Isolation, Identification and Spoilage Capability of Specific Spoilage Organisms on Silage During Aerobic Deterioration

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.