Seroprevalence of antibodies against Lawsonia intracellularis among growing pigs raised in indoor versus outdoor units

OBJECTIVE: To determine change over time in sero-prevalence of antibodies against Lawsonia intracellularis among growing-finishing pigs housed in indoor versus outdoor facilities. DESIGN: Serologic survey. ANIMALS: 93 pigs born to seropositive gilts and raised in indoor (n = 49) or outdoor (44) growing-finishing facilities. PROCEDURE: Blood samples were collected from the pigs 2, 6, 10, 14, 18, 22, and 26 weeks after birth and tested for antibodies against L intracellularis with an indirect immunofluorescence assay. RESULTS: None of the pigs were seropositive 2 or 6 weeks after birth.Ten weeks after birth, 74% and 76% of pigs in indoor and outdoor growing-finishing facilities were seropositive, respectively, whereas 14 weeks after birth, the percentage of pigs in indoor growing-finishing facilities that were seropositive was substantially higher than the percentage of pigs in outdoor facilities that were. From 18 weeks after birth to the end of the study, none of the pigs in outdoor growing-finishing facilities were seropositive, whereas low percentages of pigs in indoor facilities were seropositive 18, 22, and 26 weeks after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that seroprevalence of antibodies against L intracellularis decreases faster among growing-finishing pigs housed in outdoor facilities than among growing-finishing pigs housed in indoor facilities.