A field study on the evaluation of safety and effectiveness of the attenuated Infectious Bursal disease vaccine when applied to day-old chicks at the hatchery

The study was conducted to evaluate the safety and effectiveness of a new attenuated Gumboro vaccine, MB-1 in Luong Phuong chickens. A total of 27,700 one-day-old Luong Phuong chicks were vaccinated with the MB-1 vaccine at a dose of 0.1 mL/bird at the hatchery. The results showed that the level of IBD maternal antibodies on the day of vaccination reaching an average titer of 4,857. The MB-1 vaccine virus was in the Bursa of Fabricius from 24 to 36 days old. The Bursa Lesion Score (BLS) was moderate; gradually increased from 0.67 to 3 points and decreased with signs of recovery to 2.33 points at 36 days of age. The Bursa Index at 21 days of age was 0.39% and decreased to 0.1% at 36 days of age. The humoral immune response to ND vaccination was high, reaching an average titer of 4,448 at 42 days of age. Especially, MB-1 induced a strong immune reaction leading to high IBD antibody titers and more uniformity, reaching an average titer of 3,632 with a low CV of 22%. In summary, the application of MB-1 vaccine at the hatchery would provide one-day-old chicks with early localization of the vaccine virus in the Bursa and rapid and uniform development of active IBD antibodies. The MB-1 vaccine did not affect the immune response of chicks to the ND vaccination and was safe for the Bursa when applied to commercial day-old broiler chicks at the hatchery.