^a A live, avirulent vaccine consisting of the three major serotypes (1, 2, and 5) of R anatipestifer

^b A formalin-inactivated cell suspension of the three major serotypes (1, 2, and 5) of R anatipestifer. Bacterins and killed virus vaccines are administered SC in the neck.

^c A modified-live virus vaccine of chick embryo origin.

^d White Pekin breeder ducks normally start egg production at 24 wk of age. Egg production can be accelerated or delayed and breeder vaccination should be completed before the onset of egg production to optimize the passage of parental immunity to the progeny.