How To Stimulate Equine Hoof Growth

This video examines how hoof and sole is grown at a cellular and molecular level whilst anatomically showing how to increase hoof growth. It was presented at the University of Queensland in Sep 23

Video Transcript

Hi everyone, welcome to the first presentation from NE, the Dietary Shed. We look forward to more presentations of some of our interesting clinical cases in the coming months.

Why look at hoof microanatomy? Unfortunately, around 67% of lameness issues arise from hoof pathology of some form. Many hoof issues can be extremely painful and may even pose serious welfare or life-threatening risks. The key to managing virtually all cases requiring remedial shoeing is to increase hoof and sole growth rates. Growing the hoof wall in acute traumatic circumstances, such as this case, is critical from a welfare perspective and for reducing the time needed to return to work. Whether it's an acute or chronic rotational laminitis condition, incremental wall and sole growth will help protect P3, enabling an earlier response to remedial shoeing. In a Type 4 P3 fracture, like this one, accelerated sole and wall growth is essential for support and fracture resolution.

In the case of a bone sequestrum resulting from a penetrating injury, sole and hoof growth were critical in management, as was the regenerative capacity post-infection. Regrowing the sole as quickly as possible was vital in this case. Hoof capsule cracks are a classic example. Whether it’s a dorsal wall crack or a quarter crack like this one, they can be career-ending unless managed correctly. Accelerated hoof wall growth not only grows cracks out faster but also increases available wall mass, giving farriers more to work with and enabling quicker recovery post-osteomyelitis or post-operative cases like this, where there was extreme loss of P3.

This particular case involved a nodular fracture with clear resolution in just four and a half months. The horse was sound and back to work well inside the globally recognized expected healing timeframes. Elevated hoof wall growth rates greatly assisted in the outcome.

Increasing hoof and sole growth is inherently linked to successful remedial shoeing outcomes and, ultimately, improves horse welfare. Let’s dive into some anatomy to understand how the hoof wall, sole, and frog are produced.

Here we have a post-mortem specimen with the hoof capsule removed, where we can immediately identify fine velvet-like projections running all over the sole and frog. These are the papillae of the sole and frog, which, along with the coronary papillae, are structures that produce the keratinized hoof capsule. This diagrammatic representation of a cross-section of the hoof wall shows the coronary and lamellar papillae, which are responsible for producing the hoof wall. The hoof wall is only produced at the coronary band and slides down along the secondary germinal epidermal lamellae of the hoof.

Now, we could start talking about laminitis, but you’ll have to wait for one of our next lectures. Just to reiterate, the hoof wall is produced at the coronary band and slides down the lamellae. No wall is produced by the lamellae themselves.

Here, we have a magnified view of the coronary papillae and the sensitive lamellae, along with the coronary groove, which has holes that serve as the origin of the tubules. You can see how easily this structure can be bruised or damaged and how complex it is to manage simple hoof abscesses.

Now we ask: Why papillae? Why not a sheet of keratin laid down from a nail bed like a human fingernail? The papillae produce a keratin structure, using almost the same cellular building blocks as a human fingernail, but designed to withstand the weight, torsion, and impact required of a horse at a gallop—around 5,000 to 6,000 pounds per square inch. To put this in context, that’s nearly double the bite force of a saltwater crocodile. Suddenly, the papillae mechanism becomes even more intriguing and makes a lot of sense.

Essentially, the papillae are concentric cones of decreasing radius, separated by flatter areas of basement membrane, which produce the inter-tubular matrix. This highly oversimplified model shows how keratin is produced from the basement membrane, progressively creating mature keratinized hoof tissue.

This is a different author’s diagrammatic version of the multi-layered tubules and the inter-tubular matrix, which acts as flexible glue holding the tubules together. Recent research shows that each layer of keratin actually spirals in the opposite direction, further enhancing torsional strength. Here’s an incredible electron microscope picture of an actual tubule, showing compound cylindrical layers surrounding the inter-tubular matrix.

Engineers have copied and extrapolated this compound layered cylindrical concept in the design of rocket motors, submarine hulls, pressure vessels, aerospace vehicles, and power drive shafts.

This is a cross-sectional view from the outer hoof wall to the inner wall, with an electron microscopy overlay. We can see the differing tubule density between the outer and inner walls, which aids in the viscoelastic properties of the hoof capsule.

We’ve established that the hoof wall is a keratin-based compound, multi-layer tubular structure, bound by inter-tubular keratin matrix. What does a keratin molecule look like? How is it structured, and how does it function? The $64 million question is: How do we increase keratinocyte replication and healthy keratin production, thereby improving hoof wall strength?

Most keratin supplements are made from ground-up cattle or sheep hooves. The problem is that horses cannot absorb keratin or collagen in their natural form—they are complex polypeptides that need to be broken down to be absorbed. Here’s a diagrammatic representation of the keratin polypeptide double helix and the three types of bonds that hold the chains together: hydrogen bonds, ionic bonds, and disulphide bridges. The strongest of these is the disulphide bridge, which binds two cysteine molecules.

There are four primary amino acids in the keratin polypeptide. Cysteine, the only non-essential amino acid in keratin, has a particular significance due to its unique sulphur functional group. Arginine, lysine, and methionine are essential amino acids that cannot be synthesized by the horse fast enough to meet demand, so they must come from the diet. Without these four amino acids, keratin cannot be formed.

This structural formula diagram shows the disulphide bridge joining two sulphur residues, which gives the hoof wall mechanical stability and tensile strength. This bond is one of the most powerful naturally occurring bonds in nature, and sufficient cysteine must be fed to ensure keratin formation.

The Canadian Veterinary Research Journal published an interesting paper describing the factors that affect hoof quality, including nutrition, hydration, genetics, and environmental factors.

In conclusion, once we reverse-engineered the hoof wall to a molecular level, we formulated a supplement that included all the necessary building blocks for hoof growth. Initial trials were performed in Victoria, reviewed by independent equine veterinary radiologists. Results showed remarkable increases in hoof growth rates, helping with bone repair and overall hoof health.