Exploring the ensiling characteristics and bacterial community of red clover inoculated with the epiphytic bacteria from temperate gramineous grasses

Responses of microbial community dynamics, co-occurrences, functional shifts, and natural fermentation profiles of Elymus nutans silage to altitudinal gradients

IMPORTANCE

On the Qinghai-Tibet Plateau (QTP), feed shortages are common due to cold environmental conditions and the short growing season of crops. Therefore, effective preservation, such as the ensiling of local forage, is becoming increasingly important to balance the seasonal imbalance between the forage supply and the nutritional needs of domestic animals in this area. However, the structure of the microbial community of the forage, which is influenced by climatic conditions such as altitude differences, has a major impact on the fermentation quality and microbial succession of the ensiled forage. Therefore, we investigated microbial community dynamics, co-occurrence, functional shifts, and natural fermentation profiles of Elymus nutans silage as a function of altitudinal gradients. Results show that silage from Chenduo at higher elevations has better fermentation quality and higher abundance of Lacticaseibacillus and Levilactobacillus than ensiled forage from other regions. This work may contribute to guiding for silage production in QTP.

Effect of sodium diacetate on fermentation, aerobic stability, and microbial diversity of alfalfa silage

Alfalfa (Medicago sativa L.) is a vital source of forage protein for ruminants, yet its ensiling poses challenges due to high buffering capacity and low water-soluble carbohydrates (WSC). This study investigated the impact of sodium diacetate (SDA) on alfalfa silage quality and aerobic stability. SDA was applied at four different rates to wilted alfalfa on a fresh basis: 0 g/kg, 3 g/kg, 5 g/kg, and 7 g/kg, and silages were ensiled in laboratory-scale silos for 45 days, followed by 7 days of aerobic exposure. A 16S rRNA gene sequencing assay using GenomeLab™ GeXP was performed to determine the relationship between dominant isolated lactic acid bacteria species and fermentation characteristics and aerobic stability on silage. The results showed that Lentilolactobacillus brevis, Pediococcus pentosaceus and Enterococcus faecium were the most prevalent bacteria when silos were opened, whereas Weissella paramesenteroides, Bacillus cereus, B. megaterium and Bacillus spp. were most prevalent bacteria after 7 days of aerobic exposure. Dry matter, pH, and WSC content were not affected by SDA, but doses above 5 g/kg induced a homofermentative process, which increased lactic acid concentration and lactic acid to acetic acid ratio, decreased yeast count during aerobic exposure, and improved aerobic stability. These findings offer useful information for optimizing SDA usage in silage, assuring improved quality and longer storage, and thereby improving animal husbandry and sustainable feed practices.

Epiphytic microbiota in Swedish grass-clover herbage and the effect of silage additives on fermentation profiles and bacterial community compositions of the resulting silages

AIMS

To investigate the epiphytic microbiota in grass-clover herbage harvested at different sites and occasions and to explore the effect of different silage additives on the resulting silage microbiota.

METHODS AND RESULTS

Herbage was harvested from grass-clover leys at geographically distributed sites in a long-term field experiment in Sweden, in early and late season of two consecutive years. Different silages were made from the herbage using: (1) no additive, (2) acid-treatment, and (3) inoculation by starter culture. Herbages were analysed for botanical and chemical composition, and the resulting silages for products of fermentation. Bacterial DNA was extracted from herbage and silage samples, followed by sequencing using Illumina 16S rRNA amplicon sequencing. Herbage microbiota showed no clear correlation to site or harvesting time. Silage additives had a major effect on the ensiling process; inoculation resulted in well fermented silages comprising a homogenous microbiota dominated by the genera Lactobacillus and Pediococcus. A minor effect of harvest time was also observed, with generally a more diverse microbiota in second-harvest silages. Untreated silages showed a higher relative abundance (RA) from non-lactic acid bacteria compared to acid-treated silages. In most silages, only a few bacterial amplicon sequence variants contributed to most of the RA.

CONCLUSIONS

The epiphytic microbiota in grass-clover herbage were found to be random and not dependent on site. From a microbial point of view, the most predictable and preferable silage outcome was obtained by inoculation with a starter culture. Acid-treatment with formic- and propionic acid surprisingly resulted in a less preferable silage. Silage making without additives cannot be recommended based on our results.

Dry matter content and inoculant alter the metabolome and bacterial community of alfalfa ensiled at high temperature

Alfalfa silage fermentation quality, metabolome, bacterial interactions, and successions as well as their predicted metabolic pathways were explored under different dry matter contents (DM) and lactic acid bacteria (LAB) inoculations. Silages were prepared from alfalfa with DM contents of 304 (LDM) and 433 (HDM) g/kg fresh weight and inoculated with Lactiplantibacillus plantarum (L. plantarum, LP), Pediococcus pentosaceus (P. pentosaceus, PP), or sterile water (control). The silages were stored at a simulated hot climate condition (35°C) and sampled at 0, 7, 14, 30, and 60 days of fermentation. The results revealed that HDM significantly improved the alfalfa silage quality and altered microbial community composition. The GC-TOF-MS analysis discovered 200 metabolites in both LDM and HDM alfalfa silage, mainly consisting of amino acids, carbohydrates, fatty acids, and alcohols. Compared with LP and control, PP-inoculated silages had increased concentrations of lactic acid (P < 0.05) and essential amino acids (threonine and tryptophan) as well as decreased pH, putrescine content, and amino acid metabolism. However, alfalfa silage inoculated with LP had higher proteolytic activities than control and PP-inoculated silage, as revealed by a higher concentration of ammonia nitrogen (NH₃-N), and also upregulated amino acid and energy metabolism. HDM content and P. pentosaceus inoculation significantly altered the composition of alfalfa silage microbiota from 7 to 60 days of ensiling. Conclusively, these results indicated that inoculation with PP exhibited great potential in enhancing the fermentation of silage with LDM and HDM via altering the microbiome and metabolome of the ensiled alfalfa, which could help in understanding and improving the ensiling practices under hot climate conditions. KEY POINTS: • HDM improved fermentation quality and declined putrescine content of alfalfa silage • P. pentosaceus inoculation enhanced the fermentation quality of alfalfa silage • P. pentosaceus is an ideal inoculant for alfalfa silage under high temperature.

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.

Fermentation Profiles, Bacterial Community Compositions, and Their Predicted Functional Characteristics of Grass Silage in Response to Epiphytic Microbiota on Legume Forages

This study aimed to investigate the effect of epiphytic microbiota from alfalfa and red clover on the fermentative products, bacterial community compositions, and their predicted functional characteristics in Italian ryegrass silage. By microbiota transplantation and γ-ray irradiation sterilization, the irradiated Italian ryegrass was treated as follows: (1) sterile distilled water (STIR); (2) epiphytic microbiota on Italian ryegrass (IRIR); (3) epiphytic microbiota on alfalfa (IRAL); and (4) epiphytic microbiota on red clover (IRRC). The irradiated Italian ryegrass was ensiled for 1, 3, 7, 15, 30, and 60 days. STIR had similar chemical components with fresh Italian ryegrass. IRAL had higher lactic acid concentrations [64.0 g/kg dry matter (DM)] than IRIR (22.3 g/kg DM) and IRRC (49.4 g/kg DM) on day 3. IRRC had the lowest lactic acid concentrations (59.7 g/kg DM) and the highest pH (4.64), acetic acid (60.4 g/kg DM), ethanol (20.4 g/kg DM), and ammonia nitrogen (82.6 g/kg DM) concentrations and Enterobacteriaceae [9.51 log10 cfu/g fresh weight (FW)] populations among treatments on day 60. On days 3 and 60, Lactobacillus was dominant in both IRIR (42.2%; 72.7%) and IRAL (29.7%; 91.6%), while Hafnia-Obesumbacterium was predominant in IRRC (85.2%; 48.9%). IRIR and IRAL had lower abundances of "Membrane transport" than IRRC on day 3. IRIR and IRAL had lower abundances of phosphotransacetylase and putative ATP-binding cassette transporter and higher abundances of arginine deiminase on day 3. IRAL had the highest abundance of fructokinase on day 3. Overall, inoculating epiphytic microbiota from different legume forages changed the fermentative products, bacterial community compositions, and their predicted functional characteristics in Italian ryegrass silage. The microbial factors that result in the differences in fermentative profiles between legume forage and grass were revealed. Knowledge regarding the effect of epiphytic microbiota could provide more insights into the improvement of silage quality.