The current study examined the effects of probiotics (Pronifer and More-yeast) supplementation to growing lambs. 25 crossbred (Osimi×Rahmani) growing lambs of about 6–8 months age and an average initial live body weight of 25 kg were used. Lambs divided into five groups (5 lambs for each group) and the experimental period lasted for 169 days. The control group T<sub>1</sub> received concentrate feed mixture (CFM), group T<sub>2</sub> and T<sub>3</sub> received 1.5 and 3 kg Pronifer/Mg (megagram) CFM and group T<sub>4</sub> and T<sub>5</sub> received 2.5 and 5 kg More-yeast/ Mg CFM, respectively. Rumen liquor and blood samples were taken and digestibility trial was conducted at the end of the experiment. Results showed higher digestibility values for crude protein (<i>P</i><0.05) in T<sub>3</sub> and T<sub>4</sub> when compared to control. Nutritive ratio was lower (<i>P</i><0.05) in groups T<sub>3</sub> and T<sub>4</sub> than in group T<sub>2</sub>. More-yeast supplementation improved dry matter intake (<i>P</i><0.001), while a reverse trend was observed with Pronifer supplementation. All treatments had little effect on ruminal liquor except ruminal ammonia concentration in T<sub>5</sub> was lower (<i>P</i><0.05) than other treatments. The differences in most blood plasma parameters due to treatment effect were not significant, except plasma urea and globulin concentrations increased (<i>P</i><0.05) with T<sub>5</sub> treatment. The obtained results appear to indicate that Moreyeast supplementation improved lambs performance and digestibility, whereas, Pronifer supplementation enhanced digestibility.