Micromechanics of the equine hoof wall: optimizing crack control and material stiffness through modulation of the properties of keratin.

The research article investigates the mechanics of horse hoof walls looking into specifics such as its structural components, their roles, and modulation to optimize crack control and material stiffness. The findings suggest the hoof wall properties are achieved by varying specific structural components, adding to our understanding of horse hoof wall biomechanics.

Study Overview

• The study entails both macroscale and microscale testing on various samples derived from different parts of the equine hoof wall.
• Landmark findings include a significant difference in stiffness between inner-wall tubules and intertubular material samples, thereby demonstrating the crucial stiffening role the inner-wall tubules play.
• Furthermore, the mid-wall tubules do not significantly reinforce the longitudinal axis—their material properties align closely with the intertubular material from the same region.

Microscale Testing

• Microscale testing was performed on keratin strands from the inner-wall tubules, intertubular materials, and mid-wall strands to estimate the stiffness of other structural components.
• Testing illustrates variance in the properties of the keratin composite – the molecular building block of the hoof wall – across the thickness of the wall.
• Based on the testing, two components of the nanoscale keratin composite were determined to have different stiffness values: the hydrated matrix and the intermediate filament (IF).

Birefringence Measurements

• Birefringence measurements from the inner wall and mid-wall regions validate the results from the microscale tests—indicating uniformity in volumes of keratin IF but with changes across the wall thickness.
• These findings hint at a modulation mechanism that adjusts the hoof wall properties, possibly by altering the volume fraction of specific IF components.
• This phenomenon, it’s suggested, counterbalances other functional, component-specific alignments in the hoof wall that would otherwise impact the modulus (measure of a substance’s resistance to being deformed) of certain regions adversely.