Willingness to walk for a feed reward in lame and non-lame sows

Lameness causes welfare and production related problems. Research is needed to detect mild cases of lameness and its impact on welfare and production. Lameness could also influence the willingness to walk for feed rewards. Motivation tests are used to measure animals’ willingness to work for a reward, e.g. feed. The objective of this study was to investigate the impact of lameness on the ability to cover distances for feed rewards. Ten non-lame and 10 mildly to moderately lame hybrid sows were selected by using gait score. All sows were fed daily with 2.6 kg of a commercial gestation diet. After habituation to the experimental area, sows had to walk around a Y-shaped barrier, placed between two feeders, to receive a new reward. Sows were trained daily for 10 minutes. Training was considered successful when sows received at least 4 feed rewards during a session of 10 minutes. Feed rewards (apples and raisins) were presented after using both light and sound as a signal of an available reward. Sows were tested 3 times individually, once per day on 3 non-consecutive days. The effect of lameness on willingness to work for a feed reward was investigated using a Poisson model with gestation stage, parity range and body weight as fixed effects. The willingness to walk for feed rewards did not differ significantly between lame and non-lame sows (P=0.164). These results suggest that either the locomotary ability is not strongly reduced in sows with a low to moderate degree of lameness, or that the present motivation test is not sufficiently sensitive to detect these sows. Sensitivity of the test could possibly be improved by reducing the attractiveness of the feed rewards or increasing the work load during the test.