Manipulable object and human contact: preferences and modulation of emotional states in weaned piglets

Abstract

1Enriching the life of farm animals is an obligation in intensive farming conditions. In pigs, manipulable materials are mandatory when no bedding is available. Like manipulable objects, positive human interactions might be considered as enrichment, as they provide the animals occasions to interact, increase their activity and lead to positive emotional states. In this study, we investigated how weaned piglets perceived a manipulable object, and a familiar human. After a similar familiarization to both stimuli, twenty-four weaned piglets were tested for a potential preference for one of the stimuli and submitted to isolation/reunion tests to evaluate the emotional value of the stimuli. We hypothesized that being reunited with a stimulus would attenuate the stress of social isolation and promote positive behaviors, and even more that the stimulus has a positive emotional value for piglets. Although our behavioural data did not allow to show a preference for one of the stimuli, piglets approached more often the human and were observed laying down only near the human. Using behavioural and bioacoustic data, we showed that reunion with the human decreased more the time spent in an attentive state and mobility of piglets than reunion with the object, and isolation. Vocalizations differed between reunions with the object and the human, and were different from vocalizations during isolation. The human presence led to higher frequency range, more noisy and shorter grunts. Finally, both stimuli decreased the isolation stress of piglets, and piglets seemed to be in a more positive emotional state with the human compared to the object. It confirms the potential need for positive human interactions to be used as pseudo-social enrichment in pigs.