Effects of confinement on social interaction patterns in dry sows

Abstract

The aim of the present study was to investigate how the social interaction patterns and the aggression regulation within dry (non-lactating) sow groups were affected by confinement. Studies were carried out in three different herds, representing three different housing systems. In the first system (de-confinement), the animals were housed in groups of 5, with individual feeding stalls, a common dunging area and a common lying box (net floor area, 3.04 m 2/sow), in the second (semi-confinement), they were housed in groups of four, with individual combined feeding and lying stalls, and a common dunging area (net floor area, 2.27 m 2/sow), and in the third (confinement), they were confined in individual stalls (floor area 1.40 m 2/sow). Four groups were studied in de-confinement, three in semi-confinement and three in confinement. Confinement decreased the social activity, measured as number of observed interactions per time unit, and led to unsettled dominance relationships combined with high aggression levels. The semi-confinement system did not provide sufficient space for a stable social system. The frequencies of aggressive behaviours were highest in semi-confinement, but since some relationships could be settled, and a certain amount of submissive behaviour was noted, the aggression level was probably lower than in confinement. The de-confinement system provided enough area for the sows to settle dominance relationships and to keep the aggression level fairly low.