Effects of heat conditioning and dietary ascorbic acid supplementation on heat shock protein 70 expression, blood parameters and fear-related behavior in broilers subjected to heat stress

ABSTRACT

Background: Heat stress is one of the most important environmental factors. Exposure of broilers to high temperaturecauses signifi cant changes in physiological response. Early heat conditioning induces the heat tolerance of broiler chickensat later growth stage prior to marketing. Ascorbic acid supplementation has been reported to may alleviate the negative effects of heat stress on the performance of broilers. This study was carried out to investigate the effects of heat conditioningand dietary ascorbic acid supplementation on heat shock protein 70 expression, blood parameters and fear-related behaviorin broilers subjected to heat stress.Material, Methods & Results: A total of 320 male broilers were used as the material of this study. Broilers were randomlyassigned to four treatments. Each group contained four replicates with 20 chicks in each pen. Until the 21 days of age, allanimals were raised at comfort temperature. The brooding temperature was maintained at approximately 32oC for the fi rst3 days and then decreased 3oC weekly until 21 days. Broilers in control group were kept under thermo-neutral conditions(24oC) and fed with the basal diet throughout experimental period. Other three groups were exposed to heat stress from22 to 42 days of age. Heat stress was applied by exposing the broilers to a temperature of 35oC for 6 h/day between 1000h and 1600 h. Ascorbic acid supplemented group was fed a diet supplemented with 500 mg of L-ascorbic acid/kg rationand exposed to heat stress from 22 to 42 days of age. Heat conditioned group was exposed to a temperature of 36oC for 24h at the age of 5 days; fed with basal diet and exposed to heat stress from 22 to 42 days of age. Heat stress group was fedwith the basal diet, no subjected to heat conditioning and exposed to heat stress from 22 to 42 days of age. The broilers inheat stress group had higher body temperature, H/L, TI duration, serum corticosterone, glucose...(AU)