Dietary Inclusion of Thyme Essential Oil Alleviative Effects of Heat Stress on Growth Performance and Immune System of Broiler Chicks

This study was conducted to evaluate the effects of dietary inclusion of thyme essential oil (TEO) on growth performance and immune responses of broiler chicks subjected to heat stress (HS). Broilers were divided into five groups; group 1) chicks fed with basal diet and reared under thermoneutral condition; group 2) chicks fed with basal diet and subjected to HS condition; and groups 3, 4 and 5) chicks exposed to HS and fed with basal diet containing 100, 150 and 200 mg TEO/kg of diet, respectively. Broiler chicks were evaluated for antibody titre against sheep red blood cell (SRBC) on 35 and 42 days. Broiler chicks were bled at the end of the experiment (day 42) for blood metabolites measurements. Heat stress increased feed conversion ratio and mortality and decreased body weight gain and feed intake (P<0.05). Dietary inclusion of TEO at 150 and 200 mg/kg of diet alleviated negative effects of HS on growth performance (P<0.05). Heat stress increased the serum concentrations of cholesterol, triglycerides, corticosterone, malondialdehyde and heterophil count (P<0.05) and reduced antibody titre against SRBC, lymphocyte count and lymphoid organs weight (P<0.05). Dietary inclusion of TEO at 150 and 200 mg/kg of diet reversed negative effects of HS on blood biochemical metabolites and immune responses (P<0.05). In conclusion, thyme essential oil supplementation at 150 and 200 mg kg of diet can be advised for improving the growth performance and immune responses of broiler chicks in heat stress condition.