Relationships among seroconversion to Mycoplasma hyopneumoniae, lung lesions, and production parameters in pigs

Maria Sitjar, DVM; Elizabeth P. Noyes, DVM, PhD; Xavier Simon, DVM; Carlos Pijoan, DVM, PhD

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Objective-- To assess the value of observing lung lesions at slaughter as a measure of lifetime pneumonia, to investigate the role of Mycoplasma hyopneumoniae in lifetime pneumonia, and to investigate the relationship between lifetime pneumonia and growth performance.

Materials and methods-- Forty-eight pigs from a 150-sow farrow-to-?nish 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 weeks until slaughter. Lung parenchymal densities were determined from the radiographs and an average lifetime pneumonia (ALP) score was calculated. For each pig, radiographs were evaluated over time and used to determine when the pneumonia involved the highest percentage of the lung (pneumonic peak). Lungs were collected at slaughter and super?cial lung lesions were measured. At the same time, pneumonic tissue was dissected and its relative volume was determined for each lung. For each weekly group of pigs, average daily gain (ADG) was calculated and correlated with pneumonic lesion measures (average lifetime pneumonia, volumetric pneumonia, and super?cial pneumonia) for each pig as well as for each group. Onset of seroconversion to M. hyopneumoniae and A. pleuropneumoniae was tested for correlation with onset, extent, and severity of radiographic pneumonic lesions (ALP) and lung lesions seen at slaughter.

Results-- A significant correlation between peak average pneumonia and seroconversion to M. hyopneumoniae was found. Groups showing early onset of infection had higher ALP and higher pneumonia peaks. Lesions seen at slaughter were a poor indicator of both average lifetime pneumonia and peak pneumonia.

Implications-- M. hyopneumoniae appears to play an important role in the pneumonic peak of pigs. The growth of pigs infected later in the finishing phase with M. hyopneumoniae is less compromised than that of pigs infected earlier in the finishing phase.

Keywords: pneumonia, Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, radiography

RIS citationCite as: Sitjar M, Noyes EP, Simon X, et al. Relationships among seroconversion to Mycoplasma hyopneumoniae, lung lesions, and production parameters in pigs. J Swine Health Prod 1996;4(6):273-277.

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