Objective: In order to determine the decreasing maternal antibody and increasing the active antibodies against IBOV in pullet flocks.
Design: Field trial.
Animals: Fourty comercial pullet flocks, each flocks with more than 10,000 birds from one day to 13 weeks old.
Procedure: Five different vaccination programs (treatment) with two different live and one killed IBD vaccines, were used. Each vaccination group included 10 flocks (replicate) with at least 10000 birds. The birds of group "A" received the live vaccine of
IBD type "a" (078 strain) in drinking water at days 10, 16 and 21
of age. At day 10 of age they were also vaccinated by killed IBD vaccine subcutaneusly. The birds of group "B" received the live vaccine of IBD type "b" (Bur- 706 strain), while the vaccination program was similar with group A. Vaccination program of group C, was similar with group A and program of group D was similar with group B, except they were not used killed IBD vaccine at 10 day old. Vaccination program of group E was
similar with group D and the only difference was that type "b" of live IBD vaccine was also sprayed droplet at one day old. In each replicate 25 blood samples were taken from pullets, weekly from I to 13 weeks old. All the blood samples were tested with KPL ELIAS kits for determining the antibody titer against IBDV.
Statistical analysis: One way ANOV A was performed and when a significant overall effect (P Results: There is no difference in decreasing maternal antibody between five vaccination methods. When the maternal antibody decreasing to very low level, the vaccine could stimulate the immune system and the active titer was appeared. In those flocks that both killed and live IBD vaccines were used were increase active antibody titer were increased about one week sooner than the others at 5 weeks of age.
Conclusion: The present study shows that the optimal age for the first IBD live vaccination could be when the maternal drive
antibody is 1000 and/or less than 1000 in birds. This means the beneficial time could be 14±3 days of age. J. Fac. Vet. Med Univ. Tehran. 57, 4: 43-48, 2002.