Cenchrus fungigraminus (Juncao) is a high-yielding, fast-growing forage crop with considerable potential for livestock feed; however, optimizing its processing is essential for cost reduction and quality enhancement. This study comprised three components: (1) a comprehensive analysis of 25 on-farm silage samples from five locations in Southwest China using Grey Relational Analysis (GRA); (2) an assessment of the effects of three cutting heights (low: 100–150 cm; mid: 150–200 cm; high: 200–250 cm) on silage quality; and (3) a comparison of silage quality between natural fermentation and microbial inoculant treatments using mature Juncao (250–300 cm). The results showed that: (1) in the on-farm silage samples, carbon supplementation was significantly positively correlated with total digestible nutrients (TDN), relative feed value (RFV), ether extract (EE), and sensory evaluation (p < 0.05), and the GRA identified the top-ranked treatments, including J2, J3, J6, X6, and J5; (2) in the cutting height trials, fiber content increased significantly with cutting height (p < 0.05), while crude protein (CP) and TDN decreased significantly (p < 0.05). The 200–250 cm group exhibited optimal fermentation quality, characterized by the highest total volatile fatty acids (total VFA) and lactic acid concentrations, alongside the lowest pH and ammonia nitrogen/total nitrogen ratios (NH₃-N/TN); (3) in the inoculant comparison, the natural fermentation group demonstrated significantly higher degradation rates of acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL) compared to the microbial inoculant group, while also maintaining a lower pH, higher total VFA and lactic acid. Consequently, for on-farm production, carbon supplementation is recommended to improve silage quality. Although cutting Juncao below 200 cm provides higher nutritional value, a height of 200–250 cm is advised to ensure optimal fermentation characteristics. Furthermore, natural fermentation proves superior to microbial inoculant treatment for mature Juncao. Together, these measures offer an effective strategy for producing high-quality Juncao silage.

As a high-yield and fast-growing novel forage, Juncao (Cenchrus fungigraminus) holds significant potential for feed applications. Appropriate processing methods can effectively enhance the feeding efficacy of Juncao silage and reduce feed costs for farmers and herdsmen. In this study, Juncao at three different heights (1.0–1.5 m, 1.5–2.0 m, and 2.0–2.5 m) was selected for silage fermentation to determine the optimal harvesting height. Additionally, Juncao at a height of 2.5–3.0 m, which possesses the highest cellulose content, was selected for cellulose degradation analysis to evaluate the degradation efficiency of conventional silage additives on fiber content.The results indicated that the fiber content of Juncao silage was significantly positively correlated with growth height, whereas crude protein and crude fat contents showed a significant negative correlation. Furthermore, the total volatile fatty acid (TVFA) and lactic acid contents reached their peak in the 2.0–2.5 m (High) group. Cellulose degradation analysis revealed that the degradation rates of various cellulose components were higher under natural fermentation conditions compared to treatments with silage additives. However, further research is required to explore whether specific additives tailored for Juncao silage exist. Based on this experimental analysis, it can be concluded that utilizing 2.0–2.5 m Juncao for natural fermentation during the ensiling process can effectively improve nutritional composition and fermentation quality while achieving a higher cellulose degradation rate. Nonetheless, subsequent studies are necessary to refine and establish a complete and scientific methodology for Juncao silage production.