Al-Abbas, Bushra Hadi Sheetah2022-05-182022-05-1820141589https://drepo.sdl.edu.sa/handle/20.500.14154/3736BSTRACT The aim of this study was to investigate the effect of thermal manipulation (TM) during embryonic days (ED) 12-18 on hatchability, growth performance and on mRNA levels of Hsp90 and Hsp60 and HSF-1 in muscle, heart and brain during embryogenesis and during thermal challenge (TC) at day10 and 28 post-hatched. One thousand five hundred fertile chicken eggs were divided randomly into four groups: control group (37.8°C), TM1 (39°C for 9h), TM2 (39°C for 12h) and TM3 (39°C for 18h). Chicks frenThesis