What happens when hoof wall "wears away"...

Surely the commonest - and most misunderstood - reason given for horses "needing" shoes is the perceived "protection" that shoes provide. One of the flaws in last week's H&H article was a vet's assertion that "working on roads can wear away the hoof wall" which, according to the author, leads to pain and means that only horses who work on soft surfaces can cope unshod.

The Worshipful Company of Farriers also cites this in support of shoes. When working an unshod horse, according to its website, "you can have problems with grip, excessive wear and damage to the hoof capsule." There is apparently a risk that unshod hooves "may wear a lot quicker than the hoof wall growth can replace itself, thus making potentially sore feet with lack of performance".

Despite the slightly bizarre grammar, the point is clear: both the vet and the WCF have assumed that horses depend on their hoof wall to support the limb and that therefore once a horse has worn away its hoof wall the hooves become sore.  

If you shoe horses, this is a perfectly logical assumption because - after all - a shoe sits round the rim of the hoof. It not only effectively prevents any wear to the hoof wall but ensures that the horse is loading most of its weight onto the hoof wall; in a shoe the sole and frog have very limited load-bearing.

If you are used to a foot loading like this (what Bowker calls "peripheral loading") then you will assume that even out of a shoe it should load the same way - round the edge of the hoof onto the hoof wall.

And, if you simply take a shoe off, then many horses will indeed load this way for a short time and if they are kept on soft surfaces. The horse above was peripherally loading out of shoes and walking on its long hoof wall (there was at least an inch of hoof wall proud of the sole - the sole shot of the same hoof is below). 

Once the level of wear exceeds the level of growth or the horse works on hard surfaces, the hoof wall length will reduce till the horse is no longer walking on a rim but (we hope!) landing heel first and engaging frog, heels and sole.

This is the same foot a short time later, after turn-out on our tracks but no trimming. 

In a really hard-working barefoot horse (like the self-trimming example below) the hoof wall will be almost completely worn away at ground level and there certainly won't be a rim of hoof wall for the horse to load. The frog, heels and sole will be the main areas of loading, not the periphery. 

These - two of my favourite photos - provide a really clear illustration of how differently shod and bare feet load on the same surface. 

The shod hooves load only the periphery and there is no contact with frog or sole...

The bare hoof loads frog and sole and though the hoof wall makes contact with the ground its not bearing the majority of the load.  For me, its clear that the bare hoof is functioning better - but why do I think this?

Not just because - in a healthy hoof - a "lack" of hoof wall won't impair soundness but more importantly because hoof wall isn't designed to support the whole weight of the horse. 

Think about it - hard hoof wall evolved as a protective shell. Anatomically, its a toenail - as this illustration makes clear...

...and horses have hoof wall for the same reason that we have toenails - to protect internal structures from damage. But we don't walk on our toenails and neither do hoofed animals - its the soles of the feet (even though they are apparently softer!) which are designed for that. 

Walking like this - for us or our horses - allows for proprioception, shock absorption and balancing in a way which would be impossible if we were on hard, unyielding nails or hoof wall.

In fact any walker will tell you that if you go hiking with toenails which are too long, so that they come into contact with the end of your boot as you walk downhill, it quickly becomes painful because toenails (like hoof wall) aren't designed to take significant load.

Loading the soles (and in horses' case the frogs too) also means that the surface which is in contact with the ground (the epidermal layer) is capable of growing and thickening in response to stimulus. Another quality that hoof wall doesn't have.

So the next time someone tells you that horses need shoes so their hoof wall doesn't wear away, ask them whether they walk on their toenails or their soles...