Antibodies specific to infectious bronchitis in broilers in Ceará state, Brazil

The experiment was carried out to determine the antibody levels to infectious bronchitis virus (IBV) in 1120 broilers of two broiler flocks, both from the same parental flock and free from previous vaccination. Forty chicks of each line were alloted to the control group and the sera were tested by indirect ELISA. The vaccination program consisted on the administration of commercial vaccines against IBV at 10 and 25 days of age. Chicks with low levels of maternal antibodies (Mab) did not show significant titers to the first vaccinal stimulus. They presented a vaccinal response to the second vaccinal stimulus reaching the top around GMT 1100 at 45 days. Chicks with high Mab titers did not show significant titers to the primary and secondary vaccinal stimuli, reaching peak levels of GMT 500 at 45 days. No antibody response was detected after the primary vaccination at day 10. A delayed antibody response was detected after the secondary vaccination on day 25, indicating no previous priming. The maternal antibody titers can interfere on the response to the first and second vaccinal stimulus promoting the neutralization of the first vaccination and a different response to the second one, according to high or low maternal antibodies.