Prevalence and risk factors of claw lesions and lameness in pregnant sows in two types of group housing

Claw lesions and lameness in sows are an important welfare concern as well as a cause of considerable economic loss. These problems are more common in group housing than in individual housing systems. Given that group housing for gestating sows will become mandatory in the EU from 2013 onwards, the aim of the present study was: (1) to determine the prevalence of lameness and claw lesions in sows housed in groups during gestation, and (2) to analyze whether the type of group housing system and sow-related factors were associated with lameness and claw lesions. Eight Belgian pig herds with group housing of gestating sows were selected. Four herds used pens with electronic sow feeders (dynamic groups), the other four herds kept their sows in free access stalls (static groups). All sows were visually examined for lameness at the end of gestation. Claw lesions were scored after parturition. Information about feed, housing conditions and culling (strategy) was collected, as well as information about parity and breed. Of all 421 assessed sows, on average 9.7% (min. 2.4%, max. 23.1%) were lame. Almost 99% of the sows had one or more claw lesion with overgrowth of heel horn (93%) and cracks in the wall (52%) as the most prevalent lesions. Neither for lameness nor claw lesions was significant differences found between the two types of group housing. Lameness decreased while the mean claw lesion score increased with ageing. These results suggest that lameness can be caused by reasons other than claw lesions, especially in older sows. Although no difference was found between the two types of group housing, a huge variation between herds was observed. Moreover, as the prevalence of lameness and claw lesions in group housing is quite high and group housing will become mandatory in 2013, further investigation on risk factors of locomotor disorders in sows is necessary.