In order to enhance the feeding value of rice-straw, rice straw with different formular of concentrate, rape or formic acid as an additive was ensilaged into and evaluated by laboratory method, and by a feeding trial with finishing Korean native cattle. For the evaluation of the silage quality. rice straw and rape were cut into about 3cm and concentrate levels were adjusted to 20, 30, and 40 percent and kept in a plastic silo of 200㎏ capacity. Rumen solution was taken from sheep by fistulation and used for digestibility and organic acid analysis. For feeding trial, for 90 days, silages with different formula was kept in trench silo and fed to 12 Korean native finishing cattle weighing 256㎏. The results are summarized as follows: 1. Lactic acid fermentation was improved by adding higher proportion of concentrate. 2. Digestible crude protein content was increased in the silages with 0.5 % formic acid or in the silages with higher proportion of concentrates(p$lt;0.05). 3. The pH of rumen solution was decreased in the silage with high proportion of concentrate, while lactic acid content was increased at the same condition(p$lt;0.01). 4. LWG was significantly increased to 0.9 ㎏/day in silage-fed cattle. 5. Total DM intake was significantly increased in cattle on ordinary rice straw and concentrate, however, feed efficiency(feed consumption over live weight gain) were poor(7.46 vs. 6.13). 6. Requirements of DCP and TDN in traditional fed cattle were 0.65 and 4.41 ㎏/LWG㎏ and those in silage fed cattle were 0.50 and 3.71㎏/LWG ㎏, respectively.