Noninfectious factors associated with pneumonia and pleuritis in slaughtered pigs from 143 farrow-to-finish pig farms

Abstract

A cross-sectional study involving 143 farrow-to-finish herds was carried out to identify herd-level noninfectious factors associated with pneumonia and pleuritis in slaughter pigs. Data related to herd characteristics, biosecurity, management and housing conditions were collected by questionnaire during a farm visit. Climatic conditions were measured over 20h in the post-weaning and finishing rooms where the slaughter pigs were kept. After these on-farm investigations, the finishing pigs were examined at slaughter for lung lesions. A sample of 30 randomly selected pigs per herd was scored for pneumonia and pleuritis. Herds were grouped into three categories according to their pneumonia median score (class 1: ≤0.5; class 2: 0.5<score≤3.75; class 3: >3.75). For pleuritis, a herd was deemed affected if at least one pig had a high pleuritis score (≥3). A multinomial logistic regression model was used to identify factors associated with pneumonia classes 2 and 3. A logistic regression for binary outcome was used to identify risk factors for severe pleuritis. An interval of less than four weeks between successive batches (OR=4.5, 95% confidence interval (95% CI): 1.5–13.6, p<0.01), large finishing room size (OR=4.3, 95% CI: 1.6–11.6, p<0.01) and high mean CO2 concentration in the finishing room (OR=4.2, 95%CI: 1.6–11.3, p<0.01), significantly increased the odds for a herd to be in class 2 for pneumonia. The same risk factors were found for class 3 and, in addition, a direct fresh air inlet from outside or from the corridor in the post-weaning room vs an appropriate ceiling above the pigs (OR=5.1, 95% CI: 1.4–18.8, p=0.01). The risk for a herd to have at least one pig with a high pleuritis score was increased when the farrowing facilities were not disinsected (OR=2.7, 95% CI: 1.2–5.8, p=0.01), when tail docking was performed later than 1.5 days after birth (OR=2.6, 95% CI: 1.2–5.7, p=0.01) and if the piglets were castrated when more than 14 days old (OR=2.7, 95%CI: 1.1–6.8, p=0.03). A temperature range of less than 5°C for the ventilation control rate in the farrowing room (OR=2.7, 95% CI: 1.2–5.9, p=0.01), a mean temperature in the finishing room below 23°C (OR=3.0, 95% CI: 1.3–6.8, p<0.01) and large herd size (OR=3.1, 95% CI: 1.4–6.9, p<0.01) were also associated with increased risk of pleuritis. The factors affecting pneumonia and pleuritis seemed to be different. All rearing steps from farrowing to finishing must be taken into account in any health programme aimed at controlling pneumonia and pleuritis and lung health may be improved through several pathways, i.e. correcting managerial and hygienic factors, implementing an appropriate and well-functioning ventilation in order to offer favorable climatic conditions.