Effects of (a switch in) enriched vs barren housing on the response to reward loss in pigs in a negative contrast test

Lu Luo, I. Reimert, Sharine Smeets, E.N. de Haas, H.K. Parmentier, B. Kemp, J.E. Bolhuis

Research output: Chapter in Book/Report/Conference proceedingAbstract


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 inuences 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. Aer 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. Eects of pre-housing, post-housing, (original) reward size, day and interactions were analysed using mixed models with a random eect of animal. Fiy-one pigs were successfully trained. Before the reward shi, over the rst 11 days, pre-housing × post-housing × reward size aected 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 signicant pairwise dierences. 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). Aer the reward size shied to 1 on day 12, pre-housing × post-housing aected 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 aer than before the reward shi (P<0.001). Nevertheless, pigs in the 6-1 group ran slower than pigs in the 1-1 group aer 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 aected the latency to run down a runway for a reward in pigs, which can indicate a lower motivation in the BB pigs, an eect 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 aected the sensitivity to reward loss.
Original languageEnglish
Title of host publicationProceedings of the 52nd Congress of the International Society for Applied Ethology
Subtitle of host publicationEthology for health and welfare
EditorsMichael Cockram, Tarjei Tennessen, Luis Bate, Renée Bergeron, Sylvie Cloutier, Andrew Fisher, Maria Hötzel
Place of PublicationWageningen, The Netherlands
PublisherWageningen Academic Publishers
ISBN (Electronic)9789086868704
ISBN (Print)9789086863228
Publication statusPublished - 2018
EventISAE 2018: 52nd Congress of the International Society for Applied Ethology - Charlottetown, Canada
Duration: 30 Jul 20183 Aug 2018


OtherISAE 2018

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