effect of zinc on humoral and cell-mediated immunity of broilers vaccinated against coccidiosis.

background: the aim of the present study was the comparison of humoral and cell-mediated immunity in broilers fed with different levels of zinc during a coccidiosis challenge. methods: one hundred and forty- four one-day-old broiler chicks were used with three dietary zinc (40, 120 and 200 mg/kg). at 14 d of age, all birds were inoculated orally with 5×10 3 sporulated oocysts of e. tenella . at 2, 22, 32, 42 days of age, the blood serums were tested for antibody titer against new-castle disease vaccine, using the standard hi test. on day 42 the sum of ni-trite and nitrate based on the reduction of nitrate to nitrite by cadmium and white blood cell count (wbc) using a hemocytometer were measured. results: at 42 d, levels of 120 and 200 mg significantly ( p < 0.05) increased the antibody titer in compare with the control. the peak response of cbh was observed at the level of 200 mg zn/kg diet. also both level of 120 and 200 mg zn/kg diet increased wbc count and sum of nitrite and nitrate in serum compared with the control. conclusion: the levels of 120 and 200 mg zn/kg diet could be considered as a non-pharmacologic booster of immunity in broilers chicks infected with e. tenella .