Effect of thymol and carvacrol feed supplementation on performance, antioxidant enzyme activities, fatty acid composition, digestive enzyme activities, and immune response in broiler chickens

This trial was conducted to evaluate the effects of dietary supplementation of phytogenic product containing an equal mixture of thymol and carvacrol at 4 levels (0, 60, 100, and 200 mg/kg of diet) on performance, antioxidant enzyme activities, fatty acid composition, digestive enzyme activities, and immune response in broiler chickens. Each of the 4 diets was fed to 5 replicates of 12 chicks each from d 0 to 42. The inclusion of thymol + carvacrol linearly decreased (P <0.05) feed intake, but the highest (P <0.05) BW gain (ADG) and feed efficiency was observed in broilers offered 200 mg/kg of phytogenic product. The phytogenic product linearly increased (P <0.05) superoxide dismutase and glutathione peroxidase activities and decreased (P <0.05) malondialdehyde level in thigh muscle at d 42 and serum and liver at d 24 and 42. Total saturated fatty acids were depressed (P <0.05) and total polyunsaturated fatty acid and n-6 were linearly increased (P <0.05) in serum and thigh by the inclusion of phytogenic product compared with the control diet. Supplementation with thymol + carvacrol also increased intestinal and pancreatic trypsin, lipase, and protease activities in 24-d-old (linear, P <0.05) but not in 42-d-old birds. Thymol + carvacrol modified (linear, P <0.05) immune response by increasing hypersensitivity response, total and IgG anti-sheep red blood cell titers, and decreasing heterophil to lymphocyte ratio compared with the control group. However, hematological parameters and lymphoid organ weight were not affected by thymol + carvacrol. Thus, feed supplementation with thymol + carvacrol enhanced performance, increased antioxidant enzyme activities, retarded lipid oxidation, enhanced digestive enzyme activities, and improved immune response of broilers.