Risk factors associated with leg disorders of gestating sows in different group-housing systems: a cross-sectional study in 108 farrow-to-finish farms in France.

Group-housing, rather than individual-housing systems, is mandatory for gestating sows in the European Union (2008/120/EEC). However, leg problems occur more frequently in group-housing than in individual-housing systems and are a welfare and health concern. A cross-sectional study involving 108 farms in western France was carried out to see whether the type of the 4 main group-housing systems (i.e. large groups with electronic feeder station in stable or in dynamic groups, small groups in walk-in lock-in stalls or partial feeding stalls), and other husbandry practices, were associated with leg disorders. In each farm, the sows were examined visually for claw lesions, scored for lameness and their breeding characteristics were recorded. Lameness was positively correlated with heel lesions and dewclaw lesions. A concrete slatted floor, as compared to straw, was a major risk factor (unadjusted relative risk (RR)=9.9; 95% confidence interval (95% CI): 4.4-34.5). Walk-in lock-in stalls were found to be the most protective system. A logistic regression model was used to identify those factors which significantly increased the risk of leg problems. These factors were: housing in large groups (RR=1.5; 95% CI: 1.1-2.4), dirty floors (RR=1.6; 95% CI: 1.0-2.9), high level of ammonia (RR=1.5; 95% CI: 1.1-2.1), severely restricted feeding particularly during the last stage of pregnancy (RR=1.5; 95% CI: 1.0-2.1) and a high number of sows per stockman (RR=1.5; 95% CI: 1.0-2.4).