Air dry rice straw was treated with 3% anhydrous ammonia and aqueous ammonia (ammonia weight basis) in a stack during winter from October to January and feeding trials were conducted with 18 growing Holstein bulls weighing average of 231 Kg for 90 days. Treatment expenses per Kg rice straw with 3% anhydrous ammonia and 3% aqueous ammonia were 18.45 won and 28.28 won, respectively including ammonia cost, vinyl cost and labor expenses, thus, rice straw cost per Kg were 67 won for untreated straw and 85.45 and 95.28 won for anhydrous and aqueous ammonia treatment. Crude protein content of untreated rice straw was 4.2% and increased 2.2-2.4 times, and NDF & ADF content were decreased 6.5% & 5.6%, respectively sifter ammonia treatment. Rice straw intake by growing Holstein bulls, was increased 28.4% in anhydrous ammonia treated group and 43.3% in aqueous ammonia treated group and daily gains were increased 20.8% and 29.9%, respectively over untreated rice straw group. Feed conversions were 7.68 Kg/Kg gain in untreated rice straw groups and 6.95 and 6.89 Kg in anhydrous and aqueous ammonia treated groups, which ware improved 9.5% and 10.3%, respectively. Feed cost per Kg gain was 1267.91 won in untreated rice straw groups and 1,177.63 won and 1,151.57 won in anhydrous and aqueous ammonia treated rice straw groups, and feed cost reduction per Kg gain were 7.1% and 9.2% in anhydrous and aqueous ammonia treated rice straw groups, respectively.