Anticoccidial activity of essential oils containing eugenol against Eimeria tenella in broiler chickens

The development of alternative therapies to treat chicken coccidiosis has become a hot topic because of the widespread use of conventional medicines. This study aimed to investigate the effectiveness of eugenol in treating Eimeria tenella infection in broilers. Broiers, at the age of 14 d, were orally infected with sporulated Eimeria tenella oocysts, and then, eugenol essential oil was added to chicken feed at three different dosages (0.1, 0.2 or 0.4 g/kg). The anticoccidial effects of eugenol essential oil were assessed using the anticoccidial index (ACI). As a result, eugenol exhibited a moderate anticoccidial effect, with an ACI of 167.37 at 0.2 g/kg. After eugenol treatment, the expression of occludin in the epithelial cells of the chicken cecum was significantly greater (P < 0.05) than that in the epithelial cells of the nontreated control (IC) group. The proportion of intestinal Lactobacillus_agilli increased. Eugenol therapy dramatically increased the activity of superoxide dismutase. After high-dose treatment, the expression of the proinflammatory factors IL-1β and IL-6 significantly decreased, while the expression of the cytokines IL-4 and IFN-γ significantly increased. The safety of eugenol essential oil was evaluated at the 1, 3 or 6 recommended doses. Overall, no significant differences were detected in the blood tests or serum biochemistry of the chickens between the treatment groups and the control group. As a result, eugenol essential oil can cure chicken coccidiosis by improving the intestinal microbial structure in the chicken cecum and decreasing the cecum's inflammatory reactions, thus strengthening immune function and eventually demonstrating anticoccidial properties.