^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 subcutaneously in the neck.

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

^d White Pekin breeder ducks normally start egg production at 24 weeks old. 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 progeny.