Abstract:

Effect of four commonly used immunization program of Newcastle disease in commercial broiler were detected under the high maternal antibody titer, the results indicated that the level of maternal antibody had decreased significantly, the change was not significant in group but significant between groups. After the second inoculation, maternal antibody still had great interference with the live vaccine group, the antibody titer below the protection level(6 log2) at 55 days old, but the antibody titer of the 7-day-old group higher than 3-day-old group. Maternal antibody had small interference with the group used both inactivated vaccine and live vaccine, antibody level of 3-day-old group up to 6log2 at 50 days old while antibody level of 7-day-old group up to 6.4log2 at 45 days old and rose to 7log2 at 50 days old and maintained to the end of trial. The antibody level of 7-day-old group which was about five days ahead of schedule to achieve the level of antibody protection was higher than the 3-day-old group.

Key words: Newcastle disease; maternal antibody; broiler; immunization program