This study was carried out to determine the effect of different levels of clove essential oil, as a natural growth promoter and probiotic on performance, carcass traits and serum components of broiler chickens. A total of 240 straight run day-old commercial broiler chicks (Cobb 500) were distributed randomly into five groups. Each group was subdivided into four replicates with 12 chicks each. The control diet, diet with pro-biotic protexin®, and diets supplemented with 150, 300 and 450 ppm clove essential oil were fed to the chickens. The results showed that from 11-22 days, feed intake (FI), and body weight gain (BWG) were increased significantly in control group compared to the other groups. However, from 23-42 d and 0-42 days of the experiment, feed intake (FI) and body weight gain (BWG) were increased significantly in broil-ers fed 450 ppm clove essential oil compare to those of control group (P<0.05). Also, clove essential oil at the level of 450 ppm increased feed intake (FI), body weight gain (BWG) and improved feed conversion ratio (FCR) in finisher period (P<0.05). Results show that different levels of clove essential oil and probi-otic had not any significant effect on dressing percentage, abdominal fat and internal organs percentage (liver, heart and gizzard) (P>0.05). The results revealed significant decrease in total cholesterol concentra-tion in diets supplemented with probiotic and 450 ppm clove essential oil at 21 day of age (P<0.05). Total cholesterol concentration, low density lipoprotein (LDL), and cholesterol / high density lipoprotein (HDL) ratio at 42 day of age were significantly improved in probiotic protexin® group compare to those of other groups (P<0.05). In conclusion, dietary supplementation with 450 ppm clove essential oil improved feed intake (FI), body weight gain (BWG), feed conversion ratio (FCR) and decreased total cholesterol concen-tration (P<0.05). Probiotic could decrease serum cholesterol, low density lipoprotein (LDL), cholesterol / high density lipoprotein (HDL) and improve HDL / LDL at day 42 broiler chickens (P<0.05).

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