A total of ninety broilers chicks were reared for a defined period of time until they reached to two months of age after completion of vaccination program required for broiler chickens. The chicks were divided into three groups (A, B and C) of 30 chicks each, and housed separately into chicken pens divided into three compartments, they were fed daily and given water ad-libitum. Two vaccines against IBD were obtained from two different companies (CEVAC and LAPROVET) to be used for vaccination of the chicks. Chicks in group A were vaccinated using CEVAC vaccines, CevacR Gumbo L (Winterfield 2512 G-61 strain) on day 7 of age, and Cevac IBD L on day 14. Chicks in group B were vaccinated on day 7 and 14 of age, with Avi IBD Inter from LAPROVET. Chicks in group C served as non-vaccinated controls. Both vaccines were administered in drinking water, making sure that the water was free of any trace of disinfectants. Vaccine virus was protected from chlorine in drinking water by adding skim milk (0.5L/20L) to the water. The chicks were deprived of water two hours before vaccination. One dose (bottle of 500 doses) of each type of vaccine used was mixed in 5 litres of water according to the manufacturer of the vaccines used. On days 7, 14, 21, and 28 after vaccination, the chicks were bled and sera were harvested from clotted blood samples and stored at -20oC. Indirect Enzyme-Linked Immunosorbent Assay (ELISA) was used to measure IBDV antibody titers and compare between and within the two groups. Antibody titers were high for the first-week post-vaccination for chicks vaccinated against IBD in both groups (A and B). Every chick in the two groups had a protective antibody titer with the average titer for group A being 5544.595 and group B being 5693.594. According to the kit manufacturer, the minimum protective antibody titer is 875. It was concluded that the two vaccines elicited protective immune response against IBD in broiler chickens with the latter being more protective.
Keywords: Infectious bursal disease, Antibody titer