Feed additives and nutritional supplements are attaining importance nowadays in the poultry industry, as well as in healthcare systems, because of their wide spectrum of beneficial impacts, such as promoting growth and production, immune enhancement and health protection. Moreover, non-nutritional factors such as hygiene, processing of feed ingredients, ambient temperature, animal health and genetic makeup have an impact on animal performance. The poultry industry has achieved tremendous progress in its production system during the last 50 years through improvements in genetic makeup, proper management and advancements in nutritional science. The use of feed additives has increased and contributed to the success achieved in current broiler production . Feed additives are generally considered materials used to enhance the effectiveness of nutrients and exert their effects on improving poultry performance . There are a number of feed additives used in poultry feed, such as antibiotics, probiotics, oligosaccharides, enzymes and organic acids . They are included in the diet of poultry and animals for promoting growth through their potential effect in increasing feed intake. Also, low levels of additives in poultry feed can contribute to an increase in the production of poultry protein for human consumption, which in some instances can decrease the cost of animal and poultry production . There has been an increase in the supplementation of probiotics in poultry nutrition . Subtherapeutic antibiotics are typically used to prevent disease and aid in BW gain. Some consumers view subtherapeutic antibiotics negatively. This is because of growing evidence that antibiotic resistance genes could be transmitted from animals to humans. Today, many fast-food chains and restaurants state that they do not accept meat from chickens grown with antibiotic growth promoters . Furthermore, the Food and Drug Administration (FDA) is putting more rules in the United States for medically important products used in both human and animal nutrition. While the use of AGPs plays a role in poultry production and phasing out their use can decrease finishing weights, this coupled with the negative effects of heat stress (HS) can decrease production substantially. Heat stress can be detrimental in tropical and subtropical regions of poultry production. In the United States alone, HS results in an estimated total annual economic loss of $128 to $165 million for the poultry industry. Eleven states in the United States are considered subtropical. Out of those 11 states, ten are in the top 15 for US broiler production. These ten states make up 73% of total broiler production in the United States. Probiotics have shown many beneficial properties with the ability to improve immunity, intestinal structure and gut barrier function in broilers. These factors can improve digestion and absorption, which ultimately can improve performance results during HS.