A comparative neuro-histological assessment of gluteal skin thickness and cutaneous nociceptor distribution in horses and humans

Lydia Tong, Melinda Stewart, Ian Johnson, Richard Appleyard, Bethany Wilson, Olivia James, Craig Johnson, Paul McGreevy*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The current project aims to build on knowledge of the nociceptive capability of equine skin to detect superficial acute pain, particularly in comparison to human skin. Post-mortem samples of gluteal skin were taken from men (n = 5) and women (n = 5), thoroughbreds and thoroughbred types (mares, n = 11; geldings, n = 9). Only sections that contained epidermis and dermis through to the hypodermis were analysed. Epidermal depth, dermal depth and epidermal nerve counts were conducted by a veterinary pathologist. The results revealed no significant difference between the epidermal nerve counts of humans and horses (t = 0.051, p = 0.960). There were no significant differences between epidermal thickness of humans (26.8 µm) and horses (31.6 µm) for reference (left side) samples (t = 0.117, p = 0.908). The human dermis was significantly thinner than the horse dermis (t = −2.946, p = 0.007). Epidermal samples were thicker on the right than on the left, but only significantly so for horses (t = 2.291, p = 0.023), not for humans (t = 0.694, p = 0.489). The thicker collagenous dermis of horse skin may afford some resilience versus external mechanical trauma, though as this is below the pain-detecting nerve endings, it is not considered protective from external cutaneous pain. The superficial pain-sensitive epidermal layer of horse skin is as richly innervated and is of equivalent thickness as human skin, demonstrating that humans and horses have the equivalent basic anatomic structures to detect cutaneous pain. This finding challenges assumptions about the physical capacity of horses to feel pain particularly in comparison to humans, and presents physical evidence to inform the discussion and debate regarding the ethics of whipping horses.

Original languageEnglish
Article number2094
Pages (from-to)1-15
Number of pages15
JournalAnimals
Volume10
Issue number11
DOIs
Publication statusPublished - 11 Nov 2020

Bibliographical note

Copyright the Author(s) 2020. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • Dermis
  • Epidermis
  • Innervation
  • Nerve cell counts
  • Pain
  • Whipping

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