Facial expression and oxytocin as possible markers of positive emotions in horses

Abstract

Behavioural and physiological markers of discrete positive emotions remain little investigated in animals. To characterise new markers in horses, we used tactile stimulations to induce emotional situation of contrasting valence. In the Gentle grooming group (G, N = 13) horses were gently groomed during 11 sessions on the body areas they appreciated the most. Horses in the Standard grooming group (S, N = 14) were groomed using a fixed procedure, reported to induce avoidance reactions in some horses. At session 11, G horses expressed significantly more contact-seeking behaviours than S horses, which expressed significantly more avoidance behaviours. This result suggests positive emotions in G horses and negative emotions in S horses. Blood cortisol, oxytocin, heart rate and heart rate variability never differed between before and after the grooming session. However, after the 11 sessions, basal oxytocin levels were lower in the G than in the S group. This difference was unexpected, but supports studies showing that a low level of basal oxytocin could be a marker of better well-being. Analyses of facial expressions during grooming revealed significant differences between groups. These expressions appear to be more sensitive than behavioural indicators because they alone enabled differentiating emotions according to the group when horses were re-exposed to neutral grooming one year after the treatment.

Female horses spontaneously identify a photograph of their keeper, last seen six months previously

“…Another study, conducted on only three horses showed that they recalled correctly complex problem-solving strategies seven years later 23 . Regarding the more specific human-animal relationship, horses could remember interactions they had had with human beings five months 26 , or even a year previously 25 . The present study shows that beyond remembering what they have learned or the interactions they have had with humans, horses also have an excellent memory of people and particularly of their faces.…”

“…Indeed, it can correctly recall the conditioning procedure several years later 23,24 . In addition, horses can also remember the type of relationship (positive or negative) they had experienced with a human several months after the interaction 25,26 . However, no information is available about a horse's potential capacity to remember faces over time.…”

Effects of Different Stroking Styles on Behaviour and Cardiac Parameters in Heifers

“…Therefore, reacting in a flexible way to the animal's behavioural indications of preference, and consequently stroking different body areas, would mimic the social behaviour of cattle more closely and might lead to more positive reactions. While studies in horses have shown that grooming styles reacting to the animals' signals lead to more positive reactions [23], there is no study investigating reactive stroking treatments in cattle yet.…”

Talking to Cows: Reactions to Different Auditory Stimuli During Gentle Human-Animal Interactions

“…As this experiment did not include a treatment where the animals were stroked without any auditory stimulation, we cannot infer any information on whether gentle talking in general enhances or diminishes the positive effects of stroking, but the results are very similar to our previous study, where the animals were stroked without acoustic stimulation. Stroking can elicit quite strong effects on physiology and behavior in different species (rats: Holst et al, 2005 ; cows: Schmied et al, 2010 ; cats: Gourkow et al, 2014 ; lambs: Coulon et al, 2015 ; horses: Lansade et al, 2018 ), which might exceed possible consequences of small differences in auditory stimuli. Regarding the absence of significant differences in behavior, it seems plausible that the heifers did not discern the two auditory stimuli, at least not to an extent where it would have affected their behavior.…”