effect of mixed live vaccines of newcastle disease and infectious bronchitis on systemic and local antibody responses in chickens

In the present study, 360 male day-old broiler chicks were used to determine the effect of mixed live vaccines of Newcastle disease [ND] and infectious bronchitis [IB] on serum and local antibody responses to IB. Chicks were randomly divided into 12 treatment groups of 3 replicates and reared for 40 days on floor pens. Groups 1 to 5 received mixed ND and IB vaccine. Groups 7 to 11 received IB vaccine alone and regarded as positive controls. Group 6, that received ND vaccine only, and group 12, that received no vaccine, were considered as negative controls. Antibody titer against IB in the nasal washings and sera was measured using enzyme-linked immunosorbent assay [ELISA]. The chickens were inoculated with IB live vaccine [strain HI 20] with or without ND live vaccine by means of an eye dropper. Serum samples obtained on the 19th and 29th day of age and serum samples, as well as nasal washings, collected on day 40, were used to determine systemic and local antibody responses to IB. On the 40th day of age, tracheal samples were also collected to study the probable pathologic lesions due to the effect of live vaccines used. There was no significant difference in systemic antibody response [SAR] among all groups measured on the 19th day. On the 29th and 40th day of age, SAR of the negative control groups was significantly [P<0.05] different from those received IB vaccine. On the 40th day, nasal washings showed higher antibody titer as compared to the systemic antibody titer [P