Materials and methods—Forty-eight pigs from a 150-sow farrow-tofinish farm with a history of respiratory problems were weighed and bled every 2 weeks until slaughter. Serum samples were processed for serology to measure antibodies against M. hyopneumoniae, Actinobacillus pleuropneumoniae, and pseudorabies virus (Aujeszky’s disease). In addition, the thorax of each pig was radiographed every 2 w...
