The Influence Of PRRSV On Growth Performance And Immune-Related Indexes

Porcine reproductive and respiratory syndrome caused by porcine reproductive and respiratory syndrome virus is a highly contagious pig disease. The mainly symptoms for the pregnant sow are reproductive disorders such as early abortion, stillbirth, mummified and weak fetus. For the other ages of pigs, occurrence of respiratory symptoms always be performed. Finally, piglets with the disease subject to high mortality.Susceptivity to PRRSV was showed among different varieties as well as different ages of pigs. In clinical practice, we found PRRSV resistance of different kinds of pigs is differentiated, but what kinds of pigs are resistance or susceptible to PRRSV has not been proved by experiment. Extensive researchs showed PRRSV could inhibit to the immune system of host, then due to more susceptible to other pathogens. Thus, how to enhance the autoimmunity in the prevention and control for PRRS is the key point. In the present market, many types of immunopotentiators have been appeared, but the effectiveness of the medicine remains to be assessed. Therefore, we have acted the reaserches on resistance and regulation of the PRRS in different breeds of the pig and immunopotentiators, respectively.1. Pathogenic research of highly pathogenic porcine reproductive and respiratory syndrome for different kinds of pigs28 day-old PRRSV-negative piglets in 6 breeds (Landrace, Large White, Duroc pigs, pig through town, Qingping pig, Meishan) were used. Piglets infected with Porcine Reproductive-Respiratory Syndrome (PRRSV) base deletion strains WUHAN-1 in muscles. The influence of virulent PRRSV in growth performance and immunity-related indicators were researched by daily monitoring of temperature and feed intake, regularly physiological and biochemical testing of anticoagulant and serum samples, analyzing of immune-related cytokines, observations of clinical and pathology symptoms and RT-PCR detection of material.The results showed that the highly pathogenic PRRSV can damage the body humoral immunity, cellular immunity and cytokine immune response, leading to immune system disorders, decreased immunity and eventually died; Qingping breeds have the strongest resistance to the PRRSV among the 6 breeds, subsequently are Tongcheng and Meishan pigs. Resistance of three kinds of foreign species lower than domestic, the subsequence of susceptivity to PRRSV is Landrace, Large White and Duroc. Meanwhile, highly pathogenic PRRSV due to immunosuppression which due to more susceptible to other pathogens. The majority of infected Tongcheng pigs that infected Hemophilus parasuis speeded up the death.2. Immunity influence of PRRSV attenuated strain to piglets and accommodation of immunopotentiators28 days old PRRSV-negative piglets were immunized intramuscularly with PRRSV attenuated vaccine, immunopotentiators were added in feed or not. The influence of attenuated strain PRRSV in growth performance and immunity-related indicators were researched by detecting the average daily gain and average weight gain, collecting periodic serum samples and testing of anticoagulant Physiological and biochemical and analyzing to immune-related cytokines. The immunopotentiators influence to post-vaccination piglets in growth performance and immunity-related indicators were also reseached.The results showed that PRRSV attenuated strain can stimulate the body to produce specific immune responses, so that the body in a state of immune protection to enhance the body's resistance PRRSV; two immunostimulants could significantly improve the performance of weaned piglets (average weight gain), And show the promoting effect on immune protection associated with the indicators (blue ear antibody levels, IFN-y, IgM, IgG concentration, white blood cell count, globulin),but show no affection on some conventional physiological and biochemical indicators(red blood cell, platelet, hemoglobin, white protein, total protein), Suggesting that the two immunopotentiators are safe and harmless immune-enhancing biological agents.Through this experimental study, preliminary pigs from six breeds were screened two more resistant varieties of the PRRSV pigs (Qingping and Duroc pigs), as the basis for subsequent research; on the other hand, the two immunostimulants PRRS vaccine can enhance the effect of raising swine herd immunity, which provides help to the integrated control of PRRS and production practice.