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Several studies suggest that animals in a negative emotional state are more sensitive to reward losses as shown by behavioural and neurophysiological responses. In a successive negative contrast (SNC) test, reward losses are induced by decreasing the size of the reward for a task for which animals have been trained. is SNC paradigm has not been widely used in pigs. It is well known that environmental enrichment positively inuences the welfare of pigs, and may induce a more optimistic emotional state, which could reduce their sensitivity to reward losses. We studied pigs in barren (B) or enriched (E) housing, experiencing either a switch in housing conditions at 7 weeks of age or not (4 treatment groups: EE, EB, BE, BB, n=8 pens per group) in an SNC runway task. We hypothesized that B housed pigs, particularly those that changed from E to B housing, would show an enhanced sensitivity to reward losses. One pig per pen was trained to run a 24.6 m U-shaped runway for 6 pieces and one for 1 piece of apple. Each pig received 3 trials per day, with a maximum of 120 sec/trial. Latency to start eating the reward was recorded, and the average was calculated per day. Aer 11 days, all pigs received 1 piece of apple only for another 11 days (reward shi: 6-1 vs 1-1 reward group), i.e. the group originally receiving 6 pieces of apple experienced a reward loss. Eects of pre-housing, post-housing, (original) reward size, day and interactions were analysed using mixed models with a random eect of animal. Fiy-one pigs were successfully trained. Before the reward shi, over the rst 11 days, pre-housing × post-housing × reward size aected the average run-time (P<0.05). All BB pigs ran slower than other pigs (BB: 59.3±2.8; BE: 35.9±1.7; EB: 39.6±2.2; EE: 40.9±2.2, P<0.05), without any other signicant pairwise dierences. Analysis per treatment revealed, however, that EB 6-reward pigs were faster than the 1-reward pigs. Overall latency was higher on the last days (P<0.001). Aer the reward size shied to 1 on day 12, pre-housing × post-housing aected the latency (P<0.001). Post hoc analysis showed that again, BB pigs were slower than other pigs (BB: 88.2±2.7; BE 62.3±2.3; EB: 57.3±2.3; EE: 70.4±2.6, P<0.001), and EB pigs were faster than EE pigs (P<0.05). Pigs ran slower aer than before the reward shi (P<0.001). Nevertheless, pigs in the 6-1 group ran slower than pigs in the 1-1 group aer the reward shi (6-1: 73.9±2.0; 1-1: 66.4±1.8, P<0.05), suggesting that pigs are sensitive to a loss in reward size. is was, however, irrespective of housing given the lack of interactions with reward size. We conclude that housing aected the latency to run down a runway for a reward in pigs, which can indicate a lower motivation in the BB pigs, an eect that was absent in the B pigs that switched to enriched housing (BE pigs). We found, however, no evidence that housing or a switch in housing conditions aected the sensitivity to reward loss.
|Title of host publication||Proceedings of the 52nd Congress of the International Society for Applied Ethology|
|Subtitle of host publication||Ethology for health and welfare|
|Editors||Michael Cockram, Tarjei Tennessen, Luis Bate, Renée Bergeron, Sylvie Cloutier, Andrew Fisher, Maria Hötzel|
|Place of Publication||Wageningen, The Netherlands|
|Publisher||Wageningen Academic Publishers|
|Publication status||Published - 2018|
|Event||ISAE 2018: 52nd Congress of the International Society for Applied Ethology - Charlottetown, Canada|
Duration: 30 Jul 2018 → 3 Aug 2018
|Period||30/07/18 → 3/08/18|
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- 1 Oral presentation
Effects of (a switch in) enriched vs barren housing on the response to reward loss in pigs in a negative contrast test3 Aug 2018
Activity: Talk or presentation › Oral presentation › Other