SINDH UNIVERSITY RESEARCH JOURNAL (SCIENCE SERIES) Effect of Heat Stress and Ascorbic Acid on Gut Morphology of Broiler Chicken A. R. JAHEJO ++ I. H. LEGHARI, A. SETHAR*, M. N. RAO, M. NISA, G. H. SETHAR** Department of Poultry Husbandry, Faculty of Animal Husbandry and Veterinary Sciences, Sindh Agriculture University, Tandojam, Pakistan. Received 17 th January 2016 and Revised 18 rd August 2016 1. INTRODUCTION Heat stress is an environmental condition which is adversely affecting poultry industry worldwide. A broiler chicken is sensitive to heat stress due to large size and absence of sweat glands along with rapid metabolism, and high body temperature. Researchers are investigating the effect and solution of high environmental temperature on the performance of the meat type of. Pakistan’s most of the farming is located at tropical zone and thus our poultry industry suffers from the ambient temperature of May to September. Heat stress occurs when high temperature of the environment accompanies high humidity during these months and which adversely effects the productivity of broiler chicken and make broiler rearing conditions risky and not profitable (Fouad, et al. 2016). Broilers have versatile heat regulatory system when they are exposed to high ambient temperature, their body temperature increases more than the normal body temperature and the corticosterone stored in adrenal cortex are released into the blood circulation to help broilers increase metabolism (Ready, 2000). This hormone might cause cell mediated and humoral immunity failure because changes in the plasma concentrations of corticosteroids and ACTH affected the lymphoid tissues; for example, a diminution in the mass of the spleen, thymus and bursa of fabricius might be observed. Moreover, glucocorticoids cause dissolution of lymphocytes which may lead to lymphopenia and more heterophils are released in the blood circulation but heir phagocytic and bactericidal activities may decreases. Thus, there is a need to improve the thermo tolerance of the broiler chickens in the hot climatic conditions without affecting the production of meat purpose broiler chickens. Nutritional strategy in the heat stress conditions plays crucial part in reducing the negative impact of heat stress. The offered diet should fulfill the requirements of birds for proteins, electrolytes and energy (Balnave 2004) . Ascorbic acid is being used largely in the poultry industry during heat stress due to its anti-oxidant effect, which neutralizes the free radicals which are produced during the environmental stress (Ramnath et al., .2008). Broilers themselves can synthesize their own ascorbic acid but its quantity is insufficient to reduce the free radicals (Maurice et al., 2002). Review of literature shows not enough work has been carried on previously on the relationship among environmental stressors (such as heat stress etc) on the gut microbial environment in chicken. A broiler subjected to heat stress has been reported to altered morphology and altered microbial community in the intestinal tract. Under heat stress conditions, increased concentrations of reactive oxygen species (ROS) occur which lead to increased intestinal permeability, which in turn facilitates the translocation of bacteria from the intestinal tract (Lara and Rostagno 2013). Keeping in views the importance of commercially used ascorbic acid, the research trials were conducted to Sindh Univ. Res. Jour. (Sci. Ser.) Vol. 48 (4) 829-832 (2016) Abstract: The experiment was conduct d to evaluate the effect of heat stress and ascorbic acid (AA) on the gut morphology of broiler chickens. In this regard, macro and micromorphomatric study of the three segment of intestine such as duodenum, jejunum, ilium were performed along with the nutrients retention in the intestine. For this purpose 180 birds were purchased and divided into four equal groups i.e. normal temperature with and without AA, high temperature with and without AA supplementation. Our finding showed that birds reared under heat stress free environment and provided with AA showed significantly higher weight gain and size of intestinal parts along with higher nutrient retention than all other groups (P<0.05). Moreover, weight and length of Duodenum, jejunum and ileum was observed significantly (P<0.05) lower in heat stress control group than the AA supplemented group. Thus it was concluded that AA supplementation improves the villi size and nutrients digestibility when supplemented in normal temperature, whereas significantly (P<0.05) improves the weight and length of intestine when supplemented under higher temperature. Keywords: Broilers, Heat Stress, Ascorbic acid, Gut Morphology ++ Correspondence Author: imdadleghari@hotmail.com *Livestock & Fisheries Department, Sindh Agriculture Growth project, Livestock Component, Government of Sindh @ Hyderabad, **Al-Amiri Hospital, Kuwait City, Kuwait.