To produce PRRSV MDA positive piglets, six pregnantseronegative sows (coming from a PRRSV naïve farm)were vaccinated with a PRRSV-1 based attenuated vaccine(Suvaxyn PRRS MLV) at maximum release dose(105.2 TCID50/dose) during the first half of gestation(45 days of pregnancy). The day before the expected farrowingdate, parturition was induced with an intramuscularinjection of cloprostenol (Cyclix® Porcino, Virbac).All sows farrowed the next day.