РУАЭСТ (RUAEST)
HEAT STRESS IN POULTRY. I. DANGER, RELATED PHYSIOLOGICAL CHANGES AND SYMPTOMS (REVIEW)
Data on heat stress in poultry are surveyed in a two-part review. 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. Imangulov et al., 2005). 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, A. Khatoon, 2013), disturbances of endocrine (B.Y.L. Hai et al., 2000; Y.A. Attia et al., 2009) and acid-base (S.A. Borges et al., 2004) balances, impaired antioxidant status, abnormal function of definite organs and mechanisms (P. Surai, T. Fotina, 2010). Heat stress enhances the synthesis of corticosterone, noradrenaline and adrenaline which suppress releasing and distribution of steroids and gonadotropins, thus activating deregulation mechanisms fundamental for follicular growth and development as well as the ovulation (A. Yakubu et al., 2007; Y. Song et al., 2009; A.O. Oguntunji, O.M. Alabi, 2010). Additionally, the synthesis and releasing of vitellogenin necessary for the deposition of yolk is suppressed (M. Ciftci et al., 2005). 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).