Microbial ecological mechanism of Blumea balsamifera residue promoting fermentation quality and improving feed value of Pennisetum silage

Pennisetum is the most widely used forage in tropical regions around the world but its silage preservation is often challenged by high temperature, humidity, and the proliferation of undesirable bacteria. Blumea balsamifera (L.) DC., a native medicinal plant and industrial crop, produces residues with notable antibacterial and antioxidant properties, suggesting potential as a silage additive. However, its effects and underlying mechanisms on silage fermentation and feeding value are unclear. In this study, we evaluated the impact of B. balsamifera residue on the fermentation quality, chemical composition, digestibility, antioxidant activity, microbial community succession, assembly processes, and ecological network characteristics of Pennisetum silage. Our findings demonstrate that adding 10% residue significantly ( P < 0.05) improved fermentation quality, antioxidant capacity, nutritional composition, and in vitro dry matter digestibility. Specifically, the powder treatment increased lactic acid content (KG10P vs. CK, P < 0.05), while the fresh material showed similar improvements (KG10 vs. CK, P < 0.05). Moreover, microbial diversity and community composition were markedly altered: Lactobacillus became dominant (> 90%), while undesirable bacteria such as Aeriscardovia , Clostridium sensu stricto , and Pseudomonas were suppressed (< 1%). Further, the addition of B. balsamifera modified microbial succession patterns, increased the abundance of lactic acid bacteria, and reduced undesirable taxa. Co-occurrence network analysis revealed predominantly cooperative microbial interactions, with B. balsamifera enhancing network stability by reducing tightness, complexity, and natural connectivity. Community assembly processes also shifted: untreated silage was governed by deterministic processes, while residue addition introduced varying contributions of stochastic processes, with powder treatments largely stochastic and fresh treatments shaped by both deterministic and stochastic processes in a ratio-dependent manner. Overall, moderate addition of B. balsamifera residue improved Pennisetum silage fermentation and feeding value by optimizing microbial communities and their interaction networks.