Effects of dietary graded levels of cinnamon essential oil and its combination with bamboo leaf flavonoid on immune function, antioxidative ability and intestinal microbiota of broilers

Abstract Cinnamon essential oil (CEO) and its combination with bamboo leaf flavonoid (BLF) have been shown to exhibit an additive antibacterial effect in vitro, but their functions in broilers were not clear. An experiment was conducted to investigate the effects of dietary graded levels of CEO and its combination with BLF on the growth performance, immune responses, antioxidative ability, and intestinal morphology and microbiota of broilers fed a corn-soybean meal basal diet. A total of 576 1-d-old Arbor Acres commercial male broilers were randomly allotted to 9 treatments with 8 replicates of 8 birds each in a completely randomized design. Birds were fed on a basal corn-soybean meal diet (control, without plant extracts and antibiotics), or the basal diet supplemented with 50 mg of aureomycin kg−1, 50, 100, 200, 400, or 800 mg of CEO kg−1, a combination of 100 mg of CEO and 16.7 mg of BLF kg−1, or a combination of 200 mg of CEO kg−1 and 33.3 mg of BLF kg−1 for 42 d. Dietary treatment affected (P 0.16) on all other measured indices. The addition of 400 mg of CEO kg−1 or a combination of 200 mg CEO kg−1 and 33.3 mg BLF kg−1 increased (P