Abstract
Observations of play in animals have been suggested as a promising indicator of positive emotions and thus of positive animal welfare. However, if play can follow the proposed reward cycle concept where animals estimate and value reward differently in different phases of the cycle (anticipation, consummation and post-consummation) is unclear. To investigate if a reward cycle for play exists in growing pigs, we carried out an exploratory study where pigs were tested when they were naïve to a reward cycle test (first occasion) against when they were accustomed to going through the test after having the access to an open play arena with objects. Forty undocked pigs were housed in a weaner stable with two castrated males and two females per pen. Within each litter, we randomly selected and tested one male and one female test pig, each being tested as naïve or accustomed to the testing environment. The first week the pigs (n= 20) were tested four times and regarded as naïve during the first day. After that they were regarded as accustomed, and were tested twice a week for 3 weeks. We observed the behavior of the tested pairs in three subsequent stages: (1) in a holding pen 3 min, (2) in a play arena 15 min, and (3) in their home pen 10 min. When accustomed, pigs showed more locomotor play, social interactions and standing, and a tendency of more orientation toward the play arena and exploring bars facing the play arena (i.e., reward-seeking behavior) in the holding pen than when they were naïve, suggesting an anticipation to enter the play arena. Performing high numbers of object play in all sessions, and for accustomed pigs more exploration and social interaction, but less locomotor play and walking in the play arena may suggest consumption of play and exploration. Finding more lying and sitting in accustomed pigs, but less standing and walking in the home pen is in line with the previous hypothesis of the post-consummatory behaviors. Our study showed mixed results for the existence of a reward cycle for play in pigs and generated questions for future research.
Highlights
Positive emotions are suggested to be shown in a rewarding environment, which elicit a cognitive appraisal in the central nervous system that is followed by physiological and behavioral reactions (Boissy et al, 2007)
In order to explore if the results from this study indicates the existence of a reward cycle for play in commercial pigs we have put together the results where naïve pigs differed significantly from the accustomed pigs (Figure 5)
The main findings that could support the existence of a reward cycle was that pigs accustomed to enter the play arena showed more “locomotor play,” “social interactions,” “explore bar,” “stand,” and tended to show more “orient arena,” but showed less “walk” in the holding pen than naïve pigs and these behaviors could indicate that they anticipated to access the play arena
Summary
Positive emotions are suggested to be shown in a rewarding environment, which elicit a cognitive appraisal in the central nervous system that is followed by physiological and behavioral reactions (Boissy et al, 2007). Reward Cycle of Play in Pigs to obtain, i.e., what an animal “wants.” If animals’ likes to perform play behavior it may be possible to investigate if the animals will show behaviors indicating that it wants to play. The elements are: (1) positive emotions (the capacity of animals to experience positive emotions), (2) positive affective engagement (seeks to create a link between positive emotions and behaviors animals are motivated to engage in), (3) Quality of Life (QoL, acts to give PAW a role in defining an appropriate balance of positive over negative emotions) and (4) Happiness (brings a full life perspective to PAW). Play behaviors may induce positive emotions that animals are motivated to engage in, and in the process of playing increase QoL and bring happiness to animals
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