Abstract: [Objective] To explore the effects of cutting length on the silage quality of rice straw from different varieties. [Methods] Fresh straw from five rice varieties （Xinxiang S/R8029 Xiang, Xinxiang S/8X001, Xinxiang S/7W1446, Xinxiang S/9WH401 and Xinxiang S/R382） was used as materials, and cut into three lengths of 1-2 cm, 2-3 cm and 3-4 cm, respectively. After 60 days of sealed fermentation in vacuum bags, the microbial populations, nutritional components and fermentation characteristics were determined. Membership function analysis was used to comprehensively evaluate nutritional components and silage fermentation indexes. [Results] In terms of microbial content, different varieties, cutting length, and their interaction had significant effects on the number of lactic acid bacteria and aerobic bacteria （P<0.05）. No mold and yeast was detected in all treatments. In the 1-2 cm treatments of Xinxiang S/9WH401 and Xinxiang S/R382, the number of lactic acid bacteria was significantly lower than that in the 3-4 cm treatments （P<0.05）. In the 1-2 cm treatments of all varieties, the number of aerobic bacteria was significantly lower than that in other treatments （P<0.05）. In terms of nutritional components, under the same cutting length, there was no significant difference in crude protein content between Xinxiang S/R382 and Xinxiang S/8X001 （P>0.05）, but both were higher than those of other varieties; there was no significant difference in soluble carbohydrate content of Xinxiang S/R382 among three cutting lengths （P>0.05）, and the soluble carbohydrate contents of 1-2 cm and 2-3 cm were higher than those of other varieties. In terms of silage fermentation quality, the pH values of all varieties under the 1-2 cm treatment were significantly lower than those under the 3-4 cm treatment （P<0.05）, and the pH value slightly increased with increasing cutting length. Except for Xinxiang S/9WH401, there were no significant differences （P>0.05） in propionic acid content among treatments for the other varieties. Butyric acid was detected only in Xinxiang S/9WH401, and its content significantly increased with increasing cutting length （P<0.05）. The V-score values of Xinxiang S/R8029 Xiang, Xinxiang S/R382, Xinxiang S/8X001, and Xinxiang S/7W1446 under different cutting lengths were all above 90, with Xinxiang S/R382 showing the highest average ranking under different cutting lengths. [Conclusion] Xinxiang S/R382 is an ideal material for silage production, and the cutting length of 1-2 cm can effectively improve the silage quality of rice straw.

Key words: rice straw, cutting length, silage quality, fermentation characteristics