Jovana Čukuranović Kokoris - Department of Anatomy, Faculty of Medicine, University of Niš, Niš, Serbia
Zoran Ružić - Department of Veterinary Medicine, Faculty of Agriculture, University of Novi Sad, Novi Sad, Serbia
Zdenko Kanački - Department of Veterinary Medicine, Faculty of Agriculture, University of Novi Sad, Novi Sad, Serbia
Slobodan Stojanović - Department of Veterinary Medicine, Faculty of Agriculture, University of Novi Sad, Novi Sad, Serbia
Smiljana Paraš - Department of Cell Biology, Faculty of Natural Sciences and Mathematics, University of Banja Luka, Banja Luka, Bosnia and Herzegovina
Verica Milošević - Department of Anatomy, Faculty of Medicine, University of Niš, Niš, Serbia

The aim of this study was to examine the effects of heat stress (HS) on the pituitary-adrenal axis and whether the treatments with early-age thermal conditioning (ETC) and vitamin C, alone and in combination, could have a beneficial effect in alleviating these effects. For the experiment, ۴۰۰ one day-old broilers (both sexes) were used, being divided into four groups. The first group was the control (K), the second group (C) consisted of broilers which received vitamin C from the ۲۲nd to the ۴۲nd day via water in the amount of ۲.۰۰ g L-۱, in the third group (T), broilers were exposed to ETC for a period of ۲۴ hr at a temperature of ۳۸.۰۰ ± ۱.۰۰ ˚C and the fourth group (T + C) was the combination of T and C groups. Immunohistochemically positive adrenocorticotropic hormone (ACTH) cells of broilers in all groups were irregular or stellate and distributed in the periphery and central parts of the pituitary gland, as solitary cells or in clusters. In the T + C group of broilers, a significant increase in the area of ACTH cells (۱۸.۹۱%) and their cores (۲۲.۷۵%), and cortisol level in serum compared to the control group was observed. This reaction of broilers in the T + C group facilitated their adaptation to unfavorable consequences of HS. These results suggest that hypothalamic-pituitary-adrenal axis is stimulated after the exposure to chronic HS, enabling successful adaptation of broilers to adverse conditions.

Adrenocorticotropic hormone cells, Broiler chickens, cortisol, Heat stress, Immunohistomorphometry