The Prevention And Treatment Effect Of Glycerol Monolaurate On Porcine Reproductive And Respiratory Syndrome

Porcine reproductive and respiratory syndrome(PRRS)is an infectious disease caused by porcine reproductive and respiratory syndrome virus(PRRSV).The main clinical manifestations of PRRS are severe reproductive disorders of sows and respiratory diseases of pigs in various stages.Some highly pathogenic wild virus infections can cause a large number of deaths in pigs.It has been more than 30 years since the discovery of PRRS in the United States in 1987.PRRS has been spread all over the world,and it will bring huge economic losses to the global pig industry every year.Since PRRSV entered China in 1995,it had experienced several rounds of outbreaks,which seriously restricted the healthy development of pig industry in China.The research on PRRSV vaccine prevention and drug treatment has never stopped.Domestic pig production has the characteristics of high breeding density,relatively complex breeding environment and high pressure of disease prevention and control.Because PRRSV is prone to mutation,the effect of vaccine immune cross protection between different strains is uncertain.The pig farms seriously affected by PRRS usually need to add drugs to stabilize production.In clinical application,most of the traditional antibiotics have little significance in the prevention and control of PRRSV.These drugs are more used for some secondary or concurrent infections of bacterial diseases.Therefore,the screening of drugs that can inhibit PRRSV has always been a hot work of researcher.In recent years,more and more natural substances or Chinese herbal extracts have been chosen by researcher to resist PRRSV.GML has also been used in PRRS prevention and control,but its mechanism and effect on PRRSV are not clear.In order to explore the inhibitory effect of GML on PRRSV in vitro,glycerin laurate powder and a kind of black water fly insect oil containing 35% glycerin laurate were respectively mixed with PRRSV for incubation,and then infected normal growing cells.The results of cytopathy observation,virus titer and nucleic acid content showed that the cytopathy of PRRSV was significantly improved after the mixture of glyceryl laurate powder and gadfly oil.The virus titer was significantly reduced(P < 0.05),and the nucleic acid content was also reduced in varying degrees,which confirmed the inhibitory effect of GML on PRRSV in vitro.On this basis,a group of 140 day old pigs with PRRS antigen and antibody double negative were selected in this study,10 pigs in each group were pre-fed with GML drugs,and three other drug groups commonly used for PRRS clinical prevention were set as the control groups,then the pigs were attack with TP strain with strong virulence.After the attack,it was found that the GML group showed a certain advantage over the blank control group and other drug groups in terms of average daily weight gain,mortality and disability rate.Only one pig died in the GML group,two pigs were damaged,and the casualty rate was 30%,while more than five pigs died in the other drug groups and the blank group,and the casualty rate was over 60%.It can be concluded that GML can inhibit PRRSV infection and virus replication in pigs to a certain extent,and has a good protective effect.In order to further explore the effect of GML on improving the performance of PRRS positive sows in clinical application,two batches of four production lines of sows were tested successively in this study.The first and third lines were the test group,the second and fourth lines were the control group,and the number of sows in the four production lines were 141,145,148 and 161 respectively.First line,second line,third line and fourth line are the same period of pig production.After feeding GML to the first-line and third-line sows from 90 days of pregnancy to weaning,it was found that the average number of healthy piglets in the first-line and the second-line control group was 11.2 and only 10.8 in the same period;the rate of ineffective piglets in the first-line and the second-line control group was 13.04% and 16.80%,respectively,which was significantly improved compared with the control group.On the other hand,the average number of healthy fetuses in the same period was 11.69 in the third line group,and only 10.73 in the fourth line control group.In addition,the two groups of sows in the delivery room survival rate,weaning rate and other performance indicators showed better improvement than the control group.In this study,the invitro inhibition test of PRRSV,the invivo protection test of GML and the improvement test of production performance of sows were carried out to determine the effect of GML on PRRSV.This study provides some reference for the application of GML drugs in PRRS disease prevention and control.