The study conducted to evaluate the possibility of partially or completely replacement of clover hay (CH) with Panicum maximum (Pm) on digestibility, nitrogen balance, rumen fermentation, gas production and its effect on calves performance. The digestibility trial was conducted using three males Barki sheep fed one of the four experimental rations as follow: ration (1) was concentrate fed mixture (CFM) + 100% CH (control) ; second one (T2) was fed CFM + 75% CH + 25% Pm; third one (T3) was fed CFM 50% CH + 50% Pm and fourth one (T4) fed CFM + 100% Pm. Growth trial was carried out for 90 days using 20 calves ( 5 one each group) .Rumen fermentation and gas production  trials were evaluated by 3 rams with rumen fistula .The results were showed more (P> 0.05) improvement in nutrients digestibility with T2 compared to the control and the other experimental groups . Less improvement was obtained for T4, while T3 was close to the control group. These were reflected on TDN, DCP and N balance as it was high for T2, while T4 was recorded the lowest (P> 0.05) one. No significant differences were noticed for pH values among experimental rations. T1 had the (P> 0.05) highest NH₃ concentration, but it had the lowest VFA^,s value as it was higher for T2 .Insignificant differences was found among experimental groups for microbial protein (MP) synthesis  among the ration contained Pm . While, T1 was recorded (P> 0.05) less MP, but it had the highest gas production and short chain fatty acids (SCFA) was followed by T2, meantime T4 showed less gas production and SCFA. T2 was showed the highest DWG and the best FCR; the less one was T4, while values of T1 and T3 were close together. Also, T2 had better economic efficiency followed by T3 and T1 and the lowest one was T4.