Sow preferences for farrowing under a cover with and without access to straw

In semi-natural environments sows often select a protected nest site at farrowing. Investigations of nest site selection under indoor conditions are scarce but suggest that sows prefer to nest and farrow under a covered area. Since feed-back from a functional nest may improve maternal behaviour and thus piglet survival we investigated if access to a covered area and ad libitum access to straw would improve maternal behaviour of importance for piglet survival. We used forty-four primiparous sows housed in large individual pens from approximately 2 weeks prior to expected parturition. The sows were randomly distributed to four treatment groups of +/− ad libitum access to straw combined with +/− access to a covered area in the pen. The sows' position in the pen (left or right side) was observed from 24h prior to birth of the first piglet until 24h after using 10-min interval scan sampling and the temporal pattern of sow position in relation to position of the cover (left or right side of the pen) was studied. Furthermore, postural and nest-building behaviours were observed, as well as situations where the piglets were either at risk of being crushed or were crushed. The results showed no significant influence of cover on sow position. Odds-ratio for choosing the covered farrowing position was 1.4 (95% creditability interval (0.4-5.1)). The temporal pattern of sow position showed that the probability of observing the sows in the part of the pen classified as the farrowing position increased from close to 0.5 to 1 as parturition approached and stayed high during the 24h observation period after birth of the first piglet, except for a small drop around 12h after birth of the first piglet. However, the tendency to stay in the nest during farrowing was not increased neither by cover nor by ad libitum access to straw. Access to cover significantly increased prepartum nest-building behaviour (F ₁,₂₉ =4.27, P =0.05) whereas there was no significant influence of access to straw. However, it should be taken into account that all sows had access to sawdust on the floor, which may also serve as a nesting material. The number of crushing and near crushing situations within 24h after birth of first piglet (BFP) was significantly decreased in pens with access to straw (F ₁,₂₅ =4.50, P =0.04), whereas there was no significant influence of cover on this variable. Neither the number of scan intervals with lateral lying nor the number of postural changes were significantly influenced by cover or straw. In conclusion, the sows did select a specific nest site within the farrowing pen, but neither the choice of nest site nor the temporal consistency of staying in the nest were significantly affected by cover or ad libitum access to straw. Access to a covered area increased the occurrence of nest-building behaviour whereas access to straw reduced the number of near crushing situations.