Association between Enzootic Pneumonia-like Lung Lesions and Carcass Quality and Meat pH Value in Slaughter Pigs

Abstract

Although the prevalence of respiratory diseases in slaughter pigs ranges from 19% to 74% and continues to be an important concern for swine herds worldwide, only a few studies have investigated the relationship between respiratory disease and pork quality. The general aim of this study was to investigate associations between the prevalence and severity of enzootic pneumonia-like lesions in Polish slaughter pigs on different carcass and meat-quality characteristics at the animal and herd levels. The average prevalence of bronchopneumonic lungs with different degrees of lesions was 94.57%. The majority of lesions indicated the acute stage of enzootic pneumonia. Our results indicate a statistically significant interaction between the mean weight of carcasses depending on the extent of the lesions (p = 0.04) at the animal level. The correlation between meatiness and severity of lung lesions was r = -0.25 (p = 0.00). The correlation between the extent of lung lesions and pH₄₅ value was r = -0.17 (p = 0.005) on the animal level and r = -0.63 (p = 0.017) at the herd level. This implies that lung lesions in slaughter pigs negatively influence not only animal health and welfare, but also carcass quality.

Keywords: PRDC; bronchopneumoniae; pork quality; swine.

Figure 1

Description of the selection of the analyzed sample, depicting included and excluded subjects.

Figure 2

The enzootic pneumonia-like lesion scoring system according to Christensen methodology [37] used in the study. The percentage of each lobe considers—the volume it occupies in relation to the whole lungs. LL: left lung lobe, RL: right lung lobe, A: apical lobe, C: cardiac lobe, D: diaphragmatic lobe, *: cranial part of diaphragmatic lobe.

Figure 3

The schema of grouping on animal and batch level based on prevalence and severity of EP-like lung lesions. The grouping criterion was absence/presence of lesions (expressing prevalence of lesions at two levels). Subgrouping criterion was severity of lesions, expressed by lung scoring result at animal level and expressed by percentage of affected surface in bronchopneumonic lungs at batch level. – group of animals without EP-like lesions; + group of animals with mild EP-like lesions; ++ group of animals with moderate EP-like lesions; +++ group of animals with severe EP-like lesions. * Scoring units: points according to Madeck and Kobish grid, maximum total score, 28 points. ** Scoring units: percentage, according to CLP software, maximum total score, 100%.

Figure 4

Histopathological findings in lung tissue samples. (A–C) Gross cranioventral pulmonary consolidation associated with enzootic pneumonia. There are distinct peribronchiolar inflammatory cell cuffs composed of macrophages, lymphocytes, plasma cells, and eosinophils (asterisks). The bronchial mucosa is thickened and infiltrated with variable numbers of inflammatory cells (arrows) (A,B). (D) Healthy lung tissue. No microscopic changes are observed. HE. Scale: 20 μm (A); 50 μm (B); 200 μm (C); 500 μm (D).

Figure 5

Percentage of carcass classes in 1.740 carcasses. The bar chart shows the percentage of the individual carcass classes on the EUROP scale in batches with different extensions of lung lesions. −: batches with no evidence of EP-like lung lesions; +: batches with mild EP-like lesions; ++: moderate EP-like lesions; +++: severe EP-like lesions. S, E, U: classification notes in EUROP scale.