Enzootic pneumonia: comparison of cough and lung lesions as predictors of weight gain in swine

Estimates of the association between enzootic pneumonia (EP) and weight gain were obtained from multiple linear regression models using coughing episodes or slaughter checks as indicators of EP status in a prospective cohort study in a commercial pig herd. Models were estimated for pigs in 2 different age groups: roasters (n = 1084, sold at 32 to 50 kg) and market hogs (n = 1162, sold at 100 to 110 kg). Clinical evaluations were performed weekly, and coughing episodes recorded for each pig. Lungs were inspected at slaughter, and scores were expressed as the percentage of the lung with gross pneumonic lesions. Coughing and lung scores were significantly correlated, after adjusting for other covariates (R = 0.32 and 0.59, respectively, for market hogs and roasters). However, the agreement beyond chance between coughing history and lung lesions at slaughter was poor among both roasters and market hogs (kappa = 0.17 and 0.07, respectively). Weekly assessment of coughing was not a sensitive indicator of lung lesions at slaughter. In multiple regression, lung score was a highly significant predictor of lower final weight in both age groups. A significant decrease in final weight was also evident in pigs with onset of coughing occurring more than 30 days before slaughter (for roasters) or more than 60 days before last weight measurement (for market hogs).