This study was carried out to determine the effect of different levels of clove essential oil, as a natural growth promoter and probiotic on blood components, immune response and lymphoid organs in broiler chickens. A total of 240 straight run one day old commercial broiler chicks (Cobb 500) were distributed randomly into five groups. Each group was subdivided into four replicates with 12 chicks each. The control diet, diet with probiotic protexin® and diets supplemented with 150, 300 and 450 ppm clove essential oil were fed to the chickens. The results showed that different levels of clove essential oils and probiotic had no significant effect on aspartate aminotransferase, alanine aminotransferase, glucose, and albumin at 21 and 42 days of age, but at 42 days of age uric acid was significantly decreased (P<0.05) in group treated with probiotic. Administration of probiotic and clove essential oils had no effect on cutaneous basophils hypersensitivity (CBH) and antibody levels against Newcastle disease virus and avian influenza (P>0.05) but antibody response to sheep red blood cells was higher in the control group which received a diet supplemented with 450 ppm clove essential oils. It can be concluded that probiotic Protexin and 450 ppm clove essential oil can enhance antibody titre but had no significant effect on cellular immunity and antibody response to Newcastle and influenza disease and relative weight of Bursa of Fabricius, thymus and spleen.

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