Fond of each other: Positive human-animal interactions

Positive social interactions have received little scientific interest compared to aggression and other socio-negative behaviours. Positive social interactions can improve longevity, health and well-being. Nevertheless, the biological mechanisms through which this occurs remain surprisingly poorly understood. This project investigates how positive human-animal interactions benefit animal welfare. We will achieve this aim by 1) Studying the type of behaviours that characterise positive interactions, 2) Identifying the specific roles of different neurotransmitters, and 3) Elucidating the effects of long-term positive interactions on the brain and the immune system of the animal. These studies will be conducted with farm pigs, as they are highly social domesticated animals that are eager to interact with humans. To clarify the pathways through which positive human-animal interactions benefit animals, the project relies on a multi-disciplinary approach combining animal behaviour, physiology, proteomics, neuroscience and psychoneuroimmunology.

Human-animal interactions can have a profound impact on animal welfare. Nevertheless, the biological mechanisms through which this occurs remain surprisingly poorly understood. This project investigates how positive human-animal interactions can benefit animal welfare. We achieved this aim by 1) Studying the type of behaviours that characterise positive interactions, 2) Identifying the specific roles of different neurotransmitters, and 3) Elucidating the effects of long-term positive interactions on the brain and the immune system of the animal. These studies were conducted with farm pigs, as they are highly social domesticated animals that are eager to interact with humans. To clarify the pathways through which positive human-animal interactions benefit animals, the project relies on a multi-disciplinary approach combining animal behaviour, physiology, proteomics, neuroscience and psychoneuroimmunology. In study 1, we compared the reaction of pigs toward free-form contact, when pigs were free to interact as they wished with a human, and imposed contacts, when the human decided when to apply gentle physical contacts on the pigs. The results showed no clear preference for imposed contact vs free-form interactions in the pigs, based on behavioural indicators of wanting to interact and emotions. However, changes in a familiar human's behaviour increased attentiveness and possibly induced frustration in the pigs as this may have differed from what they expected or have been used to. This study highlighted the importance of the methodology used to study human-animal interactions. In study 2a, oxytocin release in the pigs was higher after encounters with unfamiliar humans, compared to familiar humans. However, none of the neurotransmitters analysed (oxytocin, beta-endorphin, dopamine and serotonin metabolites ) showed significant changes between the humans delivering positive contacts vs. ignoring the pigs, although these preliminary results are still being analysed. In study 2 b, the oral administration of a dopamine receptor antagonist prior to interacting with a familiar human significantly increased the time for the pigs to approach and touch the humans, supporting that dopamine is important for the pigs' motivation to interact. However, the intranasal administration of an opioid receptor antagonist had no effect on the time pigs spent in contact with the human, contrary to our prediction that blocking opioids would decrease the pleasurability of the interaction. In study 3, long-term and repeated positive human-animal interactions over 9 weeks did not provide noticeable improvement of the immune response of pigs, but it changed the pigs' brain response and suggest that stroking by a human is perceived as a social and pleasurable event. Overall, this project helps to develop novel approaches to study human-animal interactions, and the results deepen our understanding of the biological effects of interacting positive with animals on the animals themselves.