Antibiotics as growth promoters which had used for long terms in livestock and poultry industries are restricted or banded because of the microbial resistance in animals as well as humans. Within the last few years using the prebiotics, probiotics, herbal extracts, enzymes, organic acids and some other natural products is going to be substitute for antibiotics in order to improve immune system in humans and animals. Today, there is increasing interest in use of natural antioxidants such as rosemary (Rosmarinus officinalis) and its products, flavonoid and tocopherol extracts for food preservation. Because these natural antioxidants avoid undesirable health problems that may arise from using of synthetic antioxidants, such as butylatedhyd roxyanisole and butylatedhyd roxytoluene which may have toxic effects to the consumers. The purpose of this study was to determine the effect of rosemary (Rosmarinus officinalis) and its products on the immune response of Japanese quail to influenza killed vaccine virus. One hundred and sixty day-1 Japanese quail were used in this experiment. They were randomly divided to four treatments with 4 replicates of 10 chicks per replicate. The experimental groups including: rosemary powder (5000 ppm/kg feed), essential oil of rosemary (100 ppm/kg feed), ethanolic extract of rosemary (100 ppm/kg feed), and control group. At day 21, Avian influenza (H9N2) killed vaccine (Razi Institute, Karaj, Iran) were injected subcutaneously to all of the experimental chicks. The immune response was assessed by hemagglutination inhibition (HI) test. The HI titers against influenza vaccine were determined on serum samples of the same birds at day 42. There was significant difference (P<0.05) between experimental groups in antibody production against AI vaccine. The rosemary powder numerically produced the highest antibody titer to AI and the lowest concentration titer was related to control group. The present findings suggest that dietary rosemary and its products could improve immune response in Japanese quails.

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