Abstract

A potency trial was conducted to evaluate the potency of four commonly used infectious bursal disease (IBD) live vaccines to determine the most appropriate vaccination response to establish the most appropriate vaccination programme against IBD in Nigeria. A total of 700 day old cockerels were randomly divided into six groups 1, 2, 3, 4, 5, and 6. Groups 1 to 4 were the vaccination cockerels while Groups 5 and 6 were the positive and negative controls. The chicks were sub divided into five groups A, B, C, D and E representing the different schedules that is, 1 and 3 weeks, 2 and 4 weeks, 3 and 5, 1, 3 and 5, 2, 4 and 6 weeks, respectively. After each vaccination, the chicks were observed for clinical signs of IBD. Two weeks after each vaccination, chicks were challenged with IBD virus, onset of clinical signs, morbidity and mortality rates were observed. Sample of bursa was collected from 5 birds at 3 and 7 days post challenge from dead as well as necropsied birds. The lesions were scored on the scale of 0 to 5 (mild to severe). Vaccine 3 appeared to be the best with the mean of 1.8 for gross lesions, 1.2 for histo-pathological lesions, 0.6 for clinical signs, 0.6 for mortality, 0.2 for antibody titre and 1.8 for bursal body weight ratio. Schedule A (vaccination at 1 and 3 weeks) also was the best for all the vaccines. Therefore, Nigerian poultry farmers are advised base on the aforementioned result to use vaccine 3 and schedule A in the control the outbreaks of IBD.

Key words: Cockerels chicks, live Infectious bursal disease (IBD) vaccines, potency, vaccination schedule, vaccination strategies.