Regular revaccination for infectious bronchitis virus in laying hens: advantages and disadvantages

Different vaccination protocols for infectious bronchitis virus (IBV) were administered to ISA Brown laying hens during rearing and half the birds were revaccinated regularly during lay. At 57 wks of age, half of the birds were placed into an induced moult (moulted prior to revaccination), all birds were then revaccinated for IB and the other half of the birds moulted (moulted following revaccination). Production and egg quality were lower in the birds that were revaccinated regularly during lay, especially from 18 to 56 weeks. IB antibody titres increased at 6 and 16 weeks, then decreased and remained relatively constant from 27 to 77 weeks, increasing markedly following exposure to T-strain IBV. Egg shell quality was better in the birds that were revaccinated prior to moult. There appears to be little advantage, and some disadvantage, of regular revaccination during lay, provided that the birds have been effectively vaccinated during rearing.