الفهرس 
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Abstract
The objective of this review was to compile current knowledge and evidence from literature about the effects of heat stress (HS) on poultry performance and behavior and their alleviation methods. Controlling environmental conditions is crucial to successful poultry performance and welfare. Heat stress is one of the most important environmental stressors challenging poultry production worldwide. The HS in poultry reduced their performance and production. Heat stress suppresses immune function by inhibiting total white blood cell counts and antibody level. High ambient temperatures will increase water intake. Chickens drink four times more at 38°C as compared to 21°C. Broilers subjected to chronic HS had significantly reduced FI, lower BW, and higher feed conversion ratio at 42 days of age. Heat stress induces marked alteration in the biochemical variables such as serum cholesterol and triglycerides in chickens. Meanwhile, HS affects the mineral balance, plasma electrolyte concentration, and plasma protein concentration in poultry birds. Excess free radicals produced during oxidative stress damage all the components of the cells including proteins, lipids, and DNA. Vitamins and mineral supplementation has been determine to decrease mortality and improve growth performance of poultry birds during heat stress as because heat stress increases excretion of mineral from body and decreases serum concentrations of vitamins and minerals. In conclusion, changes in the microbial community structure in the intestinal tract of broilers subjected to heat stress have been reported decrease feed intake, decrease egg production, egg weight, shell quality, albumen height, growth, hatchability, and fertility in roosters increase immunosuppressant, increase cannibalism increase mortality.