[Vaccination of sows against Mycoplasma hyopneumoniae with Hyoresp].

The aim of the study was to investigate the serological reactions of pregnant sows to vaccination with Hyoresp. Further investigations were performed in the offspring of these sows to follow the dynamics of maternal antibodies and the reaction to vaccination at different points in time. The study was conducted in three farrow-to-finish herds endemically infected with M. hyopneumoniae. A total of 30 gilts and 31 sows were vaccinated 8 and 4 weeks ante partum with Hyoresp (Merial GmbH) or given phys. saline solution as a placebo. The offspring was divided into three groups receiving Hyoresp at 1 and 4 or at 4 and 8 weeks of age. The control group was treated with phys. saline solution at 1 and 4 weeks of age. Before vaccination, antibodies against M. hyopneumoniae were detected in 85% of the gilts and 68% of the sows, confirming the endemic infection of the herds. Vaccination of the sows induced a significant increase in the antibody concentration in serum within four weeks and enhanced the concentration of antibodies in the colostrum. As expected, significantly enhanced levels of antibodies were also detected during the first four weeks of life of the offspring of vaccinated sows. The piglets' serological reaction to vaccination at 1 and 4 weeks of age showed marked interferences with maternal antibodies, so that a reaction could be demonstrated only at 8 weeks of age. The serological reaction of piglets vaccinated at 4 and 8 weeks of age was much stronger than that of piglets vaccinated earlier. Surprisingly, the vaccination status of the sow had no effect on the serological response of the piglets in either vaccination scheme. Maternal antibodies are known to reduce the risk of M. hyopneumoniae infections in piglets. Vaccinating the sows against M. hyopneumoniae may thus be an option for farrowing-to-finish herds with an enhanced risk for infections due to ineffective separation of different age groups, poor gilt acclimatisation or high gilt replacement rates.