Forty growing Barki lambs of (3:4) months age and 34.97 kg average body weight were divided randomly into four equal groups (10 animals each): Animals of T1 (control) were fed on a basal diet according to the farm feeding system regime while T2, T3, and T4 (treated) were fed as T1 plus (for T2) 1 gm of powder (prebiotics) for every 1 kg of concentrate feed given to this group, for T3 0.5 g of powder (probiotics) per 1 kg of concentrate feed and T4 were received 1 g per 1 kg of concentrate feed. The aims of the experiment were to study the effects of some feed additives, especially prebiotics, probiotics, and synbiotics, as synthetic sources, on the productive performance and feed efficiency of growing Barki lambs length of the experiment period. The results showed that the highest significant value (P≤0.05) of DMI was recorded for T4, followed by T3, T2, and then T1, and a higher non-significant value of dry matter conversion (P≥0.05) was recorded for T4. The highest significant values of (DM, OM, CP, and NFE) were recorded for T4, followed by T3, T2, and then T1 and the highest non-significant values of CF and EE were noticed for T4. There were significant (P≤0.05) differences in Blood plasma total protein, albumin, globulin, urea, creatinine, and GPT, and insignificant (P≥0.05) differences in Blood plasma cholesterol, and triglycerides. Regarding growth performance and feed efficiency, the group that received synbiotic treatment T4 showed the highest values of daily gain (P≤0.05) and DM conversion followed by Prebiotic, Preobiotic, and then the control. These results indicate that the use of synbiotics or prebiotic or probiotic as an additives to conventional or industrial feed leads to an increase in growth performance and feed conversion efficiency, increasing the the blood plasma total protein and reducing the levels of urea, creatinine, cholesterol, triglyceride, and liver enzymes which affects the economic return of raising lambs