Abstract: To observe and compare application effects on egg breeders inoculated with infectious bronchitis LDT3-A freeze-dried vaccine,a China's own developed vaccine strain. Test group immunization with LDT3-A strain freeze-dried vaccine and control group immunization with Ma5+clone30 strain bivalent freeze-dried vaccine in first immunization;after the first immunization,flocks immunization other infectious bronchitis live virus vaccine and inactivated vaccine(e.g. H120,H52) according to the immunization program,and vaccination was identical between the two groups. The results showed that more slightly stress response in three-day age egg breeders intranasal vaccinated with LDT3-A strain freeze-dried vaccine at 1.2 times amount;after subsequent supplementary immunization,the test groups had been effectively protected,while the control group occurred infectious bronchitis in flocks. Compared with control group,total mortality reduced 10.11%,151 to 210 days age average egg production rate increased by 7.0%,the eggs pass rate,fertilization rate,hatching rate and healthy chicks rate increased by 3.0%,2.3%,0.7% and 3.2%,respectively,and feed-egg ratio decreased 0.1 in test group. These results provided clinical evidence for selecting infectious bronchitis vaccine and optimal immunization programs in egg breeder farms.

Key words: LDT3-A strain; infectious bronchitis; freeze-dried vaccine; egg breeders; immunogenic effect