Modulation of the microbial community and the fermentation characteristics of wrapped natural grass silage inoculated with composite bacteria

This study evaluated the effects of composite bacterial inoculants on the fermentation quality, microbial community composition, and nutrient preservation of natural grass silage produced in Hulunbuir, Inner Mongolia. Four treatment groups were set, each using distinct combinations of lactic acid bacteria: a control group (C) with no inoculant and three inoculated groups (Group B: Lentilactobacillus buchneri and Pediococcus pentosaceus; Group P: Lactiplantibacillus plantarum A1 and Lactiplantibacillus plantarum LP-21; and Group M: Lactiplantibacillus plantarum, Enterococcus faecium, and Pediococcus pentosaceus). After 240 days of ensiling, the inoculated groups exhibited significantly higher contents of crude protein and dry matter (DM) and lower ammonia nitrogen, neutral detergent fiber, and acid detergent fiber levels than the control group. The M group demonstrated superior fermentation performance, exhibiting the lowest pH (C 5.15; B 4.77; P 4.64; and M 4.57), the highest lactic acid concentration (C 3.40% DM; B 6.80% DM; P 7.73% DM; and M 8.00% DM), and an optimal microbial composition dominated by Lactiplantibacillus and Lentilactobacillus. These improvements were attributed to Lactiplantibacillus plantarum, a bacterium that can produce a substantial amount of lactic acid through homofermentation, thereby lowering the pH, inhibiting the activity of undesirable microorganisms, and enhancing nutrient preservation. High-throughput sequencing revealed shifts in the dominant bacterial phyla from Proteobacteria in raw grass to Firmicutes in silage, with inoculants significantly influencing microbial diversity and functional profiles. Functional prediction indicated enhanced carbohydrate metabolism and nutrient preservation in the inoculated groups. These findings underscore the potential of tailored bacterial inoculants and advanced wrapping technology to improve the quality of silage and thus support sustainable livestock production.