Dynamic Changes in Microbial Diversity and Fermentation Quality of Elephant Grass and Ramie Mixed Silage During Semi-Commercial Silo Bag Production

Elephant grass–ramie mixed silage represents a promising strategy to valorize tropical forage resources for ruminant production, yet the dynamic changes in microbial community and fermentation quality during semi-commercial silo bag ensiling remain poorly understood. Elephant grass and ramie were co-ensiled at a 70:30 (w/w) ratio and stored at room temperature for 15, 30, and 45 days. Fermentation quality was evaluated by pH, lactic acid, acetic acid, and ammonia nitrogen, while bacterial and fungal communities were analyzed via 16S and ITS rRNA high-throughput sequencing in triplicate. The results revealed limited fermentation efficiency across all periods, characterized by relatively high pH (≥5.1), restricted lactic acid accumulation, and substantial butyric acid concentrations. Vertically, silage at day 30 exhibited a transient, relatively better acidification profile (lowest pH and highest lactic acid) compared to days 15 and 45, though still sub-optimal overall. Bacterial diversity increased significantly by day 45, concurrent with a marked reduction in the relative abundance of Firmicutes, whereas fungal diversity declined progressively throughout the ensiling period. Enterococcus was identified as the core functional bacterium closely correlated with key fermentation parameters, while most fungal taxa exerted negative effects on silage quality. These findings demonstrate that while a 30-day ensiling duration offers a relatively stable window under restricted acidification, the high fibrous nature and baseline composition of the mixed material present challenges for preservation. This study provides a transparent theoretical basis and underscores the critical need for technical interventions in semi-commercial elephant grass–ramie ensiling.