The effect of ammoniation treatment on the animal performance of rice straw was studied. The stacked rice straw was covered with polyethylene film and injected with 3% anhydrous ammonia (DM base of rice straw) and kept for eight weeks at the outdoor. The Korean Native Steers, average body weight of 285㎏, were fed all samely 1.5% concentrate of their body weight and each five of them were fed with untreated rice straw (U-RS) and NH₃ treated rice straw (NH3-RS), respectively. Average daily weight gain of steers fed NH₃-RS was significantly higher than that of steers fed U-RS (p$lt;0.05) and DMI ㎏/day and DMI g/W^(0.75) of steers fed NH₃-RS was significantly greater than that of steers fed U-RS. But feed ㎏/gain was not so significantly affected by NH₃ treatment, however the trends was apparently decreased.