الفهرس 
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Abstract
Two separate experiments were conducted in a private poultry farm located in San-El-Hagar city, Sharkia Governorate, Egypt. The first experiment, the objective of this study was to assess the effect of dietary supplementation of Nigella sativa oil (NSO) as a growth promoter in broiler diets. A total number of 300 unsexed, one-day-old Arbor Acre broiler chicks were randomly divided into 5 treatment groups (60 chicks/group). Each group was divided into five replicates with 12 chicks per replicate. The 1st group was fed on the basal diet with no additives (control). The 2nd group was fed on the basal diet supplemented with oxytetracycline antibiotic (OTC) at level of 50 ppm. The 3rd, 4th and 5th groups were fed on the basal diet supplemented with 500, 1000 and 1500 ppm NSO, respectively. Birds fed on 1500 ppm NSO diet showed the heaviest body weight (BW) at 14, 28 and 42 days of age. Feed conversion ratio (FCR) was significantly improved during all ages with the dietary inclusion of OTC and NSO compared with the control group. The relative weight of the spleen was significantly increased by the NSO addition at different levels; however, relative weights of the thymus and bursa were not significantly altered among the different treatments. Total bacterial count, total yeast and molds count, E. coli and salmonella spp. counts were significantly reduced, while the total lactic acid bacteria count was increased in OTC and NSO supplemented groups as compared to control groups. The second experiment, this study aims to investigate the effect of supplementing dietary cinnamon oil (CO) into broiler chicken diets on growth performance, carcass traits, haemato-biochemical parameters, immune function, antioxidant status, and caecal microbial count. Three hundred one-day old broilers were distributed randomly, with five replications, into 5 groups (12birds/replicate). Dietary treatments comprised the basal diet (control group), and the basal diet supplemented by 10 mg/kg avilamycin or 500, 1000 and 1500 mg/kg of CO. Results indicated that birds from CO-treated groups had higher BW, weight gain and improved FCR as compared with the control group. Also, birds from CO supplemented groups had lower total cholesterol, triglycerides, low-density lipoproteins than those from the control group; the lowest values were recorded in the group treated with 500 mg/kg CO. Treatment with CO increased the relative weight of the spleen, thymus, bursa of Fabricius and plasma content of IgM when compared to the control and the antibiotic-treated groups. In broiler chicks fed CO a significant decrease in caecal total microbial count, total yeast and mold count, Escherichia coli, and Salmonella was noted in comparison with the control group but was similar to animals from antibiotic-treated group. The count of lactic acid bacteria increased in the caecum of chickens fed CO in comparison with those from the control group; the lowest level was observed in the antibiotic group. So, from the above results we can conclude that, the supplementation of broiler diets NSO or CO (upto 1500 ppm) has had beneficial effects on growth and carcass characteristics, immune function, antioxidant status and caecal microbial count. So, NSO or CO could be used as a natural alternative feed additive to promote gut health and consequently improve growth performance of broiler chicken instead of antibiotic growth promoters.