The impact of endemic porcine reproductive and respiratory syndrome virus and other pathogens on reproductive performance in swine

Objectives: To evaluate the impact of endemic infection with porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), transmissible gastroenteritis virus-porcine respiratory coronavirus (TGEV-PRCV), pseudorabies virus (PRV), Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae (APP) on the reproductive performance of sows. Methods: Seventeen groups of 30 to 60 sows and gilts in seven herds were monitored over a 2-year period by serological testing for the pathogens listed above. Litter size, number of stillborn (including mummies), average weaning weight, preweaning deaths, and interfarrowing interval were recorded for the sows that were tested. Multiple linear regression analyses were performed to evaluate the association of the measures of reproductive performance with serological test results. Results: Infection with PRRSV was consistently associated with poorer reproductive performance. Sows that had antibodies to PRRSV had, on average, 0.1 to 0.9 more stillborn piglets per litter than did seronegative animals. The average interfarrowing interval was 3 to 10 days longer for PRRSV-seropositive sows. A consistent correlation between reproductive performance and serological results could not be found for SIV, TGEV-PRCV, PRV, M hyopneu-moniae, or APP. Implications: Even in herds where no clinical signs of the disease are present, reproductive performance may be substantially inferior in sows with high levels of antibody against PRRSV.