Effect of challenge with t-strain infectious bronchitis virus on early lay pullets after different vaccination histories

The effect of T-strain infectious bronchitis virus on early lay pullets that had received different first vaccinations, and their third vaccination at either 14 or 18 weeks, was examined. For the whole flock there was an immediate decline in egg internal quality after challenge with the virus. Shell quality also declined as evidenced by both objective measurement and visual assessment. There were no major effects due to the strain of vaccine that the birds received at day old, although there were some effects of vaccine protocol. The revaccination of birds at 5% lay (18 weeks old) resulted in an increased decline in egg quality measurements when they were challenged with T-strain. This flock is continuing to be monitored to assess long-term effects.