## 4 Discussion
### The Effects of Different Additives on the Microbial Community of Corn Straw Silage  
Silage fermentation is a process in which lactic acid bacteria, naturally present on plant materials, ferment the substrate to produce lactic acid, thereby lowering the pH. During this process, lactic acid bacteria rapidly proliferate by utilizing the nutrients in the raw material, becoming the dominant microbial group, while suppressing the growth of harmful microorganisms such as clostridia and molds. Therefore, studying the microbial diversity and community structure in silage is crucial for understanding and improving the fermentation quality of silage feed. [PERSON] et al. [35] found that adding cellulase to a mixture of corn straw and soybean residue silage resulted in an increase in both the Shannon and Simpson indices in the silage samples. The results of this study indicate that after 60 days of silage, the Ace, Chao1, and Shannon indices of the additive-treated corn straw silage were significantly lower than those of the fresh material (FM) group. These findings align with those of [PERSON]. This may be because the additives provide substrates that promote lactic acid bacteria fermentation, which in turn enhances lactic acid production, lowering the pH of the silage. As a result, the complex microbial community in the silage is gradually suppressed by the dominance of lactic acid bacteria fermentation.  
Additionally, the application of xylanase during silage fermentation leads to the production of xylooligosaccharides (XOSs). XOSs act as a prebiotic, having a positive impact on the growth of beneficial microorganisms such as lactic acid bacteria. This can further promote the fermentation process and improve the overall fermentation quality of the silage. XOSs not only directly stimulate beneficial microbial growth but also indirectly enhance silage quality by maintaining a favorable microbial environment, contributing to more efficient fermentation and better preservation of nutrients [46].  
The fermentation quality of silage feed is closely linked to the microbial community composition within the silage. In this study, after 30 days of silage fermentation, the microbial community in corn straw silage was primarily composed of Firmicutes and Proteobacteria. After 60 days of fermentation, Proteobacteria were gradually replaced by Firmicutes in the microbial community. This shift is likely due to the anaerobic and acidic environment, which favors the dominance of _Lactobacillus_ (a genus within Firmicutes) during fermentation, inhibiting the growth of Proteobacteria [47]. At the genus level, unclassified_f_Alcaligenaceae_ was found in all treatment groups. This may be attributed to the addition of cellulase and xylanase, which break down cellulose and lignin, providing soluble sugars as fermentation substrates for microbial communities attached to the surface of corn straw. Consequently, unclassified_f_Alcaligenaceae_ exhibited a higher relative abundance after silage fermentation. Relevant studies suggest that unclassified_f_Alcaligenaceae_ can degrade lignin-derived compounds in the anaerobic fermentation system of silage. This capability may contribute to the breakdown of lignin during the silage process, thereby promoting overall fermentation and improving the quality of the silage feed [48].