RESUMEN
The effect of tuftsin of embryo and post-hatch vaccination with NDV-F was studied. The embryo vaccination with NDV-F resulted in more number of dead-in-shell embryos. To overcome this problem, the vaccine was treated separately with ethyl methane sulfate (EMS) and 5-fluorouracil (5-FU) and administered. Treating the vaccine with 5-FU resulted in better hatchability as compared to EMS treatment. In embryo, NDV antibody titres increased upto 2 weeks of age and declined thereafter, whereas in post-hatch vaccination, the antibody titre increased from second to fourth week of age and declined thereafter. The seroconversion was better when the vaccine was given along with tuftsin either to embryos or chicks (post-hatch vaccination) as compared to those vaccinated without tuftsin. Moreover, the percentage of hatchability was more in tuftsin administered groups. It was found that embryo vaccination can ensure definite protection during the early life of the chicks despite the presence of maternal antibodies. In cases where breeder vaccinations do not result in concomitant transfer of antibody to progeny chicks, embryo vaccination would give only neonatal resistance. During the later stages, embryo vaccination did not confer any advantage over post-hatch vaccination.