Protection of broilers against Newcastle disease by hyperimmunisation of the dams.

A flock of broiler parents was hyperimmunised against Newcastle disease (ND) by subcutaneous injection of an experimental high-potency inactivated oil emulsion (IOE) vaccine in order to achieve high and long-lasting passive protection in broilers. During the egg production period mean log2 HI ND titre of the parents slowly decreased from 11.6 at 26 weeks of age to 10.0 at 53 weeks of age. Titres of day-old progeny paralleled those of their parents. Mean protection of broilers against mortality following challenge with Herts 33 virus at the ages of 1, 2, 3 and 4 weeks was 86%, 73%, 54% and 44%, respectively. As compared with the current Dutch situation, application of the high-potency IOE vaccine will significantly increase antibody titres in parent flocks and the level and duration of passive protection in broilers. It is concluded that passive ND protection of broilers by hyperimmunisation of the dams is realisable from an economic point of view and is suitable for low-risk areas.