Antioxidant properties of the fennel essential oil nanoemulsion: Effect on European production efficiency factor, blood metabolites, immune system and cecal microbial population of heat stressed broiler chickens

In this study, the antioxidant properties of fennel essential oil nanoemulsion (FEON) and its effect on European production efficiency factor, blood metabolites, immune system, and cecal microbial population of broiler chickens under heat stress conditions were investigated. Two hundred one-d-old Ross broiler chickens were arranged in a completely randomized design with 5 treatments, 4 replicates, and 10 birds each. The birds were fed on a basal diet (control), basal diets supplemented with 50, 100, and 200 mg kg-1 fennel essential oil nanoemulsion (FEON50, FEON100, and FEON200) and 200 mg kg-1 fennel essential oil (FEO). The results showed that compared with FEO, all concentrations of FEON had greater antioxidant activity (P≤0.001). During the starter, grower, and the whole phase of the rearing period, the performance indicators such as the European production efficiency factor and European broiler index, were not affected by dietary treatment. Further, blood total cholesterol and low-density lipoprotein contents were significantly decreased by supplementation of broiler diets with FEON (P≤0.01). Primary antibody titer against sheep red blood cells (SRBC) was affected by the addition of FEO and FEON50 into broiler diets (P≤0.05). Moreover, the Lactobacillus population of cecal content was significantly increased and coliform populations were decreased when FEON was added to the diet. The Escherichia coli population of cecal content decreased when FEO and FEON were supplemented into the diets (P≤0.05). The jejunal, ileal, and cecal digesta pH decreased significantly in the FEON50 treatment. The results of this experiment showed that under heat stress conditions, supplementation of broiler chickens' diets with FEON can enhance primary humoral immunity and improve the broiler gut health and FEON50 was the optimal level.