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Scientific reports2025; 15(1); 5373; doi: 10.1038/s41598-025-89329-x

Facial expressions during compound interventions of nociception, conspecific isolation, and sedation in horses.

Abstract: Facial expressions in prey animals such as equines can convey information regarding their internal state and are therefore often used as cues for welfare and pain evaluation. The state of pain is commonly compared to a neutral state with little consideration given to other experiences that could affect the animal, although this situation is rare outside of experimental contexts. To evaluate the effect of managerial contexts on facial expressions from a nociceptive input, conspecific isolation and sedation with known physiological effects were compared to compound states of nociception. Using an anatomically based facial action coding system and a short acting pain model, patterns of facial activity could discriminate between horses experiencing conspecific isolation, sedation, and a nociceptive stimulus separately. Nociception occurring together with conspecific isolation could not be discriminated from the conspecific isolation alone, and compound nociception and sedation could not be discriminated from control. While blinking frequency demonstrated potential to be a valuable marker when evaluating a nociceptive stimulus in sedated horses, careful consideration must be given to the biological interpretation of facial expressions during situations where managerial or drug effects may be present.
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Publication Date: 2025-02-13 PubMed ID: 39948238PubMed Central: PMC11825850DOI: 10.1038/s41598-025-89329-xGoogle Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The study is about understanding horse facial expressions in different circumstances including pain, isolation from peers, and sedation, and how these expressions help to provide clues to their wellbeing.

Objectives of the Study

  • The research looks into the evidence of how prey animals like horses express their internal state such as pain or stress visually through facial expressions.
  • The study aims to scrutinize whether the facial expressions caused by pain, conspecific isolation, and sedation are distinguishable. It also evaluates how compound situations (multiple stimuli at once) affect these expressions.

Methodology

  • The researchers used an anatomically based facial action coding system and implemented a short-acting pain model to observe the patterns in horse facial expressions.
  • The reactions to three different situations – conspecific isolation, sedation, and a nociceptive stimulus – were observed and compared separately and in compound variations.

Findings

  • The study found out that the horses were responding differently to each circumstance when they happened separately. The facial expressions permitted identification of the situation the horse was in.
  • However, when the nociceptive stimulus happened alongside conspecific isolation, the researchers could not distinguish any difference in facial expressions from conspecific isolation alone.
  • Similarly, no discernible difference was found in facial expressions when horses were subjected to a compound situation of nociceptive stimulus and sedation when compared to control.
  • One noteworthy discovery was that blinking frequency could be a useful marker to identify a nociceptive stimulus when the horses are sedated.

Conclusion

  • The study concludes that although facial expressions are a useful indicator of a horse’s internal condition, their interpretation requires caution particularly during managerial or drug effect situations.
  • In addition, more specific markers, like blinking frequency, could be used to detect pain in sedated horses, but more exploration is needed in this area.

Cite This Article

APA
Lundblad J, Rhodin M, Hernlund E, Bjarnestig H, Hidén Rudander S, Haubro Andersen P. (2025). Facial expressions during compound interventions of nociception, conspecific isolation, and sedation in horses. Sci Rep, 15(1), 5373. https://doi.org/10.1038/s41598-025-89329-x

Publication

Scientific reports
ISSN: 2045-2322
NlmUniqueID: 101563288
Country: England
Language: English
Volume: 15
Issue: 1
Pages: 5373
PII: 5373

Researcher Affiliations

Lundblad, Johan
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, PO Box 7023, Uppsala, 750 07, Sweden. Johan.Lundblad@slu.se.
Rhodin, Marie
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, PO Box 7023, Uppsala, 750 07, Sweden.
Hernlund, Elin
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, PO Box 7023, Uppsala, 750 07, Sweden.
Bjarnestig, Hanna
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, PO Box 7023, Uppsala, 750 07, Sweden.
Hidén Rudander, Sara
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, PO Box 7023, Uppsala, 750 07, Sweden.
Haubro Andersen, Pia
  • Department of Animal Biosciences, Swedish University of Agricultural Sciences, PO Box 7023, Uppsala, 750 07, Sweden.

MeSH Terms

  • Animals
  • Horses
  • Facial Expression
  • Nociception / drug effects
  • Pain / drug therapy
  • Male
  • Female
  • Behavior, Animal / drug effects

Conflict of Interest Statement

Declarations. Competing interests: The authors declare no competing interests.

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