| 384 one-day old AA broilers were randomly grouped into 8 (4 male and 4 female groups), each with 4 repeats, and each repeat has 12 broilers. The 4 groups of male/female were Fed with diet supplemented with Zn at 40, 80, 120 and 160mg/kg respectively. The purpose of the research is to evaluate the effects of Zinc at different levels on the broiler's immunologic potency, growth performance, and serum biochemical indices.The results showed that:1. Of the immunologic potency, thymus, bursa and spleen index showed no significant difference among every treatments (P>0.05). However, supplementation of Zinc at 40mg/kg showed higher titers of serum antibody level against Newcastle disease than 160 mg/kg (P<0.05) although no significant difference (P>0.05) was found at day21, 28 and 42. And the morphological observation of tissue slices revealed that lymphocytes in the thymus, bursa and spleen increased when Zinc was supplemented at 80mg/kg.2. Of the growth performance, no significant difference was found among all the treatments in different weeks (P>0.05) based on body weight, everyday gain of body weight and day feed consumption altogether. In early growth, 120 mg/kg of Zinc showed the best results, and in the late, 80 mg/kg best.3. Of serum biochemical indices, no differences were found base on the content of total protein and the activity of AMS serum (P>0.05), but the GOT and GPT activity were highest when supplemented with 160 mg/kg Zinc (P>0.05) and, the ALB content, uric acid and AKP activity were highest from 40 to 120mg/kg. LDH activity varied with day age and sexes, but the males showed higher than female.4. Of the slaughter indexes, based on the eviscerated weight dressing percentage, percentage of eviscerated with giblet and percentage of eviscerated yield, there showed no obvious differences among all the treatments(P>0.05).Based on above results, supplementation of Zinc at 80～120 mg/kg to diet was best.
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