The Effects of Different Levels of Dried Aerial Parts Powder and Extract of Pennyroyal­ (Mentha pulegium) Medicinal Plant on Performance, Egg Quality, Blood Biochemical and Immunity Parameters of Laying Hens

This experiment was conducted to evaluate the effects of different levels of dried aerial parts powderand extract of pennyroyal­ (Mentha pulegium) medicinal plant on performance, egg traits, blood biochemical and immunity parameters of laying hens. Two-hundred-fifty-two Hi-line (W36 strain) laying hens from 46 until 58 weeks of age were used in a completely randomized design in 7 treatments and 3 replicates (12 birds per replicate). The treatment groups consisted of a control group (1) with no dried aerial parts powder or extract of pennyroyal­ supplementation, and experimental groups 2, 3 and 4 contained 0.5%, 1% and 1.5% of pennyroyal­ powder respectively, whereas experimental groups 5, 6 and 7 contained 0.1%, 0.2% and 0.3% of pennyroyal­ extract, respectively. Using different levels and forms of pennyroyal­ significantly affected the performance, egg traits, blood biochemical and immunity parameters of laying hens (P