A topographic analysis of skin thickness in horses

Abstract

A systematic study of regional skin thickness in different types of horses has not yet been described. Knowledge about regional skin thickness has long been used in human medicine to optimise wound care and skin grafting outcomes and similar knowledge could prove useful in equine wound management. The objective of the current study was to report the topographical variation in skin thickness of Warmblood (WB) and Coldblood (CB) type horses and to compare different methods for measuring skin thickness. Horses free of skin conditions and euthanised for reasons unrelated to this study were included. Skin biopsies were collected post-mortem from 28 locations in 9 WB horses and skin biopsy thickness was measured using a digital calliper. In 6/28 locations, skin fold measurements using a micrometer were also obtained. In another cohort comprising 8 WB and 10 CB horses, skin biopsies were harvested from 6 locations for histologic skin thickness measurements. Descriptive statistics revealed large topographical variation in skin thickness. A mixed effect model assessing the effect of breed and sampling location demonstrated that skin thickness was significantly higher in CBs than WBs (P < 0.001). At the mid-15th rib and between the forelimbs, there was strong correlation between calliper and skin fold measurements (ρ 0.72 and 0.74, respectively), whereas correlation was very strong at the ventral abdomen (ρ 0.83). In conclusion, this study demonstrates large topographical variations in skin thickness in horses, and significant differences between horse types. Skin fold measurements may estimate skin thickness at the ventral abdomen.

Supplementary Information: The online version contains supplementary material available at 10.1007/s11259-026-11124-4.

Keywords: Anatomy; Histology; Horse; Skin grafting; Skin thickness.

Fig. 1

Whole-slide image sections showing the three levels that were measured histologically. (A) The epidermis was measured from the top of the stratum corneum to the basement membrane (a). (B) The upper dermis was measured from the top of the stratum corneum to the deepest follicular units (b), whereas the whole biopsy was measured from the top of the stratum corneum to the dermal-subcutaneous junction (c). All measurements were done perpendicular to the epidermal surface

Fig. 2

A graphical heatmap presentation of the topographical variations in skin thickness along the equine body and extremities based on biopsy calliper measurements in 9 Warmblood horses, across 28 locations. Figure created using gimp.org and biorender.com. (Olsen, H. 2026; https://BioRender.com/ktb9hg1)

Fig. 3

Box plot of skin thickness across multiple locations in forelimbs (blue boxes) and hind limbs (orange boxes). In both forelimbs and hind limbs, skin thickness generally increased from proximal to distal. Asterisk denote significant differences between fore- and hindlimbs (* P = 0.0002; ** P = 0.0002; *** P < 0.0001)

Fig. 4

Box plot of whole biopsy histologic skin thickness measured at 6 different locations. Blue boxes: Coldblood (CB) type horses (n = 10). Orange boxes: Warmblood (WB) type horses (n = 8). Asterisk denote significant differences between the two breeds (P < 0.001)

Fig. 5

Box plot of whole biopsy histologic skin thickness and macroscopic skin thickness measured at 6 different locations in WB horses, corresponding to locations 1–6 in Table 3 (histologic measurement), and locations 4, 12, 10, 14, 21 and 27 in Table 1 (calliper measurements). Blue boxes: macroscopic (calliper) measurements from 9 Dutch Warmblood horses. Orange boxes: histologic measurements from 8 Warmblood type horses. Asterisk denote significant differences between the two measuring methods (P < 0.001)