Peak of lay infection with infectious bronchitis virus: its impact on egg quality parameters of four strains of laying hen

The eggshell quality of vaccinated hens challenged with infectious bronchitis (IB) virus in-lay at 41 weeks of age was found to decline. These effects were observed in hens vaccinated only during the growth phase and not revaccinated during the lay period. T strain virus was found to have a more prolonged impact while the antigenically-different Nl/88 strain produced a greater decrease in egg quality parameters. There was an unexpected increase in internal quality of the virus-exposed groups during the challenge period. While the genetic strain of the hen had no significant effects on the response to challenge in terms of egg quality, there were inherent strain differences in egg quality unrelated to the challenge and these are briefly discussed.