To satisfy stringent welfare criteria a farrowing pen must meet the sows’ needs for freedom of movement and allow her to exhibit most normal behaviours.

Pens must be designed which provide adequate space for the loose housed farrowing sow but which have additional features to promote high standards of pig care. The sow should not be left to farrow indiscriminately within the pen but must be provided with an enriched environment to satisfy both her needs and those of the piglets. Within the pen the sow requires a suitable nest site and material to manipulate immediately pre-farrowing. These features can only be provided when it becomes known what the sows’ find desirable. In previous work it was shown that sows’ preferred to build their nests and farrow within a cubicle rather than in a corner or against a straight but open wall and that sows exhibit intensive nest building activity in the 14 hours before farrowing. In this trial the objective was to determine the farrowing sows’ response to an arrangement of parallel walls spaced 0.55, 0.95 and 1.35 m apart. The rationale behind the measurements was that they approximated to the body width, height and length of a generalised sow. Information about the sows’ response to such a wall arrangement would be useful if pens with walk-through nests were being designed.