Ali OLFATI1*, Ali MOJTAHEDIN2
1Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, IRAN
2Assistant Professor of Physiology, University of Mohaghegh Ardabili, Ardabil, IRAN
Corresponding author: A.firstname.lastname@example.org; Tel: +989195966273;
Abstract. Heat stress (HS) is known to have adverse effects on growth performance and immune system. Medicinal plants are utilized as growth and immunity promoter. Thus, 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 submitted to HS. Broilers were divided into five groups; 1) the chicks fed with basal diet and reared under thermoneutral condition; 2) the chicks fed with basal diet and submitted to HS condition; 3, 4 and 5) the broilers fed with basal diet containing 100, 150 and 200 mg TEO/kg of diet and exposed to HS. Broiler chicks were evaluated for antibody titre against sheep red blood cell (SRBC) on 35 and 42 days. Birds were also bled (42 d) to evaluate the blood biochemical variables. HS increased feed conversion ratio and mortality and decreased body weight gain and feed intake (P<0.05). Dietary inclusion of TEO at levels of 150 and 200 mg/kg alleviated negative effects of HS on growth performance (P<0.05). HS increased the serum concentrations of cholesterol, triglycerides, corticosterone, malondialdehyde and heterophil count (P<0.05) and also reduced antibody titre against SRBC, lymphocyte count and lymphoid organs weight (P<0.05). Dietary inclusion of TEO at levels of 150 and 200 mg/kg alleviated negative effects of HS on blood biochemical variables and immune responses (P<0.05). TEO at levels of 150 and 200 mg can be advised for improving the growth performance and immune responses of broiler chicks in hot regions.
Keyword: broiler chicks, heat stress, humoral immunity, lymphoid organs.