| Since the porcine circovirus type 2(PCV2)infection appeared in China in 2000,the disease has caused huge economic losses to the pig industry.Pigs infected with PCV2 alone did not show serious clinical symptoms,but the immune system was severely damaged,leading to mixed infection or secondary infection of various disease.Vaccine immunization is considered to be an effective methods to prevent this disease.However,there are many kinds of PCV2 vaccines and their effects are uneven.Therefore,it is of great significance to systematically evaluate the effect of PCV2 vaccines and to guide the selection of appropriate vaccines for breeding farms.This will further improve the production efficiency of pig farms.In this study,21-day-old piglets of the same batch and similar weight were selected from two scale pig farms to compare the clinical effects of three vaccines.Vaccines of porcine reproductive and respiratory syndrome(PRRS)and classical swine fever(CSF)were immunized before the experiment.The farm 1 is one-sites feeding pattern.920 piglets are weaned and continue to be raised in this farm.However,after weaning,480 piglets of farm 2 were transferred to the breeding households for further feeding.Firstly,pigs from farm 1 and farm 2 were randomly divided into four groups(A,B,C and D)according to their body weight,respectively.There was no significant difference of the body weight between each group by one-way ANOVA.The pigs of group A were immunized with the Ingelvac CircoFLEX subunit vaccine(vaccine 1)of Boehringer-Ingelheim Company;the pigs of group B were immunized with a domestic inactivated vaccine(vaccine 2);the pigs of group C were immunized with another domestic inactivated vaccine(vaccine 3);and group D was the control.All the pigs were labeled after immunization.All pigs were mixed according to the principle of "double blindness on both sides" to ensure that there were no differences in the feeding environment between different groups.The average daily gain was no significant difference between the four groups in both two farms at 21 days after immunization.The average daily gain of pigs in group A and B was significantly higher than that of control group in farm 1(p<0.05),especially that of group A was significantly higher than that of other vaccination groups.The average daily gain was no significant difference between four groups in farm 2 at 158 days after immunization.In addition,the final body weight was 141.11kg in farm 2,which was higher than that of farm 1(131.24kg).The rate of death and elimination in farm 2 was lower than that of farm 1.Before immunization with PCV2,the infection rate of PCV2 in farm 1 was 44.4%,the infection rate of PCV2 in farm 2 was 25%.The positive rate of PCV2 antibody was 100%in two farms.PRRSV and swine influenza virus(SIV)were negative.These results showed that both farms were not infected with PRRSV and SIV;but infected with PCV2 before immunization.After 21 days of immunization,the positive rate of PCV2 antibody was still 100%,but the infection rate of PCV2 changed to 0 in both two farms.After 88 days of immunization,the positive rate of PCV2 was still 0 in farm 2,but the positive rate of PCV2 was 40%in farm 1.There were no severe infectious diseases such as CSF,PRRS and PR in the two farms.These results indicated that pigs were infected with PCV2 in farm 1,and PCV2 infection seriously affected the growth performance and the rate of death and elimination.In conclusion,immunized with PCV2 vaccines had no significant effect on the growth performance of pigs with low PCV2 infection rate(farm 2).However,immunized with PCV2 vaccines had significantly improved the growth performance of pigs with high PCV2 infection rate(farm 1).Especially,the group A immunized with vaccine 1 had the most significant effect on the growth performance.Compared with the single-site feeding pattern,the two-sites feeding pattern can effectively block the spread of PCV2 and other pathogens,reduce rate of death and elimination,and improve the growth performance.Therefore,when the infection rate of PCV2 is high,it is recommended to immunize with PCV2 subunit vaccine,which can significantly improve the average daily gain and improve the production efficiency of pig farms. |
