Preventing lameness in group housed sows

Lameness is a fundamental problem on sow farms. In group housing systems sows are even more dependent on healthy claws than in individual housing systems. Lameness is both a threat for animal welfare as for production. A review on sow claw health in the last 20 years learns how to prevent lameness in group housed sows. Although lameness can be scored relatively easy, the incidence and repeatability is lower than of claw lesions. An inspection of 15.000 claws showed that hind claws had three times more lesions that front claws and that the outer digits had six times more lesions than the inner digits. Scoring the hind outer digits turned out to be the most efficient way to assess sow claws. The most important floor characteristics effecting claw health are abrasiveness, friction, softness, slot/slat size ratio, and moisture. Aggressive interactions also play an important role in the aetiology of lameness. Abrasiveness of good quality concrete floor gives symmetric wear of the hooves resulting in the right gait. Plastic and smooth metal floors are not suitable for sows. A lack of friction like on dirty floors leads to slippery floors with risks on claw and leg injuries. Especially in a situation with aggressive interactions a high level of friction is important. Softness is important to prevent erosion of the heel and cracks in sole and side wall. Slatted floors should be designed on claw dimensions with slots narrow enough to prevent injuries but wide enough to prevent dirty and slippery floors. Openings of 18-22 mm and slats of 80-90 mm seem to be the optimum. Claws become fragile in moisty conditions with manure and urine. A dry floor is necessary for good claw health. In a social environment with aggressive interactions the risk on claw lesions and lameness is high and highly correlated with skin lesions. Minimizing mixing moments is a key factor for good claw health in group housing. The decrease of lameness in Dutch group housing systems in the last 20 years learned that claw health can be positively affected by housing and management.