Keeping sows in large groups necessitates ‘dynamic’ grouping, that is, the removal and addition of sows at regular intervals to a group of more or less constant size. However, the lack of stability of dynamic groups raises questions about the nature of the dominance hierarchy and the pattern of feeder use within them. Behaviour and feeder use was observed in a dynamic group of 35-40 sows by both direct observation and video-recording over 13 feed cycles. An initial 4-day recording was made of a stable group of 40 sows to evaluate each sow's feeder use before removal/addition began. On three occasions at weekly intervals five sows were removed and five trained sows added to the group after feeding. Recording covered each day before addition, the day of addition and the following day. Direct observation was carried out for 8 hours on the days before each addition and for 6.5 hours on the following days, starting within 20 minutes of sows being added to the group. The 25 sows remaining in the group throughout removal/addition (‘resident’ sows) were individually marked and observed. Each batch of five sows added was marked as a group and each groups’ feeder use and social activity was recorded.