الفهرس 
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Abstract
The present study aimed to investigate the effect of oral administration of egg yolk antibody (IgY) against enteric infection in broiler chickens. Escherichia coli (E. coli), Salmonella and Clostridia perfringens (C.perfringens) were isolated and identified from diseased broiler chickens. Laying chickens were immunized with E. coli O78, S. enteritidis and C.perfringens type C. IgY antibodies were extracted from egg yolk by ammonium sulfate precipitation method. The molecular weight of the produced IgY antibody was confirmed by SDS-PAGE. Titers of antibodies in serum of immunized chicken and egg yolk were determined by ELISA. The efficacy of oral passive immunization with specific IgY against the previous pathogens was evaluated in broilers. 1 day old chicks were divided into 10 groups, each containing 20 birds, group 1 (negative control), group 2, 3, 4 (preventive, control positive and treatment group, respectively) of E. coli, group 5, 6, 7 (preventive, control positive and treatment group, respectively) for Salmonella, and 8, 9, 10 (preventive, control positive and treatment group, respectively) for Clostridia. Blood samples were collected from birds of all groups to measure the antibody titer in serum. Clinical parameters (signs, mortalities and post-mortem examination), performance parameters (body weight and feed intake and feed conversion rate (FCR)), and re-isolation rate were evaluated. Histopathological examination of organs from all groups was recorded. In conclusion; ELISA test, pathogenicity test, performance parameters, re-isolation rates, pathology and histopahological results revealed that oral administration of purified specific IgY protected broiler chickens from homologous challenge, and able to reduce the effect of microorganism after treatment with IgY when compare with challenged group.