Heat stress is one of the major problems of tropical and subtropical areas of the world, adversely affecting the production performance of poultry. Heat stress suppresses broilers immunity against disease, body weight gain and increases mortality rate in the flock. The avian gastrointestinal tract is populated by a diverse and dynamic microbiota, generally considered important for host nutrition and immunity. About 300 to 500 bacterial species reside broilers gut. The key functions of the gut microbiota in host health and well-being includes nutrients digestion and absorption,and significant...