Researchers in the Equine Foot Laboratory at Michigan State University recently examined the inner hoof wall in fetal, newborn and yearling horses to describe structural changes that occur in the epidermal laminae from fetal development to yearling age.
Hooves from 27 fetuses, 19 foals and 8 yearlings were presented to the diagnostic laboratory for reasons unrelated to the hoof. The hooves were sectioned and examined visually and microscopically. The size, shape and density of the primary epidermal laminae were described.
In the fetus, the circumference of the feet was larger at the coronary band compared with the ground surface. They showed medial-lateral symmetry and the primary epidermal laminae were uniform in appearance and distributed symmetrically around the hoof.
After the first few weeks of age, branching of the laminae was apparent in the toe and laminar density increased significantly in the toe compared with the quarters.
Yearling feet had a typical overall appearance with a larger circumference at the ground surface, more sloping lateral hoof walls and steeper medial hoof walls. Shape of the lamina was more variable in yearlings, with more branching and greater laminar densities in the toe and lateral wall than seen in foals.
The authors hypothesize that changes in laminar shape and density are part of the normal growth process, as well as an adaptive response to loading by external environmental forces and to internal structural forces. Unfortunately, they also suggest this adaptive growth of the hoof wall suggests that…