In the first part presented herein the authors summarized current knowledge on the influence of heat stress on alterations of metabolic and physiological processes in poultry as well as the adverse consequences for livability, growth, development and productivity, being 19.3-28.8 % less, and product quality (M.M. Mashaly et al., 2004; Sh. <...> The level of these alterations depends on strength and durability of the exposure to stressing conditions, on age of birds, type and level of productivity, health status, nutrition program, complex of genetic factors, rearing conditions, etc. (J.O. Ayo et al., 2006; A. Kavtarashvili, T. Kolokolnikova, 2010). <...> Heat stress triggers a wide range of behavioral, physiological and immunological alterations in poultry (J.O. Ayo et al., 2006; P.F. Surai, T.I. Fotina, 2013) as a result of intricate interactions between decreased feed consumption up to 34.7 % (M.M. Mashaly et al., 2004; Z. Abidin et al., 2000; Y.A. Attia et al., 2009) and acid-base (S.A. Borges et al., 2004) balances, A. Khatoon, 2013), disturbances of endocrine (B.Y.L. Hai impaired antioxidant status, abnormal function of definite organs and mechanisms (P. Surai, T. Fotina, 2010). <...> The activity and efficiency of lymphoid organs such as bursa, spleen, thymus are also impaired, the numbers of monocytes, lymphocytes and heterophils are increased (O. Altan et al., 2000; S.M. Naseem et al., 2005) resulting in impaired immune response in poultry (V. Savic et al., 1993). <...> The antioxidant status is decreased resulting in higher levels of oxidative stress when the balance between the production of free radicals and levels of antioxidants able to neutralize them is disturbed (L.T. Kadim et al., 2008). <...> That leads to increased clearance of carbon dioxide necessary for synthesis of calcium carbonate for eggshell formation, followed by subsequent increase in blood pH and respiratory alkalosis, the overall disturbance of acid-base balance (R.G. Teeter et al., 1985; A.Sh. <...> Heat stress triggers a wide range of behavioral, physiological and immunological changes in poultry, which leads to decrease in feed consumption, «Heat stress in poultry. <...> Sharp temperature rise may lead <...>