Rising and Falling Rule of Serum Antibodies in Pigs vaccinated with Swine Streptococcosis Inactivated Bi-combined Vaccine

The serum antibody titer were examed with AGP and ELISA methods in pigs vaccinated with the inactivated bi_combined vaccine of swine Streptococcosis.The results showed that antibodies appeared 4 days after vaccination,turn_positivation rate of antibodies was 100% after 7 days,anibody titer reached summit during 15 to 30 days.Second vaccination was done at 35th day.Antibody titer began to rise obviously after 5 days of second vaccination,the titer was still maintained at 1∶1 600 after 6 months vaccination.Maternal antibody titer of sucking pigs produced by sow vaccinated two times was higher and lasting.The test also showed that the pigs could resist 1×10 7 CFU Streptococcus equi subsp zooe pidemicus  and 1×10 8CFU Suis type 2 attack respectively when antibody titer was not less than 1∶800.