A feeding trial with twenty-seven male weaned Zandi lambs (initial body weight 27.1±0.38 kg) was conducted to evaluate the effect of different levels of Saccharomyces cerevisiae SC47 in diet containing high concentrate (85%) on the growth performance, blood parameters and immune system status. Lambs were allocated to one of three treatment diets in a completely randomized design with 3 replicates and 3 observations per replicate including: 1) basal diet without yeast, control diet; (CD) 2) basal diet with 3 g yeast per lambper day, low yeast; (LY) and 3) basal diet supplemented with 4.5 g yeast per lambper day, high yeast; (HY). Regarding dry matter intake (DMI), there was no significant difference among treatments (P>0.05). Average daily gain (ADG) was greater in HY group, but differences among treatments were not significant (P>0.05). Feed conversion ratio (FCR) was not significantly affected by dietary treatments (P>0.05). Differences between concentrations of total protein, globulin and albumin/globulin ratio (A/G) were significant (P<0.05). The highest amount of total protein and globulin was observed in LY group (P>0.05). Lambs in CD group had the highest amount of A/G ratio. No significant differences were found for the hematology results (P>0.05). No significant differences were detected in differential white blood cells, except neutrophil band that was greater in HY group at the twelfth week (P<0.05).It is concluded that the use of dietary live yeast in high concentration can improve performance (P>0.05), plasma biochemical metabolites(P<0.05) and hematological parameters (P>0.05) in Zandi lambs. Manuscript profile