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In this study, the possibility of green tea waste (GTW) as a new ingredient of byproducts-mixed silage was investigated. Characteristics of GTW were low in dry matter (DM) content (20%), and high in crude protein (30 to 36%) and tannins (8.5%). The GTW was added to mixed silages composed of tofu cake, rice straw and rice bran that are locally available in Japan. In experiment 1, the effect of GTW addition to silage made from various patterns of byproducts mixture based on tofu cake was studied. In experiment 2, the effect of GTW addition and storage temperature on fermentation characteristics, nutrient contents and in vitro ruminal gas production of byproducts-mixed silages were examined. In experiment 1, GTW addition on tofu cake accelerated acetic, propionic and butyric acid accumulation in the silage. When rice straw was mixed with tofu cake, DM content was increased from 47 to 56%, lactic acid was the main acid and the pH was decreased below 4.2. In this case, GTW addition to those mixtures did not affect acid concentrations of the silage. In experiment 2, GTW addition to the byproducts mixture increased lactic acid concentration, decreased the pH and DM loss of the silages. In GTW treatments, tannin concentration was lower in the silage stored at 30째C than 15째C. Addition of GTW into the silage also increased in vitro ruminal gas production. It was concluded that addition of GTW into byproducts-mixed silage enhanced lactic acid fermentation when there were insufficient materials for lactic acid production. Utilization of GTW as an ingredient in mixed silages would be effective in enhancing fermentation characteristics, lowering tannin content and in vitro ruminal gas production.