Different essential oils in diets of broiler chickens: 2. Gut microbes and morphology, immune response, and some blood profile and antioxidant enzymes

A study was conducted to evaluate the effect of three essential oils with different main chemical structures, i.e., cinnamon bark oil (CNO), clove bud oil (CLO) and ajwain seed oil (AJO) as an alternative to antibiotic growth promoter (AGP) on intestinal health, immune response and antioxidant status in broiler chickens. Four hundred one-day-old broiler chicks were randomly divided into five dietary groups comprising of eight replicates (n = 8) in each group. Each replicate contained ten chicks. Five dietary groups consisted of: 1) a basal diet (control; without any antibiotic and essential oils); 2) the basal diet + bacitracin methylene disalicylate added at a dose of 50 mg/kg diet (AGP); 3) the basal diet + CNO at 300 mg/kg diet (CNO); 4) the basal diet + CLO at 600 mg/kg diet (CLO); and 5) the basal diet + AJO at 400 mg/kg diet (AJO). Both AGP and CNO significantly increased the villi height in duodenum (P = 0.004), jejunum (P = 0.008) or ileuim (P = 0.003) compared with the control. The counts of Escherichia coli in pre-caecal contents decreased (P = 0.006) in the groups receiving AGP and CNO and the counts of Clostridium spp. decreased (P = 0.029) in the AGP group compared with the control. Population of Lactobacilli spp. was not affected (P = 0.39) by any diets. Antibody titers against Newcastle disease virus increased with CNO, CLO and AJO supplementation (P < 0.001) compared with the control and AGP. The concentrations of cholesterol in serum reduced (P = 0.030) in CNO, CLO and AJO groups compared with the control and AGP groups. Supplementation of CNO and CLO increased (P = 0.001) the superoxide dismutase activity in serum compared with the AGP. In conclusion, supplementation of CNO could be more advantageous than the AGPs in diets due to its combined beneficial effects on immune response, gut health, antioxidant status and blood cholesterol in broiler chickens.