Pathogenicity Of NDV To Chickens Of Different Age And Different Level Of Antibody

The chickens were immunized by vaccine on 7days and 20 days. We examined the antibody level of the 10-day,20-day and 30-day chickens'by HI experiment, we divided the broilers with different antibody into two groups(H and L group) according antibody data. The pathogenic model were built by infecting 10-day,20-day and 30-day chickens with NDV. Every five chickens were randomly selected by HI experiment on the 3rd,6th,9th and 12th day after the infected experiment. Through dynamic observing on symptom,pathological changes and laws of antibody level of infected chickens, and the weight of the body ,the mean weight of immune organs were measured. And real time RT-PCR was used in the experiment.The result showed that chickens of different days and different antibody level were diagnosed as atypical Newcastle Disease, and the primary pathological change was the necrosis of all lymphoid tissue. The state of the disease of the L-group was more serious than the H-group and 10-day chickens are more serious than 20-day and 30-day chickens. Hemorrhage of the trachea and cencal tonsils of L groups was more serious than H groups'. The pathological change was changed with the days.The Antibody level of different days of the infected chickens showed the identical regulation, the Antibody level rapidly declined and then gradually ascended, the Antibody level of the H group was always higher than the L group's. The weight of the 26- day H group was significantly higher than the L group'. The spleen and the bursa to body weight ratio of the 29-day H group were significantly higher than the L groups'. The weight and the mean weight of the immune organs of 33-day H group were higher than the L groups', but...