Abstract: To study the protective efficacy and the optimal immunization procedure of Newcastle disease, infectious bronchitis and avian influenza (H9 subtype) vaccine, inactivated Strain La Sota +Strain M41 +Strain SS/94 in the broiler of yellow feather chickens, the triple vaccine immunized yellow feather chickens by different immunization procedure. Results showed that the vaccinated chickens have the similar antibody variation to ND, IB and H9. The antibody titers were low when the triple inactivated vaccine were injected only once at 10 day-old. After the secondary and third immunization at the 20 or 40 day-old, or 10-day-old first with Newcastle disease virus (La Sota strain) and avian influenza virus (H9 subtype, SS/94 strain) vaccine, inactivated for primary immunization and then strengthened the immune with the triple inactivated vaccine at the 20 or 40 day-old, the antibody titers quickly ascended and maintained a long time. According to the results, proposed that on the basis of the normal immunization procedure, it may inject the triple inactivated vaccine at 20 day-old with 0.3 mL per chicken for short feeding period chickens and at 40 day-old with 0.5 mL per chicken for long feeding period chickens.

Key words: ND; IB; AI-H9; triple inactivated vaccine; immunization program