Effect of Peppermint (Mentha piperita) Powder on Immune Response of Broiler Chickens in Heat Stress

To study the effect of different levels of peppermint (Mentha piperita) plant powder, on immune system of broilers under heat stress condition, 192 one-day old chickens (Ross, 308) were randomly allocated to 4 dietary treatments with 4 replicates of 12 chicks each, using a completely randomized design. The four groups were characterized by a basal diet (control), basal diet supplemented with 1 and 2 percent peppermint powder and basal diet supplemented with 300 mg/kg vitamin E. Heat stress was created by setting room temperature at 34 ˚C for 8 hour/day from the 35th to the 42nd day of experiment. Results showed differences (P