Effect Of PRRSV Serum Domestication On Production Performance Of Sows In Large-scale Pig Farms

Throughout the global pig breeding industry,there are numerous animal diseases that can have a huge economic impact on it.However,there are very few viral infectious diseases that can affect the world,the time span can span half a century,and can change the color of many farming companies.But PRRS is one of them.It is a pity that due to many factors such as the rapid mutation rate of the porcine reproductive and respiratory syndrome virus(PRRSV)genome,the diversity of strains,and the low homology between different strains,there is no particularly effective solution to control PRRS.Therefore,this paper conducts PRRSV genomic characteristics analysis,serum acclimation,and systematically evaluates the effect of serum acclimation on the performance of gilts in large-scale pig farms.1.Analysis of PRRSV genomic characteristics of large-scale PRRS outbreak farms.In a pig farm in Shandong Province,a serious infectious disease broke out in the first half of 2016.We finally determined that it was PRRS through laboratory testing.Further analysis of the characteristics of the viral genome revealed that the PRRSV strain RD-YL belongs to the evolutionary branch of the NADC30-strain and is in the cluster of NADC30-like strains.The nucleotide homology with NADC30,JXA1,VR2332,CH1 a and other representative strains were 94.2%,84.2%,85.3% and 84.7%,respectively.It shows that it shares the highest nucleotide homology with the NADC30 strain.The recombination analysis using Simplot software revealed that the gene sequence of JXA1-like strain was recombined between 7321 nt and 8039 nt of RD-YL NSP2 coding region.We judge that it is a recombinant strain formed by the NADC30-like strain,which belongs to the predominant strain cluster among PRRSV epidemic strains in recent years,and has low homology with other vaccine strains.So,it is difficult for currently commercial PRRSV vaccines to prevent and control it effectively.2.Establishment of PRRSV serum acclimation program for gilts and evaluation of its effect.Serum acclimation is a newly PRRSV prevention and control scheme.Studies have reported that it can increase PRRSV antibody in pig populations and maintain it at a high level.The factors that determine the effect of serum domestication mainly include the type of PRRSV strain selected for domestication,the original serum dilution ratio during the domestication of the serum,and the immune status of the domesticated sow herd.In this study,domesticated sows were newly introduced healthy reserve pigs without PRRSV interference.The above RD-YL strain was used as a domesticated PRRSV strain because it belongs to an epidemic strain and it is a strain that has ever erupted in this farm and has regional characteristics.The dilution ratio of domesticated serum is obtained through serial dilution,and it has been verified by animal experiments.According to the above scheme,the domestication of serum in healthy reserve pig herds has successfully enabled herds to produce high-efficiency antibodies in a short period of time.And the average monthly abortions,sow deaths,litter average stillbirths,and litter average mummies were all significantly reduced;sow inventory,delivery rate,litter average weaned piglets,weaned piglets,PSY and others have increased to varying degrees.In summary,this study used the positive sera of the predominantly popular PRRSV strain RD-YL isolated in this field to sero domesticate healthy gilts,which significantly improved the performance of gilts.This study proves that serum domestication can be used as an effective method to prevent and control PRRS in large-scale pig farms,and provides theoretical basis and technical support for large-scale farms to effectively prevent and control PRRS through serum domestication.