Evaluation Study On The Immune Effieacyof Three Type Porcine Circovirus Vaccines

Porcine circovirus widespread epidemic,to the world's pig industry has brought serious economic losses,but also the current pig industry affect the growth performance of piglets an important reason.Vaccine immunization is an effective measure to prevent and control ring disease.Recent studies have shown that subunit vaccines based on circular virus recombinant proteins and whole virus inactivated vaccines can provide effective protection against circovirus infection.The aim of this study is to investigate the circovirus infection in Luzhou area,compare the effect of whole virus inactivated vaccine and genetically engineered vaccines on the pig's immune effect and pig performance,and select the best cost for the large-scale pig farms in Luzhou Ring vaccine lay the foundation,the following results:1.Epidemiological survey of porcine circovirus in large-scale pig farm in Luzhou.In this study,we collected serum samples from pigs including replacement gilt,pre-pregnancy,post-pregnancy,lactating,120-day,and 180-day from six large-scale pig farms.Moreover,we also collected the serum from those pigs without receiving immunization of the swine fever virus and receiving second immunization of the swine fever virus.The total number of serum is 480.Epidemiological investigation by detecting the existence of pathogens in serum using commercial PCV-2 indirect ELISA kit or PCR assay demonstrated.Epidemiological survey of pathogens showed that the average positive rate of pathogen was45%,and the positive rate in those farms unvaccinated circovirus vaccines was higher than that of farms vaccinated circovirus vaccines by more than 20%.From the aspects of growth,the pigs at lactation stages share the highest positive rates up to 43%.For the piglets at120-day,the positive rates reach to 70%.The overall positive rate was 89%.The positive rate among glits was 100%,and the positive rates among multiparous sow at all stages were higher than 85%.With growth,the positive rate among the piglets decreased and then increased;the total positive rates in piglets at 180-day were 100%.Collectively,the PCV-2 infection in large-scale farms in Luzhou is serious.2.Benefit analysis of circovirus vaccineAt present,the major types of circovirus vaccines in market are imported genetic vaccine(V1),domestic genetically engineered vaccine(V2),and domestic virus inactivated vaccine(V3).In this study,400 piglets born on the same day and sharing close weigh from pig farms with severe infection or no infection were selected.Piglets were randomly divided into 4groups: one control and three experimental groups with 100 piglets in each group.Piglets in the experimental group were injected intramuscularly V1,V2,or V3 vaccine when they were21 day old;the control piglets were treated with identical volumes of normal saline(V4).Side effects after receiving vaccine,serological changes,daily gain in body,and input-output ration were recorded and analyzed.The results showed that no side effects after immunization were observed;the positive rate of serum antibodies reached to 100% in piglets aged 180 days.The daily gain of V1 group was significantly higher than that of the other groups(20-30 g/d)(P <0.05),and the ratio of input to output of V1 group was the highest.3.Effects of circovirus vaccine on production performance of swine.In the current study,120 replacement gilts and 120 sows at third pregnancies were chosen.Three experimental groups with 30 sows in each group were injected intramuscularly V1,V2,or V3 vaccine;the control sows were treated with identical volumes of normal saline.We recorded the average number of piglets born and healthy piglets.Moreover,the birth weight for each piglet was also recorded.For replacement gilts,there was no significant difference in the total number of piglets born among these four groups(P > 0.05).The number of healthy piglets in the V1 vaccine group was significantly higher than that in other experimental and the control groups(P < 0.05).No significant difference in birth weight among four groups was observed(P > 0.05).Interestingly,replacement rate of sows at second pregnancies in control group was significantly higher than experimental groups.For multiparous sows,there was also no significant difference in the total number of piglets born among these four groups(P > 0.05).The number of healthy piglets in the experimental groups was significantly higher the control(P < 0.05),reaching to one piglets.Likely,the number of invalid piglets in control group was significantly higher the experimental groups,reaching to one piglets.For birth weight of piglets,no significant difference was observed(P > 0.05).Collectively,V1 vaccine can effectively increase the litter size and thus increase the economic efficiency of large-scale pig farms.