Breeding hens of similar age, 9 to 11 months old, were selected from four flocks, each with a different vaccination history. One flock received no vaccinations, the second received spray and wing web Newcastle disease (ND) vaccine, the third was given three ND dust vaccinations, and the fourth received two dead ND viral vaccinations.https://digitalcommons.library.umaine.edu/aes_techbulletin/1191/thumbnail.jp
