Abstract: To investigate the influence of different ratios of rice straw on the fermentation quality of alfalfa and wheat bran mixed silage, this study conducted a series of experiments in which different ratios of rice straw (0, 5%, 10%, 15% and 20%) were added to the mixed silage and its fermentation quality, nutritional quality, and aerobic stability were analyzed after 30 days. It was found that: 1) There were significant differences in pH, water soluble carbohydrates (WSC), acid detergent fiber (ADF) and NH₃-N/TN between the control group (0) and the other groups (P<0.05). When the ratio of rice straw is increased, the pH, ADF, neutral detergent fiber (NDF) and aerobic stability of the mixed silage tended to increase while the values for crude protein (CP), WSC, relative feed value (RFV) and V-Score decreased. 2) As determined from the V-Score, silage quality for the 0 and 5% treatments was superior, quality of the 10% and 15% treatments was fairish and quality of the 20% treatment was considered to be inferior. 3) After 64 and 72 h aerobic exposure, the 0 and 5% treatments were 2 ℃ above ambient temperature, while the aerobic stability times for the 10%, 15% and 20% treatments were all above 168 h. Furthermore, after 4 days of aerobic exposure, the 0, 5%, 10% and 20% treatments exhibited a rapid change of pH, but for the 15% treatment the pH did not change much. In conclusion, the recommended mixing ratio for incorporation of rice straw into mixed alfalfa-wheat bran silage, is not more than 5% rice straw.

Key words: mixed silage, rice straw, fermentation quality, nutritional quality, aerobic stability