The aim of this study  was  to determine the in-vitro dry matter disappearance  (IN-VDMD %) of wheat straw (WS),  rice straw  (RS) and soy bean straw  (SBS)  before  and after treatment with urea (U), molasses (M), yeast(Y) and  combinations  of  these  ingredients. Five treatments nominated as T1 (Control), T2 (T1+U), T3 (T1+U+M), T4 (T1+U+ Y) and T5 (T1+U+M+Y) were conducted on each straw type. The IN-VDMD% was significantly (P<0.01) higher for SBS than other roughage sources in all treatments. Treatment T5 showed significantly (P<0.01) higher IN-VDMD% value than other treatments. The values being 47.49, 46.60 and 49.97% for WS, RS and SBS treated with U+M+Y respectively. As the IN-VDMD % of SBS had the highest values, it was used in in–vivo digestibility experiment on Ossimi rams.  Results of the SBS  digestibility cleared that  treatment  with urea (U), molasses (M), yeast (Y) and supplemented with fat (F) were significantly higher (P<0.01) than other  treatments  in digestibility coefficients  and feeding value  (              TDN). The TDN values were 37.96, 42.67, 43.84 and 49.92% for SBS untreated, treated with U and M, treated with U, M , Y and treated with U, M ,Y and supplemented with  fat respectively. The figures were significantly different (P<0.01). In conclusion, each treatment tested increased the IN-VDMD % of all roughages used. Treatment of  WS , RS and SBS with U, M and Y was the most  effective  treatment. Digestibility coefficients and TDN of SBS treated with U, M, Y and supplemented with fat were Promising for future application.