Genetic improvement of egg laying traits in Fayoumi chickens bred under conditions of heat stress through selection and gene expression studies.Thermal stress has been shown to result in decreased egg production, decreased eggshell quality, and ultimately millions of dollars in losses to the industry.  In the present study, day-old Fayoumi chicks were raised either under normal temperature (control) or conditions of thermal stress (the heated group).  Furthermore, the reduction in egg production and eggshell strength as a result of heat stress declined from one generation to the next in birds selected for good heat tolerance, and an inverse relationship was observed between the OC-17 and eggshell strength.  Additionally, levels of HSP90 and gene expression increased in the two successive generations, indicating that both productivity and heat tolerance were enhanced due to selection in birds raised under conditions of thermal stress.  Thus, desirable traits such as improved heat tolerance in producing lines were observed in Fayoumi chickens exposed to conditions of thermal stress via selection. 
THERM