillus brevis on fermentation, aerobic stability, and the bacterial community of paper mulberry silage

The present study investigated the dynamic profiles of fermentation quality, aerobic stability, and the bacterial community of paper mulberry silage inoculants without (Control) or with Lactiplantibacillus plantarum (LP), Lactiplantibacillus brevis (LB), or their combination (LPLB), which was screened from naturally fermented paper mulberry. The results showed that the inoculated treatments had significantly reduced neutral detergent fiber, water-soluble carbohydrates, and ammoniacal nitrogen contents compared with the control after 60 days of ensiling (the decreased proportion of LP, LB, and LPLB treatments ranged from 7.33%-11.23%, 9.60%-21.44%, and 21.53%-29.23%, respectively, p < 0.05). The pH value of the LP and LB treatments was significantly lower than that of the control after 60 days of ensiling (4.42 and 4.56 vs. 4.71, p < 0.05). The LP treatment promoted lactic acid accumulation and LAB number compared with the control (66.59% vs. 54.12% and 8.71 log10 CFU/g vs. 8.52 log10 CFU/g, respectively, p < 0.05), and the LB and LPLB treatments inhibited the growth of yeast and mold after 14 days of fermentation. After 5 days of aerobic exposure, both the LB and LPLB treatments increased the aerobic stability time and acetic acid content (from 29 to 75 h and 16.14%-48.72%, respectively, p < 0.05), inhibited the growth of yeast and mold, and did not detect butyric acid. Additionally, the bacteria community of each treatment was dominated by Aerococcus on day 3 of ensilage (accounting for 54.36%-69.31%), while the inoculated treatments reduced the abundance of Aerococcus on day 60 (from 59.73% to 85.16%, p < 0.05), and Lactobacillus became the dominant genus (accounting for 54.57%-70.89%). Inoculation of L. plantarum effectively maintained the acidic environment at the end of the fermentation system by maintaining the abundance of Lactobacillus, maximizing the preservation of dry matter and protein, and reducing protein corruption. Inoculation of L. brevis alone or in combination with L. plantarum significantly inhibited the growth of mold and improved the aerobic stability of paper mulberry silage.

Fermentation weight loss, fermentation quality, and bacterial community of ensiling of sweet sorghum with lactic acid bacteria at different silo densities

Sweet sorghum is an important forage in arid and semi-arid climatic regions. This study aimed to reveal the fermentation weight loss (FWL), fermentation quality, and bacterial community of ensiling of sweet sorghum with lactic acid bacteria LAB; (Lactiplantibacillus plantarum and Lentilactobacillus buchneri) at different silo densities. For this study, sweet sorghum was harvested at the first spikelet of inflorescence stage and ensiled without or with LAB (CK or L) in polyethylene laboratory-scale silos (diameter, 20 cm; height, 30 cm) at densities of 650 (CK_650 and L_650), 700 (CK_700 and L_700), and 750 kg/m3 (CK_750 and L_750), respectively. The FWL, fermentation quality, microbial counts, and bacterial community of the silage were assessed after 100 days of ensiling. L_750 had a lower FWL than CK_650, _700, and _750 after 100 days of ensiling (P &lt; 0.005), and the FWL was affected by silo density and inoculating LAB (P &lt; 0.005). All silages had low pH (&lt;4.0) and ammonia nitrogen content (&lt;50 g/kg total nitrogen) and did not contain propionic and butyric acids; moreover, inoculating LAB increased lactic and acetic acids (P &lt; 0.005). Bacterial communities in inoculated and uninoculated silages were clustered together, respectively, and clearly separated from each other. The total abundance of Lactiplantibacillus and Lentilactobacillus in fresh forage was &lt;1%. Lactiplantibacillus had the highest abundance in all silages (from 71.39 to 93.27%), followed by Lentilactobacillus (from 3.59 to 27.63%). Inoculating LAB increased the abundance of Lentilactobacillus in each silo density (P &lt; 0.005) and decreased Lactiplantibacillus in the silage in densities of 700 and 750 kg/m3 (P &lt; 0.005); moreover, increasing silo density decreased Lactiplantibacillus abundance and increased Lentilactobacillus abundance in inoculated silages (P &lt; 0.005). Overall, sweet sorghum silage showed satisfactory fermentation quality, with a density of no &lt;650 kg/m3, and inoculating LAB improved fermentation quality and reduced FWL. Lactiplantibacillus and Lentilactobacillus presented as minor taxa in fresh sweet sorghum and dominated the bacterial community of all silages. Inoculating LAB was the main factor affecting the bacterial community of sweet sorghum silage. Moreover, inoculating LAB and increasing silo density can contribute to the decreasing Lactiplantibacillus abundance and increasing Lentilactobacillus abundance.

Effect of exogenous microorganisms on the fermentation quality, nitrate degradation and bacterial community of sorghum-sudangrass silage

This study aims to investigate the effects of adding Lactobacillus buchneri (LB), Lactobacillus brevis (LBR) and Bacillus subtilis (BS) on the fermentation quality, nitrate degradation and bacterial community of sorghum-sudangrass silage. The results showed that the addition of LB significantly increased the pH and acetic acid content (p < 0.05), but high-quality silage was obtained. The addition of LBR and BS improved the fermentation quality of sorghum-sudangrass silage. The use of additives reduced the nitrate content in sorghum-sudangrass silage. The LB group increased the release of N₂O at 3–7 days of ensiling (p < 0.05), and LBR and BS increased the release of N₂O at 1–40 days of ensiling (p < 0.05). On the first day of ensiling, all silages were dominated by Weisslla, over 3 days of ensiling all silages were dominated by Lactobacillus. Acinetobacter, Serratia, Aquabacterium, and unclassified_f_enterobacteriaceae showed significant negative correlations with nitrate degradation during sorghum-sudangrass ensiling (p < 0.05). The BS and LBR groups increased the metabolic abundance of denitrification, dissimilatory nitrate reduction, and assimilatory nitrate reduction (p < 0.05). Overall, the additive ensures the fermentation quality of sorghum-sudangrass silage and promotes the degradation of nitrate by altering the bacterial community.

Effects of antibacterial peptide-producing Bacillus subtilis, gallic acid, and cellulase on fermentation quality and bacterial community of whole-plant corn silage

In the current study, we assessed the effects of antibacterial peptide-producing Bacillus subtilis (BS), gallic acid (GA) and cellulase (CL) on the fermentation quality and bacterial community of various varieties of whole-plant corn silage. Three different varieties of whole-plant corn (Yuqing386, Enxiai298, and Nonghe35) were treated with 0.02% BS (fresh material basis), 0.2% GA (fresh material basis) and 0.02% CL (fresh material basis), after which 45 days of anaerobic fermentation were conducted. With the exception of its low dry matter content, the results showed that Yuqing386's crude protein, water-soluble carbohydrate, and lactic acid contents were significantly higher than those of the other two corn varieties. However, its acid detergent fiber and cellulose contents were significantly lower than those of the other two corn varieties. Among the three corn variety silages, Yuqing386 had the highest relative abundance of Lactobacillus at the genus level and the biggest relative abundance of Firmicutes at the phylum level. In addition, the three additives markedly enhanced the quantity of dry matter and crude protein as compared to the control group. The application of GA considerably decreased the level of neutral detergent fiber while significantly increasing the content of lactic acid and water-soluble carbohydrates. Even though all additives enhanced the structure of the bacterial community following silage, the GA group experienced the greatest enhancement. On a phylum and genus level, the GA group contains the highest relative abundance of Firmicutes and Lactobacillus, respectively. Overall, of the three corn varieties, Yuqing386 provides the best silage qualities. GA has the biggest impact among the additions employed in this experiment to enhance the nutritional preservation and fermentation quality of whole-plant corn silage.

Effect of cellulase and lactic acid bacteria on the fermentation quality, carbohydrate conversion, and microbial community of ensiling oat with different moisture contents

Oat (Avena sativa L.) is one of the most widely cultivated crops used as forage. The aim of this study was to evaluate the effects of cellulase and Lactobacillus plantarum interactions with different moisture contents on oat ensiling. Oats with three moisture contents were treated with nothing (C), cellulase (CE), lactic acid bacteria (LP), or CE+LP and ensiled for 30 and 60 days. Compared with the control, LP and CE treatments increased crude protein and lactic acid concentrations and reduced the pH and ammonia nitrogen/total nitrogen (NH₃-N/TN) ratios of silages. The addition of CE improved lignocellulosic degradation, compared with approximately 67% (LD) and 81% moisture content (HD) ensiling, CE (CE, CE+LP) ensiling in the approximately 75% moisture content (MD) group retained higher water-soluble carbohydrate, glucose, sucrose and fructose concents. The LP and CE inoculations significantly reduced the microbial community diversity, and lower values for the observed species, ACE, Chao1, and Shannon indices compared with CK-treated samples. Additives inhibited the growth of unfavorable bacteria (such as Clostridium) and increased the abundances of lactic acid bacteria (LAB); the maximum increases in the Lactiplantibacillus abundance were obtained in the LP- and CE+LP-treated samples, improving the microbial community structure in silage. In summary, adding LP and CE effectively improved the oat fermentation quality, and better performances in ensiling oat and lignocellulose degradation were obtained with LP and CE combinations, especially for the MD group of silages that were ensiled for 60 days. The addition of CE and LP at the appropriate moisture content might be helpful for producing high-quality oat silage, and also provide a simple and feasible method to enhance the effects of bacteria and enzymes.

Exploring the effect of wilting on fermentation profiles and microbial community structure during ensiling and air exposure of king grass silage

In order to better understand the effect of wilting treatment on silage, we study analyzed the fermentation quality of unwilted (CK) and wilted (WT) king grass silage, and the dynamic changes of microorganisms in silage and aerobic exposure. After 30 days of silage, WT silage significantly reduced the pH of the silage (p < 0.05) and increased the contents of lactic acid and acetic acid (p < 0.05), but did not reduce the content of Ammonia-N (p > 0.05). Wilting treatment increased bacterial and fungal diversity during silage but decreased fungal diversity during aerobic exposure. The relative abundance of Lactococcus and Enterococcus in wilting silage increased. In the aerobic exposure stage, the relative abundance of Klebsiella decreased, but the relative abundance of Enterobacter increased in wilting treatment silage. In addition, the relative abundance of Acinetobacter and Ignatzschineria increased after 5 days of aerobic exposure. In contrast with unwilted silage, wilting treatment silage after aerobic exposure had no Candida, but the relative abundance of Wickerhamomyces increased. The results showed that wilting treatment could raise the silage quality of king grass. However, WT silage did not inhibit the reproduction of harmful microorganisms during aerobic exposure and did not significantly improve the aerobic stability of silage.

Effects of different additives on the bacterial community and fermentation mode of whole-plant paper mulberry silage

The purpose of this study was to investigate the effects of inoculation with two lactic acid bacteria (LAB) strains (Lacticaseibacillus rhamnosus and Lentilactobacillus buchneri) and the addition of four corn flour proportions (0, 3, 6, and 9%) in different treatments, on the composition and function of the bacterial community in whole-plant paper mulberry silage. The different treatments promoted Lactiplantibacillus, Lentilactobacillus, and Lacticaseibacillus growth, but the microbial species responsible for fermentation differed among the treatments. High species diversity and various Gram-negative bacteria, such as Flavitalea sp., Pantoea agglomerans, Acinetobacter pittii, Turicibacter sanguinis, and Ralstonia pickettii, were found in the uninoculated LAB treatments. A beneficial bacterium, Lactobacillus johnsonii, was discovered for the first time in whole-plant paper mulberry silage. LAB inoculation simplifies the microbial community structure, and beneficial Lactobacillus as a key species aggregates in the inoculated treatment group. However, L. rhamnosus inoculation alone may have limited bacteriostatic activity against in whole-plant paper mulberry silage. Compared with silage lacking corn flour, amino sugar and nucleotide sugar metabolism, galactose metabolism, the phosphotransferase system and the pentose phosphate pathway metabolic activity were increased in corn flour-containing silage. Whole-plant paper mulberry can be used as a high-quality silage to provide high-quality feed resources for sustainable ruminant livestock production. Moreover, additive use is necessary for preparing paper mulberry silage.

Effects of Lactic Acid Bacteria Additives on the Quality, Volatile Chemicals and Microbial Community of Leymus chinensis Silage During Aerobic Exposure

Silage exposed to air is prone to deterioration and production of unpleasant volatile chemicals that can seriously affect livestock intake and health. The aim of this study was to investigate the effects of Lactobacillus plantarum (LP), Lactobacillus buchneri (LB), and a combination of LP and LB (PB) on the quality, microbial community and volatile chemicals of Leymus chinensis silage at 0, 4, and 8 days after aerobic exposure. During aerobic exposure, LP had higher WSC and LA contents but had the least aerobic stability, with more harmful microorganisms such as Penicillium and Monascus and produced more volatile chemicals such as Isospathulenol and 2-Furancarbinol. LB slowed down the rise in pH, produced more acetic acid and effectively improved aerobic stability, while the effect of these two additives combined was intermediate between that of each additive alone. Correlation analysis showed that Actinomyces, Sphingomonas, Penicillium, and Monascus were associated with aerobic deterioration, and Weissella, Pediococcus, Botryosphaeria, and Monascus were associated with volatile chemicals. In conclusion, LB preserved the quality of L. chinensis silage during aerobic exposure, while LP accelerated aerobic deterioration.

Exploring the Epiphytic Microbial Community Structure of Forage Crops: Their Adaptation and Contribution to the Fermentation Quality of Forage Sorghum during Ensiling

In this study, the effects of epiphytic microbiota from different forages on the fermentation characteristics and microbial community structure of forage sorghum silage were investigated. The gamma irradiated sterilized forage sorghum was treated through sterile water, epiphytic microbiota of forage sorghum (FSm), Sudan grass (SDm), Napier grass (NPm), and maize (MZm). NPm and SDm inoculated silages showed similar pH value and lactic acid (LA) and acetic acid (AA) contents at day 3 and 60 of ensiling. The final silage of FSm and MZm showed lower (p < 0.05) pH and AA content and a higher LA content compared to the NPm and SDm silages. Bacterial species from the Weisella genus were predominantly present in FSm, NPm, and SDm, while Lactococcus dominated the MZm silage during early ensiling. Lactobacillus was predominant in all inoculated terminal silages. Overall, the four inoculated microbiota decreased the pH value of silage and were dominated by lactic acid bacteria (LAB); however, the NPm and SDm treatments resulted in comparatively higher AA contents which could have an inhibitory effect on the secondary fermentation developed by the yeast and enhanced the aerobic stability of forage sorghum silage.

Effects of different harvest frequencies on microbial community and metabolomic properties of annual ryegrass silage

In this study, we analyzed the fermentation quality, microbial community, and metabolome characteristics of ryegrass silage from different harvests (first harvest-AK, second harvest-BK, and third harvest-CK) and analyzed the correlation between fermentative bacteria and metabolites. The bacterial community and metabolomic characteristics were analyzed by single-molecule real-time (SMRT) sequencing and ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS), respectively. After 60 days of ensiling, the pH of BK was significantly lower than those of AK and CK, and its lactic acid content was significantly higher than those of AK and CK. Lactiplantibacillus and Enterococcus genera dominate the microbiota of silage obtained from ryegrass harvested at three different harvests. In addition, the BK group had the highest abundance of Lactiplantibacillus plantarum (58.66%), and the CK group had the highest abundance of Enterococcus faecalis (42.88%). The most annotated metabolites among the differential metabolites of different harvests were peptides, and eight amino acids were dominant in the composition of the identified peptides. In the ryegrass silage, arginine, alanine, aspartate, and glutamate biosynthesis had the highest enrichment ratio in the metabolic pathway of KEGG pathway enrichment analysis. Valyl-isoleucine and glutamylvaline were positively correlated with Lactiplantibacillus plantarum. D-Pipecolic acid and L-glutamic acid were positively correlated with Levilactobacillus brevis. L-phenylalanyl-L-proline, 3,4,5-trihydroxy-6-(2-methoxybenzoyloxy) oxane-2-carboxylic acid, and shikimic acid were negatively correlated with Levilactobacillus brevis. In conclusion, this study explains the effects of different harvest frequencies on the fermentation quality, microbial community, and metabolites of ryegrass, and improves our understanding of the ensiling mechanisms associated with different ryegrass harvesting frequencies.

Effects of epiphytic and exogenous lactic acid bacteria on fermentation quality and microbial community compositions of paper mulberry silage

This study aimed to isolate, characterize, and identify lactic acid bacteria (LAB) strains from various sources and evaluate their effects on the nutritional quality, fermentation characteristics, and microbial compositions of paper mulberry (PM) after 60 days of ensiling. Forty-nine LAB strains were isolated from Phalaris arundinacea silage, pickle, and fresh PM leaves; three of these strains (Lactiplantibacillus plantarum, YC1; Levilactobacillus brevis, PC3; and Lactiplantibacillus plantarum, BP17) and one commercial inoculant Gaofuji (GFJ) were subsequently used. Compared with other treatments, PC3 and BP17 increased (P < 0.05) the LAB count and crude protein content and decreased (P < 0.05) the molds and coliform bacteria counts, pH, and ammonia-N content of PM silages. BP17 and PC3 increased the relative Lactiplantibacillus abundance and decreased that of Lelliottia and Cladosporium, improving PM silage quality. Therefore, PC3 and BP17 can improve the fermentation quality of PM silage and could be used as silage starter cultures.

Gamma-ray irradiation and microbiota transplantation to separate the effects of chemical and microbial diurnal variations on the fermentation characteristics and bacterial community of Napier grass silage

BACKGROUND

To investigate the contributions of chemical and microbial diurnal variations in fermentation characteristics and bacterial community of Napier grass silage, gamma-ray irradiated Napier grass harvested at 07.00 h (AM), 12.00 h (M) and 17.00 h (PM) was inoculated with the microbiota derived from Napier grass harvested at AM, M and PM in a 3 (irradiated forage: AM_G , M_G and PM_G ) × 3 (microbiota: AM_M , M_M and PM_M ) design and then ensiled for 14 and 60 days.

RESULTS

Napier grass harvested at various times had different chemical compositions and epiphytic microbiota prior to ensiling. For silages inoculated with the same microbiota, the pH values, residual water soluble carbohydrates and dry matter contents increased, and lactic acid, acetic acid, propionic acid, butyric acid, ethanol and volatile fatty acids contents decreased in PM_G and M_G silages compared to AM_G silages. M_M and PM_M inoculum promoted lactic acid fermentation as indicated by higher lactic acid contents and lactic/acetic acid ratios in M_M and PM_M -inculated silages compared to those in AM_M -inoculated silages after 60 days of ensiling. During ensiling, epiphytic microbiota affected the Chao1 index, operational taxonomic units (OTUs) number and Shannon index, as well as the abundances, of more than half of the top 10 abundant genera, whereas chemical composition did not affect any of the bacterial diversity and richness indices and only showed significant impacts on the abundances of two genera.

CONCLUSION

The results indicated that chemical diurnal variation exerted an influence mainly on the extent of fermentation, whereas microbial diurnal variation affected more the bacterial community and fermentation types during Napier grass ensiling. © 2022 Society of Chemical Industry.

Freeze–thaw condition limits the fermentation process and accelerates the aerobic deterioration of oat (Avena sativa) silage in the Qinghai-Tibet Plateau

The objective of this study is to determine the effect of freeze–thaw condition on the fermentation characteristics, microbial community, and aerobic stability of oat (Avena sativa) silage in the Qinghai-Tibet Plateau. Oat forage was harvested at milk ripening stage, ensiled in vacuum-sealed bags, and then stored at (1) a constant temperature of 20°C, as a control (20 group) or (2) subjected to freeze–thaw condition (alternating 20 and −5°C every 12 h; S group). The quality and microbial community in the silage were measured after 1, 3, 7, 14, and 60 days of ensiling, and the aerobic stability was measured after 60 days of ensiling at room temperature or at the two treatment temperatures. The results showed that the higher the pH, the lower the concentration of lactic acid and the ratio of lactic acid/acetic acid of the samples under freeze–thaw condition, as compared to those stored at 20°C. The dry matter content of 20 groups was significantly higher than S group (p &lt; 0.05). While ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), and water-soluble carbohydrates (WSC) had no significant difference between two groups. Lactobacillus spp., Leuconostoc spp., and Weissella spp. were the most prevalent bacterial genera in all groups. The abundance of Lactobacillus spp. in the 20 group was the highest on day 3 of ensiling (p &lt; 0.05), and it reached the peak on day 14 in the S group, but the abundance in the S group did not exceed 50% during whole fermentation process. The abundance of Enterobacterales and the count of Escherichia coli in the S group was significantly higher than 20 group (p &lt; 0.05). Interestingly, the lactic acid concentration was significant correlated with Lactobacillus spp. in 20 group, while correlated with Leuconostoc spp. in S group. The aerobic stability of the S group was lower than that of the 20 group (p &lt; 0.05). The present study indicates that the freeze–thaw condition led to insufficient fermentation degree of silage by limiting the fermentation of Lactobacillus spp. and severely reduced the aerobic stability of oat silage.

An innovative strategy to enhance the ensiling quality and methane production of excessively wilted wheat straw: Using acetic acid or hetero-fermentative lactic acid bacterial community as additives

Ensiling is an effective storage strategy for agricultural biomass, especially for energy crops (mainly energy grasses and maize). However, the ensiling of excessively wilted crop straw is limited due to material characteristics, such as a high lignocellulosic content and low water-soluble carbohydrate and moisture contents. In this study, acetic acid or hetero-fermentative lactic acid bacterial community (hetero-fermentative LAB) were employed as silage additives to improve the ensiling process of excessively wilted wheat straw (EWS). The results showed that the additives inhibited the growth of Enterobacteriaceae and Clostridium_sensu_stricto_12, whose abundances decreased from 55.8% to 0.03-0.2%, respectively. The growth of Lactobacillus was accelerated, and the abundances increased from 1.3% to 80.1-98.4% during the ensiling process. Lactic acid fermentation was the dominant metabolic pathway in the no additive treatment. The additives increased acetic acid fermentation and preserved the hemicellulose and cellulose contents, increasing the methane yield by 17.7-23.9%. This study shows that ensiling with acetic acid or hetero-fermentative LAB is an effective preservation and storage strategy for efficient methane production from EWS.

Effects of hexanoic acid on microbial communities, fermentation, and hygienic quality of corn silages infested with toxigenic fungi

BACKGROUND

This study aims to reveal the effects of hexanoic acid on the microbial communities, fermentation, and the hygienic quality of corn silages with or without fungal infection. Fungal-infested (FI) and non-infested (NFI) whole-crop corn samples were separately ensiled without (control, CON) or with hexanoic acid (Hex, 90% purity) at 0.2 g·kg^-1 fresh weight (FW).

RESULT

The addition of Hex accelerated the pH decline during the first 5 days of ensiling regardless of fungal infestation. The lactic acid (LA) concentration in Hex silages was lower than that in CON during 45 days of ensiling; however the FI-Hex silage had the highest LA concentration among treatments on day 90. The Hex silage showed lower aflatoxin B₁ (AFB₁ ), zearalenone (ZEA), and deoxynivalenol (DON) concentrations than CON for FI silages. On day 5, the addition of Hex decreased the relative abundance of Klebsiella, Pantoea, and Enterobacter compared with CON, regardless of fungal infestation. This inhibitory effect lasted until day 90 for NFI silages but disappeared for FI silages on day 90. The fungal infestation resulted in the accumulation of Candida (34.05%) and Wickerhamomyces (19.46%). Hex decreased the relative abundance of Asperigillus, Issatchenkia, and Penicillium for NFI silages on day 5; however, its inhibitory effects were not observed in FI silages on day 5.

CONCLUSION

Fungal infestation was associated with poor fermentation and hygienic quality of corn silage. Adding Hex accelerated the pH decline and maintained the antifungal activity until 90 days of ensiling, attenuating adverse effects of fungal infestation on the fermentation and preventing the accumulation of mycotoxins in corn silages. © 2021 Society of Chemical Industry.