and diet supplemented with 36 mg/kg essential oils had no effect on serum total cholesterol of laying hens (Özek et al., 2011). And serum calcium concentration was significantly decreased by dietary supplementation of bergamot oil (1.5 ml/kg) to laying hens during the late laying period (75 week old) (Bölükbas¸ i et al.,2010). For clear conclusion, further systematic studies might be considered to elucidate the effect of peppermint leaves at different stages of production in laying hens