Peripheral loading and why its not ideal

The phrase "peripheral loading" was - as far as I know - coined by Robert Bowker and the first time I heard him say it was a lightbulb moment for me because it perfectly encapsulated how the shod hoof works and why it can cause problems.

Look at this image of someone trying to balance spinning plates - its hard enough, but its only possible if he has the point of support in the centre of the plate.   You won't find any pictures of people balancing plates using a point on the periphery because its not possible - putting weight on the periphery makes the whole thing unbalanced.

With that in mind, have a look at these 2 photos, which many of you will have seen before. Contrast the loading in the shod hoof and the barefoot hoof.   Just imagine how much more difficult it is for the peripherally-loaded shod hoof to have correct medio-lateral balance.   Even if the farrier gets it absolutely spot on the day the horse is shod, it's quite likely to be spinning out of balance by weeks 4, 5 and 6 of the shoeing cycle.

The reason I started thinking about how best to describe this was because of an interesting link which Wiola sent me when we were brainstorming :-)  In this clip, a farrier is describing the importance of correct hoofcare (skip the first 3 and a half minutes which are unedited and mostly feature sky and palm trees!).

http://www.usefnetwork.com/featured/GeorgeMorris2012/#ooid=5ib3A1MzrkQno6433FClbVKQUHTEa5J0,5pcHA1Mzq5P1pD-DpFLszE1BUCdIpxGw,90OG04MzorcE8vFWzOh8cTijAvOds_TX

This farrier is obviously tremendously committed and caring and is passionate about hooves.  I mean no criticism of him in this post and there is lots of good in what he says.

However, by minute 11 of the talk, he begins to get into hoof function.  He explains how  - alone of all animals (his words not mine) - the horse is the only one who loads the outer rim of the hoof, rather than the sole and centre of the foot.  But of course this is only possible in a shod horse, as he makes clear.

Interestingly, he doesn't consider whether the shoe is in fact changing how the horse's hoof functions.  Although he acknowledges that there are lots of hooved animals in the world, and many of them are domesticated, he confirms that none of them load their feet in the same way as a [shod] horse, without wondering how bizarre this is.

He's not oblivious to how unusual or difficult it is for the horse to load his whole bodyweight on the laminae  - in fact he marvels about how extraordinary this is, and how much stress the laminae are under, as they are bearing the whole weight of the horse. He goes on to describe how horses who have done fast work are often lame the next day if they have weak laminae because of the immense load and tearing the laminae are subjected to.  He has based his explanation of hoof function on standard farriery texts, which describe how the horse is capable of weightbearing via the laminae in this way.

But since even these texts acknowledge how tremendously unique and difficult it is, from a biomechanical point of view, for the horse to transfer weight through the laminae to the ground, surely there is a next logical step: to question whether the horse really IS an evolutionary anomaly, whether it really IS designed to shock absorb primarily through the hoof wall and whether the laminae really ARE designed to bear the whole weight of the horse?  After all its only when horses are shod that these assumptions are required - isn't there a danger we are making the biomechanics fit the shoes, rather than the other way around?

So looking at it logically and looking at the biomechanics of every other [unshod] hoofed animal, isn't it just possible that the shock-absorbing structures of the heels, frog/pad and digital cushion might be better suited to taking the weight of the horse, as they do in every other hoofed animal?  Leaving the laminae to do the protective job of hoof wall or fingernail, as they do in every other animal?  It also makes maintaining correct medio-lateral balance a whole lot easier...

Back to spinning plates...

As the saying goes (thanks to Sez for this!): "The wood is over there, by the trees..."