Relationship of growth performance to pneumonia and atrophic rhinitis detected in pigs at slaughter

Abstract

Summary Three commercial swine herds were selected for study, because pigs at slaughter consistently had lung lesions typical of bronchopneumonia and snout lesions consistent with atrophic rhinitis. Pigs were reared in the conventional system for each herd except that they were identified at birth and weighed at various intervals. At slaughter, individual pig lungs and snout were examined for lesions of pneumonia and atrophic rhinitis, respectively. Lesions were scored and correlated with growth indicators for each pig. Included in the growth indicators were: average daily gain (growing phase), average daily gain (finishing phase), average daily gain (total), and days to reach 104.5-kg body weight. Additionally, for each pig, scores for lung lesions were correlated to grades for snout lesions. Three correlation coefficients for measurements of pigs within herd B were significant and included days to 104.5-kg body weight and grades for snout lesions, ‒0.15 (P < 0.02); average daily gain (finishing) and grades for snout lesions, 0.17 (P < 0.01); and average daily gain (total) and grades for snout lesions, 0.16 (P < 0.01). Contrary to findings in other investigations, pigs that attained market weight at the youngest age did not have the lowest score for lung lesions, the lowest grade for snout lesions, or the least extensive or severe lesions. Combining data from all 3 herds, the mean scores for lung lesions and mean grades for snout lesions decreased significantly (P < 0.05) as the age of pigs at slaughter increased. All other statistical correlations were not significant. Results do not justify the use of scores for lung or snout lesions evaluated at slaughter to estimate the reduction in growth rate or the economic impact of pneumonia or atrophic rhinitis.