Abstract: As the dominant rice cultivar in Tianjin, Xiaozhan rice is characterized by its robust stems and high yield. However, its high silica and low sugar content, combined with Tianjin's humid climate, often result in elevated mycotoxin contamination and inadequate fermentation during conventional micro-silage processes. This study investigated the effects of a combined lactic acid bacteria and cornmeal micro-silage treatment on fermentation quality and dairy cattle feeding performance. The results demonstrated that the treatment combining 1% cornmeal with compound lactic acid bacteria（LAC group）significantly improved（P<0.05）the fermentation quality compared to the control（CON group）with lactic acid bacteria alone, as evidenced by increased crude protein content, starch content, and 30-hour NDF digestibility（NDFD30）. Notably, while aflatoxin B1 and deoxynivalenol（DON）levels were significantly reduced（P<0.05）, zearalenone（ZEN）content showed a significant increase（P<0.05）, suggesting a differential impact on mycotoxin profiles during the micro–silage process. Feeding trials with lactating cows revealed that replacing oat hay with micro-silage-treated Xiaozhan rice straw had no significant impact（P>0.05）on milk yield or milk composition. In conclusion, compared to traditional micro-silage methods, the combined use of lactic acid bacteria and cornmeal significantly enhanced the fermentation quality of Xiaozhan rice straw. This approach can effectively replace partial oat hay in dairy rations, maintaining production performance while reducing feed costs, thereby offering a practical solution for agricultural waste valorization and cost-effective dairy farming in Tianjin.

Key words: Xiaozhan rice straw, micro-silage fermentation, fermentation quality, dairy cow performance