Study of an immunization plan for broilers via the spray method against Newcastle disease using vaccines from the Bl and La Sota strains

Studied was the immunization pattern against Newcastle disease in birds with the use of a spray method on broilers obtained congenitally from their mothers, having antihemagglutinins. All birds on one of the premises ( a total of 14, 000) were vaccinated when 5 days old with a liquid vaccine of strain B1 (one fourth dose per bird) using the Dutch pulverizing apparatus Flox-10 -- group I. Other 14,000 birds of another of the premises of the same batch were treated at the same age with the same dose via the same route of application of a liquid vaccine of the La Sota strain --group II. All birds of the two groups were revaccinated in the same way at the age of 25 days with a vaccine of the La Sota strain at the rate of a whole dose per bird. The birds were kept under equal conditons of feeding and management. It was found that they built immunity which protected them fully from Newcastle disease up to the end of the fattening period (2 months). This was demonstrated by the test for establishing resistance to a control infection with a highly virulent strain of the Newcastle disease virus (challenge) as well as serologically by the hemagglutination inhibition reaction. At the slaughter by the end of the fattening period all period all birds of the two groups sshowed almost equal average body weight, however, those of group I manifested 0.97 per cent lower mortality rate and lower forage intake per kg weight (by 23 g on an average).