The increasing demand for high-quality forage alternatives necessitates the exploration of novel feed resources such as giant juncao (GJ). This study evaluated the feasibility of giant juncao (GJ) as silage by analyzing its fermentation products, bacterial community, and metabolic profiles during ensiling. After the natural fermentation of giant juncao (NGJ) for 1, 3, 7, 15, 30, and 60 days, a random sampling of NGJ was conducted to analyze its chemical composition, fermentation parameters, and microbial number. Fresh, 3-day, and 60-day ensiled GJ were further analyzed via high-throughput sequencing and KEGG functional prediction. Following 60 days of ensiling, NGJ displayed acetate-type fermentation with high acetic acid and ammonia nitrogen concentrations, and low lactic acid concentration and the ratio of lactic-to-acetic acid. A microbial community analysis indicated Weissella as the predominant genus during the initial fermentation phase (3-day NGJ), whereas Lactobacillus emerged as the dominant taxonomic group in the late-stage fermentation (60-day NGJ). A comparative functional analysis revealed statistically significant divergences (p < 0.05) in KEGG pathway distributions between fresh and ensiled GJ. The ensiling process notably inhibited pathways associated with lipid synthesis, cofactor and vitamin metabolism, energy production, and amino acid utilization while concurrently enhancing carbohydrate and nucleotide metabolic activities. A nutritional evaluation confirmed GJ’s suitability as a sustainable silage maize alternative, with favorable water-soluble carbohydrate (8.57% DM) and crude protein (14.6% DM) levels. To ensure optimal preservation efficacy, the experimental findings emphasize the necessity of a minimum 30-day fermentation period for stabilizing GJ silage quality. These findings offer valuable insight into the microbial and metabolic mechanisms of high-moisture silage fermentation.

Silage is a core roughage resource for ruminant production, but aerobic deterioration caused by microorganisms severely reduces its nutritional value and increases microbial risk. This study aimed to isolate and identify specific spoilage organisms (SSOs) from Napier grass silages during aerobic deterioration and evaluate their spoilage capability. Based on morphological observation, physiological and biochemical tests, and ITS rDNA sequence analysis, four SSOs were obtained as Trichosporon asahii (TA32), Nakaseomyces glabratus (NG38), Candida tropicalis (CT39), and Pichia kudriavzevii (PK41) with high lactate-assimilating and spoilage capacity. All four strains were facultative anaerobic yeast and exhibited robust growth within the range of 25–40 °C and pH 3.5–6.5. To verify their spoilage capability, these purified strains were inoculated into Napier grass silage and exposed to air. Fermentation and chemical parameters were monitored at 0, 2, 5, and 9 days. Results showed that silages inoculated with PK41 or TA32 exhibited the lowest aerobic stability with most rapid increase in pH (p < 0.05), while the control (CON) remained the highest aerobic stability (p < 0.05). These results provide a theoretical basis for developing targeted preservation technologies to extend the shelf-life of silage.