Visit order in an automated feed distributor in groups of pregnant sows : impact of access hour and social rank

The objectives of this study were to verify the impact of a modification to the access hour 1) on visit order to the Automated Concentrate Dispenser (ACD) and 2) on the stability of the hierarchy of pregnant sows, 3) and also to examine the possibility of using visit order to measure hierarchy. Four groups of 13 gestating sows in an ACD‐equipped pen had their access hour modified.The dyadic test was used to measure the social rank of the sows: it was repeated before and after modification to the access hour.The correlations between visit order to the ACD before and after modification to the access hour and between social ranks measured at the same periods were strong and positive (rs=0.74 and rs =0.89 respectively, P < 0.0001). The visit order to the ACD and the social rank were not correlated before modification to the access hour but were positively correlated after (rs=0.39 (P = 0.06) and rs=0.60 (P = 0.01) respectively). Modification to the access hour to the ACD seemed to have no impact on the visit order.Stability of the social hierarchy did not seem to be affected by a change in the access hour to the ACD. Visit order does not appear to be a reliable way of measuring social hierarchy.