Ninety six unsexed one-day old, Ross 308 broiler chicks, were randomly divided into 4 treatment groups. Each treatment had 3 replicates with 8 chicks each. The chicks of each replicate were allocated in a cage. The basal experimental diets had 24 and 22% crude protein and 3009 and 3135 Kcal ME/kg diet for the starter and the grower diet, respectively. The experiment was included four treatments, treatment 1; chicks were fed on basal diet without any addition (control). Whereas, in treatments 2, 3 and 4 chicks were received 0.5%, 1.0% and 1.5% marjoram leaves powder (Origonum marjorana), respectively.
Supplementing the broiler diet with marjoram leaves powder increased significantly (P<0.05) Live body weight (BW) at 21 and 42 days of age, daily body weight gain (BWG) at all periods and globulin than the control group. Moreover, addition of marjoram improved (P<0.05) feed conversion ratio (FCR) at all periods and decreased significantly (P<0.05) daily feed intake (FI) at 4-6 and 0-6 weeks of age, albumin and albumin/ globulin ratio in the treated groups as compared with control group. Conversely, supplementing the broiler diets with marjoram leaves powder had no significant effect on feed intake (FI) at 0-3 weeks of age, hematocrit HCT, hemoglobin, glucose, total protein, cholesterol , LDL cholesterol, HDL cholesterol, heterophils (H), lymphocytes (L), monocytes, H/L ratio, averages of serum haemagglutinin antibody (Ab.) titers against SRBC's at 6 weeks of age and spleen and bursa percentages. Overall, these data indicate that, supplementing marjoram into the broiler diets improved productive performance but it did not affect the immune response.