The Monitoring Research Of Antibodies Produced In Sows Immunized With PED Vaccine

Since 2010,the outbreak of porcine epidemic diarrhea(PED)in China,with a high incidence and mortality of piglets,caused great losses in the pig industry.One of the reasons for the prevalence of this disease is poor immune responses.It is urgent to determine the best immunization program to prevent PED.In this study,we conducted a test to detect antibodies in different immunization programs.The levels of Ig G and Ig A against PED in serum and colostrum of sows,and in serum of their piglets were detected.The influences on the Ig A level of breast milk of sows by different PED vaccines,immunization schedules and immunization dosages were studied.The results are as follows:1.In the serum of sows,the Ig G level of PED was not positively correlated with the Ig A level of PED.2.There were obvious differences between the levels of IgA in porcine serum of sows taken from different pig farms and immunized the same way,but there was no obvious difference between the levels of Ig A in porcine colostrum.Whereas the Ig A levels of sow serum from the same pig farm and immunized in different ways,were almost the same,but there was an obvious difference between the level of Ig A in porcine colostrum.In short,the levels of Ig A in porcine colostrum were more sensitive and can be used as criteria for the detection of immune status in PED.3.Both the live vaccine and the inactivated vaccine of PED could induce colostrum Ig A antibodies;however,the immune antibody level induced by the live vaccine was higher than that induced by the inactivated vaccine with the same inoculating times.For example,the average value of colostrum Ig A OD in the groups inoculated twice with the live vaccine was 1.330,whereas it was 0.754 in the inactivated vaccine group.4.The difference among values of colostrum IgA OD with different immunization schemes was as follows: immunized twice with the live vaccine two doses>immunized once with the live vaccine for 5 doses >immunized twice with the live vaccine and once with the inactivated vaccine >immunized twice with the live vaccine for 1 dose>immunized once with the live vaccine and once with the inactivated vaccine>immunized once with the live vaccine for one dose.This result provides a reasonable way to immunize pigs against PED:immunized once with the live vaccine for 5 doses could be used as emergency vaccination for increasing antibody level quickly;immunized twice with the live vaccine two doses could be used inducing high level of antibody for the pig farms under high PED stress;immunized twice with the live vaccine and once with the inactivated vaccine could be used as routine immunization.5.The same immunizing schemes were applied in different pig farms,and there was a difference between OD values of Ig A in porcine colostrum.6.Immunized with the same PED vaccine and the same schemes,the average OD value of Ig A in colostrum of first farrowing sows was 1.157,whereas in colostrum of multiparous sows was up to 1.535.7.There was no significant difference between products from different companies if immunized with the same procedure.For example,the OD value of Ig A in porcine colostrum was 1.567 immunized with the A company's live vaccine and the inactivated mixed vaccine group,whereas that was 1.537 immunized with the B company's triplex live vaccine and inactivated vaccine group and that of the C company's triplex live vaccine and inactivated mixed vaccine group was 1.539.In summary,the evaluation criterion of vaccination against PED was determined,and the immune effects in sow with different immunization procedures and different types of vaccines were compared,and a reasonable immunization program was proposed,which would have important implication for the prevention and monitoring of PED.