Thesis (M.Sc.) - Cairo University - Faculty of Veterinary Medicine - Department of Veterinary Hygiene and Management

This study was carried out aimed to evaluate the impact of some immune-suppressors on bursa of Fabricius indices and on the humoral immune responses against HPAI H5N1, NDV, IBD and IBV vaccines in commercial broiler. Two studies were conducted simultaneously in a commercial broiler farm in Alkhatatba area in Egypt. Each study was composed of four different groups (each 100 commercial broiler birds). Two immunosuppressive factors were compared in each study. Blood samples were collected from 20 birds / group at 4, 14, 21, 28, 35 and 42 days of age and bursa samples were collected by euthanizing five birds / group at 28 and 35 days of age. Serum samples were tested to identify the titers of IBD antibody by ELISA (using two different kits), infectious bronchitis antibody by ELISA, ND and HPAI H5 antibodies were titered using haemagglutination inhibition test. Bursa samples were examined for bursa body weight ratio, index and histopathology. In paper 1 and paper 3, No humoral immune suppression was noticed in the group vaccinated with HVT+IBD vaccine on contrary to a significant humoral immune suppression in IC vaccinated group. In paper 2 and paper 4, groups were exposed to mycotoxins & hard water. General humoral immune suppression was noticed in the group exposed to mycotoxins while for the group exposed to hard water only IB antibody titers was significantly reduced. Results were obtained, statistically analyzed, tabulated and discussed. It was concluded that HVT+IBD preserve the immune capacity of broilers to respond to vaccination programs but require the proper control of mycotoxins to avoid a suppressed vaccine take

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