In order to evaluate the effect of different levels of Biosaf probiotic(yeast based) in supplemental diet containing medium concentrate (65%) on growth performance and blood factors of zandi lambs, 27 male weaned lambs(29.9 ± 0.28 kg, 90 ± 5 days) were allocated to one of three treatment diets in a completely randomized design, including: 1-basal diet without probiotics (Control, C) 2-basal diet supplemented with 3 g probiotic per lamb (Low Probiotic, LP) 3-basal diet supplemented with 4.5 g probiotic per lamb (High Probiotic, HP). Basal diet was containing 2.59 MCal/ Kg ME and 15.5% crude protein.

Lambs live weight was measured at the beginning of the experiment and every two weeks interval. Dry matter intake (DMI) was measured daily. Water consumption offered ad lib. Blood sample were collected at the beginning of the trial, 42 and 84 days and analyzed for total protein, globulin, albumin, BUN, white blood cells and heterophil: lymphocyte ratio according to standard methods. Result shows DMI was unaffected by treatments (P>0.05). ADG was greater in HP group at first 4 weeks but total ADG was unaffected among treatment. Blood parameters were not significantly different among treatments (P>0.05) except BUN and total protein on 84 day. BUN and total protein were significantly higher in control group (P<0.05). It is concluded that addition of probiotic at the dose of 4.5 gr/lamb is superior to enhanced growth performance and immune response of Zandi lambs.