Vaccination of day-old broilers against infectious bronchitis: effect of vaccine strain and route of administration.

Nine groups of 10 one-day-old broiler chicks were vaccinated by eye-drop, coarse spray, or intratracheal instillation with combined Newcastle disease-infectious bronchitis live vaccines containing the Massachusetts (Mass) 41, Holland 120, or Connecticut 46 strain of infectious bronchitis virus (IBV). Chickens vaccinated with Mass-41 or Holland 120 were protected against challenge with a Mass strain administered at 4 weeks of age. When immunity to the disease was evaluated by virus recovery, detection of IBV by fluorescent antibody, evaluation of ciliary activity, histopathology, and virus-neutralization titers, the group vaccinated with Connecticut 46 did not show protection. Vaccination at 1 day of age resulted in an antibody response and increased resistance to challenge with Mass-41, regardless of vaccination route.