Histological comparison of the lamellar tissue of Iberian origin breed horses created in semi-feral conditions or in an intensive system

Abstract

Although the external conformation of wild horse hooves has been proposed as an ideal model for domesticated modern horses, histological signs of laminitis have been reported among them. With the hypothesis that the lamellar tissue of horses of Iberian origin raised in semi-feral is healthier than those raised in an intensive management system (stall confinement and high-calorie diet intake), the objective was to compare their lamellar tissues. Lamellar tissue samples were taken from the forelimb hoof of eight domesticated Mangalarga Marchador (MM) horses and from six semi-feral Marajoara (MJ) and Puruca (MP) horses. Primary epidermal lamella (PEL) and secondary epidermal lamella (SEL) were measured (length and width) in several regions, and their shapes were morphologically classified into different types. Breed groups were compared using analysis of variance, followed by Tukey or Dunn tests (P<0.05). Early signs of laminitis such as abnormal keratinization of the abaxial primary dermal lamella, tapered tips of the axial PELs, pointed tips of the SEL, nuclei condensation, and abnormal spatial orientation of the secondary epidermal basal cells (SELBC), were seen only in MM horses. MP horses had a greater interface of epidermis/dermis contact than MJ horses and more rounded nuclei in the round SELBC than MM horses. In agreement with the study hypothesis, semi-feral MJ and MP horses’ lamellae were classified as healthier than MM horses, which showed early signs of endocrinopathic laminitis.

Rewilded horses in European nature conservation – a genetics, ethics and welfare perspective

“…Instead, pasture based diet, daily distance travelled and soft substrate may explain the observed differences in laminitis prevalence between feral horses in different parts of the world. Thirdly, a diet devoid of non-structural carbohydrates, daily unlimited exercise, and exposure to the elements may prove to be protective against the development of endocrinopathic laminitis (Malacarne et al 2023). Additionally, the natural weight loss and weight gain cycle typical of feral herbivores (De Roos et al 2009) may be a countermeasure to the periods of increased non-structural carbohydrate rich food consumption during the periods of abundance of vegetation (Górecka-Bruzda et al 2020).…”