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 Newcastle disease vaccine, using the standard HI test. On day 42 the sum of nitrite 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.