Evaluation of changes in architecture of the stratum internum of the hoof wall from fetal, newborn, and yearling horses.

This research evaluated the morphological changes in the inner layer of the horse’s hoof wall, known as the stratum internum, from the fetal stage to the first year of life. The study concluded that significant changes occur shortly after birth, especially in the form and density of the epidermal laminae, which affect the shape and structure of the hoof.

Research Methodology

• The study utilized the hooves from 27 near-term equine fetuses, 19 newborn foals, and 8 yearlings. These subjects allowed the researchers to compare the morphology of the hoof wall at different stages of the horse’s life.
• The primary epidermal laminae (PEL) of the stratum internum, tiny leaf-like structures connecting the outer and inner layers of the hoof wall, were carefully examined for any evidence of architectural changes. The research looked at variations in the PEL’s appearance, distribution, and density across the hoof wall.

Key Findings

• In near-term fetuses, the PEL exhibited a homogeneous appearance with a symmetric distribution around the hoof wall. This uniformity didn’t show significant differences in PEL density between the toe and quarters of the hoof.
• The soonest significant aesthetic and architectural changes were detected after birth. Transformations in PEL structure, such as branching at the toe, started to form within the first few weeks. This contributed to the substantial increase in PEL density at the toe compared to the quarters.
• In yearlings, the researchers observed that the PEL’s architecture was significantly different from that of younger foals. The PEL density was notably larger at the toe than the quarters and distinct PEL densities were associated with the unique conformation of the foot.
• Different PEL densities were identified in the toe, medial and lateral quarters of the hoof. However, there was no significant difference in PEL densities between the front and back hooves in any of the groups studied.

Conclusions and Implications

• The findings demonstrated that the inner layer of the hoof wall undergoes numerous morphologic changes after birth. This is characterized by the branching of PEL and a greater PEL density at the toe than the quarters.
• In an asymmetric foot, more PEL were found on the sloping side than the steep side. This suggests that PEL growth might occur by division as well as by the horse’s natural cell division process or ‘mitosis’ from the coronet, the region where the hoof wall grows.
• The indication of wall stress being associated with increased PEL density suggests that the horse’s external environment could play a role in influencing the hoof wall’s structure, which may have implications for hoof health management practices.