The influence of satiety on the motivation of stall-housed gestating sows to exit their stall

The welfare of stall-housed gestating sows is a point of public concern worldwide. In Canada, the Code of Practice for the Care and Handling of Pigs (2014) proposed allowing the operation of existing stall barns after 2024, if bred female pigs are given opportunities for greater freedom of movement. Previous research demonstrated that sows are motivated to exit their stall, but when out of their stall, primarily perform exploration/feed searching behaviour. This suggests that having an opportunity to exercise per se may not be as important for sows, and rather, feeding motivation in these restrict fed sows may play a strong role to exit their stall to explore and seek feed. Therefore, the objective of this study was to explore whether the motivation of stall-housed gestating sows (n = 42) to leave their stall is influenced by satiety. Sows were assigned to one of three treatments: control (C), fed a standard ration (2.3 kg of feed/sow) only; moderately satiated (0.5 HF), standard ration and 50% of their ad-lib high fibre (HF) intake; fully satiated (ad-lib HF), standard ration and unlimited access to HF. Sows were trained to use an operant panel containing two buttons: i) active button (AB - push counts resulted in a reward of movement), ii) dummy button (push counts not rewarded). The required number of AB presses during a testing session increased by 50% each day. Animal behaviour once out of the stall was continuously video recorded. Control sows showed a greater highest price paid (HPP, maximum AB push counts in one session) than ad-lib HF sows, with 0.5 HF sows being intermediate (C: 94.43 +/- 18.21, 0.5 HF: 66.43 +/- 5.88, ad-lib HF: 59.14 +/- 23.65; F-2,F-39 = 3.38, P = 0.044, mean HPP +/- SEM). When out of the stall, sows from all treatments spent the greatest proportion of time performing exploratory behaviour (E) and an equal and lower proportion of time in locomotion (L) and in snout to snout contact (S) (L: 0.20 +/- 0.02, E: 0.64 +/- 0.03, S: 0.16 +/- 0.02; F-3,F- 162 = 279.00, P < 0.001, mean proportion of time +/- SEM). Results suggest that stall-housed sows are motivated to exit their stalls, and the strength of motivation is influenced by satiety. Behavioural results indicate the importance of exploratory behaviour and suggest the presence of a strong motivation to exercise and also motivation for social contact.