What are the signs of a healthy hoof?
The hoof is believed to be strongest when it has a stable moisture content of 25%. Hooves in this state do not readily absorb excess water and are in fact strong, durable and able to withstand the stresses of work and shoeing. Hoof horn is constructed of two types of keratin molecules – spring-like spiral structures and more rigid zig-zag structures (see diagram opposite).
Each structure is formed with the assistance of hydrogen bonds within or between the keratin molecules. The two different structures are bound to each other by disulphide links. These spring like structures are able to coil to absorb concussion and shock, whilst the zig-zig structures are rigid and act as dampers similar to the shock absorbers in a car.
What happens if the hoof becomes water-logged?
Water is naturally present and evenly distributed throughout the hoof. There are two ways water is stored in the hoof; either free moving or bound, trapped water. When the hoof is exposed to excessive amounts of water, moisture molecules flood the hoof structures.
The hoof swells to accommodate the water, which then weakens the hydrogen bonds that form the springlike and zig-zag structures. The weakened hydrogen bonds cause the shock absorbing springs to become stretched, elongated and unable to re-coil.
The hoof structure is therefore changed and ceases to act as a shock absorber. Hooves in this state may look surprisingly healthy as any minor cracks tend to disappear due to horn expansion. However, the horn is weakened and prone to being soft and crumbly. It is not surprising therefore that shoes are easily lost, especially in heavy-going.
How does the hoof become dry and damaged?
On a hot day if a water-logged hoof dries out too quickly, irreversible damage can occur to the molecular structure. Rapid removal of moisture from the hoof does not give the spiral and zig-zag structures enough time to re-align. Hydrogen bonds stretch, break and are unable to reattach and realign, so the structure collapses.
This damage can cause the horn to become dry, brittle and often exhibit cracking. Always remember, it is this rapid removal of moisture that causes the damage.