Dominance allows animals priority of access to resources when these are limited. It is common practice to feed dry sows once or twice daily a relatively small amount of food. This can lead to high competition for food, when there are no provisions for individual feeding of group housed sows. In contrast, competition for food should be low when offered ad libitum. This study was designed to investigate the effect of feeding regime on the measurement of hierarchies in group housed dry sows.

Four groups of 12 multiparous sows were housed in deep straw pens (3.1 m2/sow). Two groups were offered a high fibre diet ad libitum from a three-space hopper (LC) and two groups were floor-fed 3 kg/sow of a standard diet once daily (HC). The diet composition is given in Brouns et al (1992).

Groups were allocated to treatment after service. After two months on treatment, the dominance of every sow in each pen was determined in a feed competition test between all possible dyads of sows. A more detailed description of this test is given in Brouns et al (1992). The results of this test indicated how many pen mates each sow dominated (DR). This was used to calculate an index of linearity for the hierarchy (Appleby, 1983) giving a value between 0 and 1, where 1 indicates a completely linear hierarchy.