Viscoelastic properties of the equine hoof wall.

This study researched the hardness and flexibility (viscoelastic properties) of a horse’s hoof wall at both macro and microscopic levels, and under both dry and hydrated conditions. The aim was to improve the understanding of how the hoof wall absorbs impact, with consequences for design in fields such as engineering and sport.

Research Methodologies

The researchers used two techniques to measure the hoof’s viscoelastic properties:

• The first one, dynamic mechanical analysis (DMA), is conventional and operates at a macro scale, approximately 5 mm.
• The other technique is a nano version of DMA that works on a much smaller scale of about 1 micrometer (μm).

Through these methods, they evaluated the magnitude changes of complex moduli – indicators of how a material reacts to stress – for both fully hydrated and dry (ambient) hoof wall conditions.

Findings

The researchers’ discoveries included:

• The dry hoof’s storage modulus, or its ability to store and release energy, was about 400 MPa (megapascals) under conventional methods, but this dropped to 250 MPa when the hoof was fully hydrated.
• The loss tangent, or measure of a material’s damping capability, decreased for both the dry and hydrated hooves across the frequency range of 1 to 10 Hz. This means that as stress was applied more frequently, less energy was lost through deformation or damping as heat.
• The researchers also noted little to no changes in the frequency (beyond 10 Hz) for nano-DMA tests performed up to 200 Hz.
• In terms of sub-structures within the hoof, the team found that the areas made up of tubes were more sensitive to hydration than the areas between tubes. The storage modulus remained stable across these areas.
• Loss tangent and effective stiffness were higher in indentations across both hydration levels.

Implications and Significance

The study’s findings shape knowledge about the structure and behaviour of the horse’s hoof wall, which evolved to handle high impact from galloping. This is significant as it provides useful data for simulating and testing different impact speeds. The results also show that hoof wall behavior aligns with that of other biological materials and polymers, especially when hydrated.

The research findings could lead to better design and manufacture of bio-inspired materials and structures that must withstand heavy impacts. Understanding the hoof’s hydration sensitivity could also contribute to related fields, such as equine health and veterinary science.