|Background: Free-range housing, in which pigs have access to both indoor and outdoor areas, is mandatory in
organic pig production in Europe, but little is known about the effects of this housing on joint health in pigs. A
high level of joint condemnations at slaughter has been reported in organic free-range pigs in Sweden, compared
with pigs raised in conventional confined housing. We hypothesised that biomechanical forces imposed on the
joints of pigs that range freely promote the development of osteochondrosis and lead to joint condemnation.
We compared the prevalence of osteochondrosis and other joint lesions (e.g. arthritis, traumatic) in the elbow
and hock joints of 91 crossbred Hampshire (Yorkshire × Landrace) fattening pigs that were housed in a free-range
indoor/outdoor system with that in 45 pigs housed in confined indoor pens.
Results: A larger proportion of free-range than confined pigs had osteochondrosis in the elbow joints (69 vs. 50%,
p < 0.05), and a higher proportion of these joints in free-range pigs showed moderate or severe lesions (33 vs. 16%,
p < 0.05). The free-range pigs also showed a higher prevalence of osteochondrosis in the hock joints (83 vs. 62%,
p < 0.05) and a larger proportion of these joints had moderate or severe lesions (69 vs. 33%, p < 0.001). At slaughter,
4.2% of the free-range pigs had condemned joints, all of which showed severe osteochondrosis, while no joints of
confined pigs were condemned.
Conclusions: In this experiment the prevalence of osteochondrosis in the elbow and the hock was higher, and
lesions were more severe, in free-range than in confined pigs, suggesting that free-range housing increases the risk
of acquiring osteochondrosis. Increased biomechanical stress to vulnerable joint structures may be the mechanism
behind this effect, however more studies are needed to verify these results. This study suggests that modification
of housing, and breeding for joints that are more adapted to free-range movement may be needed in free-range
pig production. Severe osteochondrosis is a cause of joint condemnation, but the condemnation rate at slaughter
underestimates the actual frequency of joint lesions and hence is a poor assessment of joint health.
Keywords: Pigs, Housing, Organic, Free-range, Joints, Osteochondrosis, Elbow, Hock