Day-old vaccination of maternally immune turkeys against Newcastle disease.

Maternally immune day-old turkey poults were vaccinated against Newcastle Disease with La Sota live vaccine and, concurrently, with emulsion killed vaccine. After an initial fall in maternal antibody the haemagglutination inhibition (HAI) geometric mean titre (GMT) of these birds rose to log2(6) and persisted at that level for eight months. Re-vaccination of some birds at 10 weeks with the emulsion vaccine caused GMTs to rise to log2(11). Six months later these levels were at log2(7). Further emulsion vaccination at 28 weeks produced a good anamnestic effect, the titre rising to log2(12). The authors discuss the possible advantages of this programme of vaccination as a routine for the immunisation of both fattening and breeding birds.