The effects of using different levels of lemon balm (Melissa officinalis L.) medicinal plant on performance, egg traits, blood biochemical parameters and Immunity cells of laying hens

This experiment was conducted to evaluate the effects of different levels of Lemon balm (Melissa officinalis L.) medicinal plant dried aerial part powder on performance, egg traits, blood biochemical and Immunity cells of laying hens. 180 laying hens (W36 strain) from 46 until 58 weeks of age were used in a completely randomized design in five treatments (0, 0.5, 1, 1.5 and 2%) and three replicates (12 birds per replicate). Using different levels of lemon balm significantly affected the performance, egg traits and blood biochemical parameters of laying hens (p < 0.05). The lowest feed conversion ratio (3.1), the highest egg production (56.85%) and egg mass (35.51 g/hen/day) were observed in Treatment 2 (0.5% lemon balm); the best yolk index (5.17) was obtained in Treatment 4 by using 1.5% of lemon balm medicinal plant whereas the highest Haugh unit (87.91) obtained in control group. The lowest (188.22 mg/dl) and the highest (280.22 mg/dl) amounts of blood glucose were observed in Groups 1 and 2. The results showed that there are no significant differences between treatments on blood immunity cells levels, but numerically the highest percentage of lymphocytes (86.67%) and the lowest percentage of hetrophiles (11%) and the lowest ratio of H/L (0.132) were observed in Treatment 2 by using 0.5% of lemon balm. The overall results showed that the use of 0.5% of lemon balm medicinal plant in the diets of laying hens have positive effects on their performance, egg traits, blood biochemical parameters and Immunity cells.