| Summary: | 碩士 === 國立嘉義大學 === 獸醫學系研究所 === 104 === Infectious bursal disease (IBD) is a disease of major economic importance in the poultry industry in Taiwan, because it not only causes chicken clinical symptoms but also develops immune suppression for young chickens. Live vaccines were commonly used in Taiwan, but they can affect the efficacy of maternally derived antibodies or damage the bursa of Fabricius directly. A licensed vector vaccine of infectious bursal disease imported to Taiwan recently and in this study, we evaluated the efficacy of the vector vaccine for the production performance and the protection of bursa in the field. From May 2013 to July 2015, we collected chickens in Yunlin, Changhua, Chiayi, Tainan and Pingtung from 5 native chicken farms and 2 broiler farms. The experimental groups used IBD vector vaccine and the control groups used live IBD vaccines and the other raising conditions were the same. Physical and serological samples were collected in 0, 1, 2, 3, 4,and 5 weeks from broilers, and the samples from native chickens were collected in 0, 1, 2, 3, 4, 5, 8-9, and 11-12 weeks. For production performance, we randomly weighted 50 cocks and 50 hens for average weekly weight gains and recorded the survival rates in the end of the feeding cycles. We collected serum samples from each farm and checked the IBD antibodies titers by a commercial kit. The bursa and body weight ratio was checked. Histopathological exams were done for the lesion scores depending on the depleting of lymphocytes in bursa.
Our study showed that no matter in broilers or in native chickens, the production performance of vector vaccine groups was better than that of live vaccines groups.
In the age of 3-5 weeks, the antibody titers of IBD in the vector vaccine groups were better than that of the live vaccine groups with significant differences. It showed that the vector vaccine groups has shorter immunity gap than that of the live vaccine groups and has lower risk to outbreak IBD. The bursa atrophy were significantly in the live vaccine groups at 4 weeks old. The depletion of lymphocytes was seriously in the live vaccine groups from 4 to 5 weeks old with significant difference. The result of the current studies showed the protection of the vector vaccine was better than that of live vaccines.
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