Osteochondrosis in pigs
Abstract: Osteochondrosis (OC) is a growth cartilage disease initiated by ischemia which causes a focal delay in the endochondral ossification. It is a common joint disorder in fattening pigs causing lameness and joint condemnation at slaughter. Another cause of lameness and joint condemnation in fatteners is Erysipelothrix rhusiopathiae arthritis (ERA). Pigs in organic production more often have joints condemned at slaughter than do pigs in conventional production. Outdoor access is mandatory in organic production, and the aim of this thesis was to examine whether a housing type that is common in organic production affects the prevalence of OC, ERA and joint condemnation at slaughter in fatteners. Fatteners were also scored for their gait to evaluate any association between lameness and OC, ERA and joint condemnation. Post-mortem examination of joints showed that 95% of examined fatteners had OC. Pigs that could range freely indoors and had access to pasture and an outdoor paddock had more prevalent and more severe OC than did pigs confined to conventional small indoor pens. One explanation may be that free-range pigs are more active and receive more load on their joints, which may promote OC development. Pigs with many and severe OC lesions had their gait affected more than did pigs with less OC. Free-range pigs did, however, not show more lameness than confined housed pigs. Exercise strengthens muscles, tendons and bone tissue, which may render the free-range pigs less clinically affected by OC. A 100% seroprevalence of Erysipelothrix rhusiopathiae was detected in both free-range and confined pigs, but no joints with ERA were diagnosed. The association between lameness and joint condemnations was poor, and the joint condemnation rate appears to be a bad assessment of joint health. Computed tomography scans of hock joints in wild boars indicate that OC is rare in wild boars. As wild boars roam and are hunted, selection pressure may have favoured those with healthy joints that are well adapted to an active life. More research on wild boars and hybrids between domestic pigs and wild boars may help understand which features in domestic pigs need alteration to secure enhancement of their joint health. In summary, changes in housing systems and a pig breed with more robust joints may be needed for a sustainable organic pork production.
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