Four common Egyptian Agricultural by products used for ruminant feeding were treated with different concentrations of Probiotic (ZAD) to study the effect of treatment on chemical composition of roughages. Roughages used were rice straw (RS), wheat straw (WS), corn stover (CS) and sugar cane bagasse (SCB). Concentrations of ZAD tested in this study were 0.05, 1.0, 1.5 and 2 ml/Kg of roughage. Roughages were mixed with ZAD solution and incubated anaerobically for 4 weeks. Results indicated that treatments decreased crude fiber (CF) contents of all roughages by 17 % in CS to 30% in SCB and increased EE by multiplication of 1.45 times in WS to 4.9 times in SCB. Statistical analysis showed no significant interaction between roughage source and ZAD concentration on chemical composition of roughages except for crude protein where interaction was significant (P<.05). Results also indicated that ZAD concentration over 0 ml/kg affected CF & CP contents, it was also noticed that CP of RS showed the highest response for treatment followed by SCB and CS, respectively. Crude protein of WS was not affected by different ZAD concentration. It was concluded that ZAD concentration of 1 ml/ 1 Kg of roughage is recommended for treatment to improve roughage chemical analysis.