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Scientific reports2024; 14(1); 129; doi: 10.1038/s41598-023-50383-y

Changes in the equine facial repertoire during different orthopedic pain intensities.

Abstract: A number of facial expressions are associated with pain in horses, however, the entire display of facial activities during orthopedic pain have yet to be described. The aim of the present study was to exhaustively map changes in facial activities in eight resting horses during a progression from sound to mild and moderate degree of orthopedic pain, induced by lipopolysaccharides (LPS) administered in the tarsocrural joint. Lameness progression and regression was measured by objective gait analysis during movement, and facial activities were described by EquiFACS in video sequences (n = 348, total length 892.5 min) of the horses obtained when resting in their box stalls. Predictive modeling identified 16 action units and action descriptors, related to ears, eyes, and lower face. Lower lip depressor (AU16), lips part (AU25), half blink (AU47), single ear forward (SEAD101) and single ear rotator (SEAD104) were selected as co-occurring significantly more in horses with pain than in horses without pain. The major change in co-occurring facial activities occurred in the transition from no pain to mild pain. In conclusion, resting horses with induced orthopedic pain showed a dynamic upper and lower facial repertoire and the relationship between level of pain intensity and facial activity appears complex.
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Publication Date: 2024-01-02 PubMed ID: 38167926PubMed Central: PMC10762010DOI: 10.1038/s41598-023-50383-yGoogle Scholar: Lookup
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Summary

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The research article discusses a study that catalogued horse facial expressions to determine their significance in identifying various levels of induced orthopedic pain.

Study Objective

  • The study objective was to comprehensively record and analyze changes in a horse’s facial activities during orthopedic pain of varying degrees. The focus was on orthopedic pain-induced facial movements yet to be documented.

Methods

  • Eight horses in a resting state were selected for the study.
  • Pain was artificially induced in the horses through the administration of lipopolysaccharides (LPS) in the tarsocrural joint (ankle joint).
  • The intensity of orthopedic pain was varied from ‘sound’ (no pain) to ‘mild’ and ‘moderate’ degrees. Regular gait analysis helped monitor the progression and regression of lameness.
  • A total of 348 video sequences were captured when the horses were resting in their stalls and their facial activities were minutely examined with the EquiFACS method.

Findings

  • Using predictive modeling, 16 action units and action descriptors associated with the ears, eyes, and lower face were identified.
  • Five distinctive facial activities (Lower lip depressor (AU16), lips part (AU25), half blink (AU47), single ear forward (SEAD101) and single ear rotator (SEAD104)) were found to manifest significantly more in horses experiencing pain.
  • A substantial adjustment in the combination of facial activities was noticed when horses transitioned from a pain-free state to a state of mild pain.

Conclusion

  • Horses at rest, subjected to artificially induced orthopedic pain, showed a dynamic range of upper and lower facial displays.
  • The correlation between the level of pain intensity and facial activity was discovered to be complex.

Cite This Article

APA
Ask K, Rhodin M, Rashid-Engström M, Hernlund E, Andersen PH. (2024). Changes in the equine facial repertoire during different orthopedic pain intensities. Sci Rep, 14(1), 129. https://doi.org/10.1038/s41598-023-50383-y

Publication

Scientific reports
ISSN: 2045-2322
NlmUniqueID: 101563288
Country: England
Language: English
Volume: 14
Issue: 1
Pages: 129
PII: 129

Researcher Affiliations

Ask, Katrina
  • Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden. katrina.ask@slu.se.
Rhodin, Marie
  • Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Rashid-Engström, Maheen
  • Univrses AB, Stockholm, Sweden.
Hernlund, Elin
  • Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Andersen, Pia Haubro
  • Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden.

MeSH Terms

  • Animals
  • Horses
  • Pain Measurement / veterinary
  • Horse Diseases
  • Pain / veterinary
  • Gait
  • Facial Expression
  • Lameness, Animal

Grant Funding

  • 2106-01760 (MR) / Svenska Forskningsru00e5det Formas

Conflict of Interest Statement

The authors declare no competing interests.

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