This work aims to analyze Optigen's effect on growing Buffalo calves as a partial replacement for soybean meal. Eighteen Buffaloes calves live body weight 303 with 14 months aged were divided into three groups based on body weight and age. All calves fed rations consisting of 2% of their LBW concentrate feed mixtures and 1% of LBW roughage to meet their recommended requirements NRC for 107 days. Animals in the control group were fed CFM1 + roughage (without Optigen) R). The tested concentrate mixture, 15 and 30% of soybean meal were replaced by Optigen CFM2 and CFM3, Rations 2 and 3 were composed of either CFM2 or CFM 3 plus roughage. No significant differences (p>.05) between all groups for the feed intake. Also, no substantial CP, CF, and EE digestibility disparities between all experimental rations. Animals fed R2 had the highest digestibility coefficients for OM and NFE, followed by animals fed R3 but, the values were lowest in the control group. The animal fed R2 recorded the highest significantly (P<0.05) TDN value. No considerable vatiations (p>0.05) for pH values between the experimental groups. Animal fed R3 recorded the highest rumenal NH3-N,concentration. The concentration of total volatile fatty acids in rumen liquor of animals fed R2 was significantly greater (p<0.05) associated with other groups. Calves fed R2 had highest daily gain value and superior feed conversion value among the other groups. It can be recommended that the addition of Optigen at a level of 0.6% under this study was more effective.