Abstract
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.
Key words: Blood metabolites, egg traits, laying hens, Melissa officinalis L., performance.
