A study was conducted to determine the effect of probiotic on the performance and serum parameters of broilers chickens. In completely randomized design with 4 treatments ( 0 , 0.5, 1, and 1.5 dose of probiotic levels )1 and 5 replicates of 12 birds each 240 day-old mail Hubbard Classic broiler chickens with the average weight of 42±2 gram, chickens were placed in 1 × 1.2 m pens for 42 days. Feed and body weight gain recorded weekly. 4 cc of blood samples was collected from slaughtered birds of 21 and 42 days of age, and transferred to vials for some serum parameter determination .Feed intake and serum Triglycerides were not affected by treatment at 42 days of age. Body weight and feed to gain ration at 0-21 days of age were significantly (p<0.05) improved by treatments. Serum cholesterol and HDL at 42 days of age were affected by treatments (p<0.05). Under the condition of this experiment probiotic levels added to the drinking water improves body weight and feed efficiency at 21 days of age , decreases serum cholesterol and increases serum HDL at 42 days of age.

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