Supplementation of Zinc and Vitamin C in Heat Stressed Broilers

Heat stress is a major threat to the broiler industry in tropical regions, causing huge mortality during summer season. The study examined the efficacy of Zinc and vitamin-C in reducing heat stress of broiler chicks. One hundred and sixty, day-old broiler birds were randomly allotted to four dietary treatments (A, B, C and D) replicated 4 times (10 birds/replicate). Treatment A was control and other were either supplemented Zn (60 mg kg^-1, B), vitamin-C (300 mg kg^-1, C) and Zn + vitamin-C (D). All birds were reared on deep litter system and had ad libitum access to feed and water. Heat stress was induced during the finisher phase by increasing house temperature to 40 ⁰C from 7:00 am to 7:00 pm. Antibody titer was determined using heamagglutination inhibition (HI) and ELISA tests. Blood samples were collected from birds in all groups and smears were prepared to count blood leukocytes. Birds in treatment-D had better (p<0.05) body weight gain and FCR to other dietary treatments and lower feed intake in control treatment. No significant difference was seen in the antibody titer against Newcastle disease (ND), Infectious Bursal disease (IBD), and Infectious Bronchitis (IB) of treated groups and was lowest (p<0.05) in treatment-A. Total leukocyte count (TLC) was significantly reduced however, neutrophil, eosinophil, lymphocyte and monocyte numbers were increased in control group. Difference in the count of these cells among treated groups was non significant. Significantly high mortality was observed in control group with apparent symptoms of dehydration. It can be obtained from these findings that strategic dietary supplementation of Zinc and vitamin-C can effectively be used to alleviate the adverse effects of heat stress in meat type chickens. Further research is however warranted to investigate the effect of these feed additives at different levels and strains of broilers.

Keywords: Antibody titer. Broilers. Heat stress. Vitamin C. Zinc.