Segment-related specifities of the equine hoof - Part 1: Structural and functional variants

Horn samples from all segments of the hoof of fifteen warm blooded horses (Equus caballus) and ten Przewalski horses (Equus ferus przewalskii) were examined transmission and scanning electron microscopically. The horn masses from the different hoof segments showed numerous variations regarding form and structure which were related to segment-specific functions. The lamellar horn cells from the wall segment displayed parallel horny tralbeculae consisting of keratin filaments coated by keratin filament associated proteins (KFAP) and linked by disulfide bonds. In the horny tubules, on the other hand, three-dimensional arrangement of horny tralbeculae is discernible in order to withstand pressure forces from different directions. The lamellar horn cells and the tubular horn cells of the inner coronary horn layer appear spongiform and contain water in their precast excavations. Addtionally, a diffuse water storage fakes place at the different horn cell components (cytokeratins, KFAP and intercellular cementing substance). A third manner of wafer storage prevails in the perioplic horn where water droplets are bound in the intercellular cleft. This results in a considerable water binding capacity of 71,36 % water content at maximum wafer saturation. The differing water content greatly influences the mechanical capacities of the horn (hardness, firmness and elasticity) as well as the horn qualify.