Present experiment was performed to study the effects oforegano oil (Origanum sp.)medicinal plant on performance,blood biochemical and immunity parameters of broiler chickens. During the experiment 400 chicken broilers were divided in four experimental groups with five repetitions: control group (C) without any oregano oil, group 1 (G1) received 100 ppm of oregano oil, group 2 (G2)with 150ppm of oregano oil, grop3(G3) received 200 ppm of oregano oil. From 1 day to 42 days, the highest amount of body weight gain and the lowest level of FCR were observed in the groupG3 but the best result for daily feed intake was in G2 and the lowest group was observed in control group. The lowest percent of abdominal fat was observed in experimental group 2 and the highest percent of breast was in experimental G3.The results showed that using oregano oil (Origanum sp.) in chickens diet had not significant effects on on blood biochemical parameters and immune system of broiler chickens (p>0.05).
