Effect of Cordyceps militaris Residue and Lactiplantibacillus plantarum on Fermentation Quality and Bacterial Community of Alfalfa Silage

In order to reduce the environmental burden associated with <i>Cordyceps militaris</i> residue, we conducted a study to explore the feasibility of <i>Cordyceps militaris</i> residue as a silage additive. The experimental treatments included distilled sterile water control (CK), <i>Lactiplantibacillus plantarum</i> (LP, 1 × 10⁵ cfu/g), <i>Cordyceps militaris</i> residue (CM, 4% of fresh matter), and their combination (LP + CM). A total of 48 samples (4 treatments × 4 storage periods × 3 replicates) were prepared for the analysis of fermentation quality, chemical composition, microbial population, and bacterial community composition at days 2, 7, 28, and 45 of ensiling. Results showed that compared with the control, the CM and LP + CM treatments increased the lactic acid bacteria number and lactic acid content (<i>p</i> < 0.05), and a decrease in pH value and NH₃-N content was observed (<i>p</i> < 0.05). The bacterial diversity in the CM group was higher and lower than that in the CK group in the early and late stages of fermentation, respectively, and maintained a higher relative abundance of <i>Lactococcus</i> on day 7. <i>Lactobacillus</i> remained the predominant bacterial community at the end of fermentation. Random forest analysis indicated that <i>Lactobacillus</i> was a key determinant of the pH, lactic acid, and acetic acid levels. Consequently, the addition of <i>Cordyceps militaris</i> residue alone, or combined with <i>Lactiplantibacillus plantarum</i>, improved the quality of alfalfa silage by increasing lactic acid and lowering NH₃-N, providing a new approach for its development and utilization.