AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com/www.ijaronline.in *Corresponding author’s e-mail: suraj_amrutkar@rediffmail.com. Indian J. Anim. Res., 50 (1) 2016: 35-40 Print ISSN:0367-6722 / Online ISSN:0976-0555 Influence of different tropical stress conditions on biochemical parameters in various broiler strains S.A. Amrutkar, V.K. Saxena and Simmi Tomar Central Avian Research Institute, Izatnagar-243 122, India. Received: 10-10-2014 Accepted: 16-02-2015 DOI: 10.18805/ijar.8562 ABSTRACT The present experiment was conducted to study the effect of different tropical stress conditions on biochemical traits in various broiler strains during 3 to 4 weeks of age. Introgressing some important major genes likes Naked neck (Na) and Frizzle (F) into broiler germplasm may substantially improve the heat tolerance. Hence, the experiment was designed to evaluate three indigenously developed broilers viz. CARIBRO-Tropicana (Naked neck and Frizzle gene bearing), CARIBRO- Mritunjai (Naked neck gene bearing) and CARIBRO-Vishal (Normal plumaged) under different THI (i.e. 72, 85 and 91) for 4 hours daily for 7 days. Total 324 broiler chicks (i.e. 36 chicks in each group) of 3 weeks of age were used in this study. The changes in blood biochemical parameters (i.e. Na, K, Glucose and ACTH) were examined in these experiments at 0 th , 3 rd and 7 th into exposure trials. The glucose, ACTH were observed lowest in frizzle and highest in normal plumaged birds under different THI. In experiment Na and K were observed higher in Frizzle and lowest in normal plumaged birds under different THI. The CARIBRO-Vishal showed highest stress as compared to other group. Higher the THI more severe was the effect on the traits. During the 7 day of exposure trial, birds of all the genetic group exhibited the phenomenon of acclimatization as reveled by the averages of various traits at different days into the exposure. Key word: ACTH, Biochemical traits, Broiler strains, Glucose, Tropical stress. INTRODUCTION The utilization of major genes for broiler production under tropical conditions exudes much enthusiasm among the poultry breeders. The important major genes are Naked neck (Na), Dwarf (dw) and Frizzle (F). These genes are located on Autosomes and get inherited in Mendelian fashion. Introgressing some important major genes into the poultry germplasm may substantially improve the heat tolerance ability of broilers without reducing their economic performance. Some major genes results in reduction of feather cover while other exerts their effect by decreasing the metabolic heat output (Merat et al., 1986; Cahaner and Leenstra, 1992). Involvement of endocrine system in stress regulation comprised of hypothalamus-pituitary-adrenal axis (HPA) (Seyle, 1956). It is characterized by adrenal cortical hypertrophy, increased synthesis and release of adrenal glucocorticoids, known as corticosterone in bird. The endocrine mechanism of stress regulation is started with the stimulation of hypothalamus and release of ACTH from anterior pituitary which causes the increase of adrenal cortical steroid secretions. Continuous stimulation to adrenal cortex leads to chronically high level of corticosteroid hormones. This hormone is responsible for the formation of glucose from the body reserve of carbohydrates, lipids and proteins. MATERIALS AND METHODS The CARIBRO-Mritunjai (Necked neck plumaged), CARIBRO-Tropicana (Naked neck and Frizzle plumaged) and CARIBRO-Vishal (normal plumaged) broiler chicks developed at Experimental Broiler Farm, C.A.R.I., Izatnagar, were used in this study. Fertile eggs were collected at Experimental Broiler Farm for incubation. Total of 36 chicks (three weeks old) of CARIBRO-Mritunjai, CARIBRO-Tropicana and CARIBRO- Vishal each, for each exposure trial were used. The chicks were reared up to 3 weeks of age at Experimental Broiler Farm (EBF) under uniform nutrition and management. The chicks were reared at litter with ad lib feeding of starter ration. At three weeks of age the chicks were shifted to Psychometric chamber for exposure under particular THI for a period of 7 days. Three weeks old chicks (36) of each germplasm were used in this study in each exposure trial totaling to 108 chicks of each genetic group