Something that is quite common to see when examining and trimming hooves in the summer and cold dry winter times is a buildup of the sole that may make the hoof look flat on the bottom or just rough and cracked. When this gets further into the wet season you may find that pieces of sole fall off at once almost like a sheet of paper. The roughness and cracks can lead to bits and pieces breaking off in chunks, which is completely normal. In the case of larger pieces that peel off, it may seem concerning as it looks like the sole is going to fall right off the hoof, but it’s normal too. The only exception is in the case of a subsolar abscess, but that’s different and for another article.
The first example we’ll take a look at is a flat hoof bottom in the summer:
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False sole buildup generally occurs in the summer time, but can occur at any time of the year really when the ground is dry and hard. The way the hoof works is that it is constantly putting out keratin cells both out to the hoof wall and down to the sole. If the conditions are right, the hoof will wear down as fast as it builds up. In some conditions though, the hoof wall gets long and needs a trim, and again in others, the sole will continue to build up instead of exfoliate naturally. Hot and dry weather tends to promote this most and then the flaking off and exfoliating happens when it gets wet and softens up the dead, and now unneeded, sole buildup.
The sole of the hoof is in place to support the bony structure of the horse and somewhat protect the corium and all internals of the hoof. It’s quite hard and packed down, which protects when stepping on rocks and other rough surfaces. While it is quite hard, it’s not as hard as the outer wall and is completely useless for protection for sharp objects like nails, which can get through at most angles. The cells that head down that way can grow in quite hard and pack down very well to start to fill in all spaces to get rid of that concavity that we are used to seeing when examining hooves. While it’s possible to just carve it back out, when hard enough it will seriously dull your tools, which is primarily the knife in this case. The question is, should it be done and is it worth it?
For some it’s the rule to carve it out and put the concavity back in the hoof. This has both pros and cons but most importantly without having a very watchful eye and hand doing it, you can thin out the healthy sole accidentally and in turn easily cause lameness.
If we think about the necessity of removing the false sole, we would have to consider the rest of the hoof and horse. The first question to ask is if the horse is moving poorly or limping on one foot or not. With sole buildup it’s very easy to grow past the bars and long bars can cause a horse to be uncomfortable or even in pain. This can also compromise the very important heel buttress area. So while the false sole itself isn’t the problem, the long bars are. This also hides the true length of the hoof wall, which leads to heels and bars getting long and can put a horse up at a higher angle than they should be.
The best option obviously is to have the horse wear their own feet down, but a lot domesticated horses do not have this option due to lack of movement. Even on bad/rough footing like crusher dust, or an equivalent of cement which seemingly will wear down a horse’s hoof, you will likely still need to get a trim done just due to the fact that the horse doesn’t move enough. This should be a clue as if the hoof wall isn’t wearing down enough to not need a trim, what should make us think that the sole is?
The one case where you never want to remove false sole to create concavity is in a horse that has thin soles. So if we start to think about removing it, we need to figure out how much healthy sole the horse has in the first place. If less than 1/4″ or so, then it’s imperative to leave that false sole in place for protection. A very important item to consider. If you see excessive flaring of the hoof, then the soles are probably thin, leaving the false sole in place may be the only protection the horse has between the ground and the internal structure. Here’s a picture of one that desperately needs the false sole that has grown in:
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If the flaky and chalky sole was removed from the horse above, it would be dead lame as there wouldn’t be any protection left. This is an extreme case though.
The case where you’d like to remove that sole is if the horse is having trouble walking on it due to being too thick. This is where measuring the collateral groove depth in comparison to the lowest point of the hoof (which may be and should be the hoof wall), is an important tool for the decision. If you have more than enough sole depth, over 5/8″ or so, then you could probably start exfoliating a bit to see if a difference can be made for the comfort of the horse. Starting at the edge of the frog and working down to the shiny and healthy surface of live sole. No further. Then slowly work outwards to the edge. The amount to remove should be less and less as you go outwards and in time you should be able to find all of the live sole, which will allow you to find your true bar and hoof wall length.
Here is an example of a hoof with exfoliating sole that it doesn’t need anymore. Check the red circle area and you can see how there is a layer of missing sole and the portion towards the toe is lifting:
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Here’s a different angle:
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and one more:
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While it’s mostly just fine to leave this sole, as it’s already exfoliating naturally, it’s also fine to help it along as it’s easy to just peel off with your fingers. This essentially means that the sole underneath is ready to do it’s job. Sometimes if you take false sole off a bit early, in the case of abscesses, the sole underneath is not packed down hard enough and is more susceptible to injury and puncture. This hoof is more than healthy enough to lose this layer and this is what it looks like as you start:
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The edge of this cut shows there is the real layer of sole under the false layer. As the layer thickness is uniform across the sole, it’s even more proof that it’s a false sole and likely from the winter, or even summer.
The bottom line though is that false sole is generally just fine to have. If the footing was rough enough, it will wear it out just fine and exfoliate naturally. If not, the horse may just plain need that extra protection against the elements. A flat sole does not always mean a weak hoof and in fact can just mean it has extra armor against what the horse may come up against. The measurement of a thin/weak sole is by thickness, which is measured by depth of the collateral grooves from healthy sole to hoof wall. Not so much by judging concavity as there may be just a buildup next to the frog rather than not enough on the edges.