The research was conducted to examine the effects of supplementation of spearmint (Menthaspicata)extractto laying hens’ diet on the performance, egg quality, blood biochemical and immunity parameters of laying hens. In the experiment, a total of 300 of Hy- line (W36) laying hens of 34 weeks of age were used. Hens were divided randomly into five groups and 3 repetitions and fed different level of spearmint as follows for eight weeks. The best result for production percent, FCR,shell thickness and yolk weightwere seen in the group5. Alsothe serum total cholesterol,Triglycerides and LDL concentration were significantly reduced in groups of 4 compared to the control group (P<0.05). But the concentration of serum HDL and glucose were not significantly reduced in groups compared to the control group also using this herb did not show significantly effects on the immune system of laying hens.
