The microbial community of rain-soaked Sudan grass silage

Sudan grass, known for its high yield and adaptability, is widely used as forage. However, the grass in Southwest China is prone to rainfall exposure during the harvest period, leading to increased susceptibility to nutrient loss and spoilage during ensiling. This study aimed to evaluate the effects of ferulic acid esterase (FAE)-producing Lactiplantibacillus plantarum (LP), either alone or combined with cellulase and xylanase (CX) or cellulase and laccase (CL), on the fermentation quality, aerobic stability, nutrient preservation, and microbial community of rain-affected Sudan grass silage.The Sudan grass wilted to approximately 75% moisture, and treated as follows: control (CK), LP, LCX, and LCL, then stored for 60 days followed by a 7-day aerobic exposure period. Results showed that the LCX treatment significantly improved silage quality, with lowest pH, higher lactic acid (LA) and water-soluble carbohydrate contents, enhanced degradation of cellulose and hemicellulose, and increased abundance of Lactiplantibacillus (P < 0.05). However, it exhibited the poorest aerobic stability. In contrast, the LCL treatment reduced lignin content, butyric acid (BA), and fungal diversity, while increasing acetic acid, crude protein, and the relative abundance of Lentilactobacillus (P < 0.05), leading to the best aerobic stability (>168 h). After 7 days of aerobic exposure, the LCL silage maintained stable nutritional and fermentation characteristics. Rainfall exposure led to the poorest fermentation quality in the control and FAE-producing L. plantarum-only treatments, characterized by higher pH (>5.16), high BA content, significant nutrient loss, and substantial proliferation of undesirable bacteria including Enterobacter, Pantoea, and Clostridium sensu stricto_12. While, previous studies on non-rain-affected Sudan grass achieved good results using the L. plantarum addtive alone. Consequently, ensiling rain-soaked Sudan grass without additives or with only the LP is ineffective, the combination of FAE-producing LP with cellulase and xylanase (LCX) treatment could efficiently improve silage quality, but was prone to spoilage after aerobic exposure. Whereas adding LP, cellulase and laccase (LCL) effectively enhanced both fermentation quality and aerobic stability of rain-affected Sudan grass silage by optimizing the microbial community and metabolic profile.