This is the second part of my recent blog post on bars, and whether or not they smear all over sole. To recap, Cheryl Henderson believes that the zona alba of the bar (i.e. the unpigmented inner wall) can outgrow its corium and lay over and smear all over sole. The evidence is the cadaver hoof that I talked about in the previous blog post. And I already explained why I have a different interpretation of the patterns observed. But the discussion is not complete without talking more in general about pigmentation of the hoof.
The hoof is nothing else than modified skin. The skin contains specialized cells (melanocytes) that produce melanin (or dark pigments). Black hooves, like skin, have cells that produce melanin, while white hooves don't produce melanin. It is a simple genetic factor that determines whether skin does or does not produce melanin.This is an over-simplification, but enough to understand the point I would like to make.
As many of us have seen with our own eyes, melanocytes in the skin can actually get damaged and loose their potential to produce melanin. Any sort of injury can cause this, or even just too much pressure. Examples are the brands that some horses carry, or the white spots many horses have on their withers due to an ill fitting saddle.
The same thing can also happen in the hoof. Areas of the hoof, who are under very high pressure can loose their ability to produce pigments, so that on a genetically black hoof, some areas can be white. In the hoof, the pressure is usually concentrated under the coffin bone. This is why we find in a lot of cases "white imprints" of coffin bones on an otherwise black sole. The first example below belongs to a mustang, who has a very worn down and very short hoof. This mustang must have traveled many many miles on hard ground.
This hoof belongs to a black (i.e. genetically melanin producing) horse. The wall is black and the coat is black. The sole should be black too, however, if we look closely, there is an area of white sole right throughout the front part of the hoof. This is exactly where the coffin bone is located, and where it descends upon weight bearing. I have circled the coffin bone imprint on the sole in red. The most likely explanation of this pattern is that pigment producing cells have been destroyed in this area of massive pressure. Though this effect has absolutely no effect to the horse, the hooves look totally healthy and fully functional, for that horse in its environment. The horse does not care if his or her sole is white or black. It just is a symptom of a cause, namely, in this case, a very hard working hoof.
The next example is my own mare, who is also black and also should have an entirely black sole.
She shows a very similar phenomenon to the mustang hoof, namely the imprint of the coffin bone on her sole, though much less pronounced, as an area of white. It is easy to see in the polished hoof from the snow. Before I started trimming myself, I never noticed this, but as soon as I did I was wondering about this. The position of the white would not change, or go away over the course of 4 years now. It just stayed there and it will never go away. This is because once the melanocytes are destroyed in a certain area, even if the excess pressure is now gone, the cells are destroyed for good. My mare's hoof will never ever return to a pure black sole.
Here is another case. This horse is severely overtrimmed (it has been lame for a long time), and one can clearly see the imprint of the coffin bone as missing pigmentation on otherwise pigmented hoof. This is another example where the concept of "bar smeared over sole" and instructions to remove it in my opinion will make this horse only worse, as there is no bar smeared anywhere, only lack of pigmentation on the sole. On the bright side, this hoof does not require any mapping, as the white pigmentation will exactly tell where the coffin bone is located.
Or in some cases, hooves can show white sole in areas around the frog, but otherwise black sole.
In the last case, the most likely scenario, that generated that pattern involved excess sole build-up around the frog that also exerted too much pressure and destroyed melanocytes forever, at some point in the past. This could have happened a long time ago, but the effect will be visible forever.
As I said above, pigmentation loss in the sole of the horses does not seem to have any effect. The only time it does is when people misunderstand this pigmentation pattern, and believe it is bar that needs to be dug out. Then very often, they will be surprised that a) they hit blood trying to remove that area of sole, and b) the white pigmentation is still there, even after years of trying to eliminate it.
Totally unrelated to what I would call "acquired pigmentation loss", there are also hooves that have stripes or spots of white on the sole due to the genetic patterning of the horse. These are common in Paint horses, or horses that have markings on their legs, such a white socks. My mare, for example, has a right hind foot that is half white and half black. She is totally black otherwise, with a tiny white star on her fore head. The sole on that right hind too is half white and half black. This is unrelated to pigmentation loss due to pressure, but represents a genetic patterning of the horse. Of course, acquired pigmentation loss and genetic patterning of the hoof could occur at the same time in one horse, so interpreting pigmentation patterns on hooves is often not so easy.
The hoof is nothing else than modified skin. The skin contains specialized cells (melanocytes) that produce melanin (or dark pigments). Black hooves, like skin, have cells that produce melanin, while white hooves don't produce melanin. It is a simple genetic factor that determines whether skin does or does not produce melanin.This is an over-simplification, but enough to understand the point I would like to make.
As many of us have seen with our own eyes, melanocytes in the skin can actually get damaged and loose their potential to produce melanin. Any sort of injury can cause this, or even just too much pressure. Examples are the brands that some horses carry, or the white spots many horses have on their withers due to an ill fitting saddle.
The same thing can also happen in the hoof. Areas of the hoof, who are under very high pressure can loose their ability to produce pigments, so that on a genetically black hoof, some areas can be white. In the hoof, the pressure is usually concentrated under the coffin bone. This is why we find in a lot of cases "white imprints" of coffin bones on an otherwise black sole. The first example below belongs to a mustang, who has a very worn down and very short hoof. This mustang must have traveled many many miles on hard ground.
This hoof belongs to a black (i.e. genetically melanin producing) horse. The wall is black and the coat is black. The sole should be black too, however, if we look closely, there is an area of white sole right throughout the front part of the hoof. This is exactly where the coffin bone is located, and where it descends upon weight bearing. I have circled the coffin bone imprint on the sole in red. The most likely explanation of this pattern is that pigment producing cells have been destroyed in this area of massive pressure. Though this effect has absolutely no effect to the horse, the hooves look totally healthy and fully functional, for that horse in its environment. The horse does not care if his or her sole is white or black. It just is a symptom of a cause, namely, in this case, a very hard working hoof.
The next example is my own mare, who is also black and also should have an entirely black sole.
Here is another case. This horse is severely overtrimmed (it has been lame for a long time), and one can clearly see the imprint of the coffin bone as missing pigmentation on otherwise pigmented hoof. This is another example where the concept of "bar smeared over sole" and instructions to remove it in my opinion will make this horse only worse, as there is no bar smeared anywhere, only lack of pigmentation on the sole. On the bright side, this hoof does not require any mapping, as the white pigmentation will exactly tell where the coffin bone is located.
Or in some cases, hooves can show white sole in areas around the frog, but otherwise black sole.
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| Picture by Torill Iversen |
In the last case, the most likely scenario, that generated that pattern involved excess sole build-up around the frog that also exerted too much pressure and destroyed melanocytes forever, at some point in the past. This could have happened a long time ago, but the effect will be visible forever.
As I said above, pigmentation loss in the sole of the horses does not seem to have any effect. The only time it does is when people misunderstand this pigmentation pattern, and believe it is bar that needs to be dug out. Then very often, they will be surprised that a) they hit blood trying to remove that area of sole, and b) the white pigmentation is still there, even after years of trying to eliminate it.
Totally unrelated to what I would call "acquired pigmentation loss", there are also hooves that have stripes or spots of white on the sole due to the genetic patterning of the horse. These are common in Paint horses, or horses that have markings on their legs, such a white socks. My mare, for example, has a right hind foot that is half white and half black. She is totally black otherwise, with a tiny white star on her fore head. The sole on that right hind too is half white and half black. This is unrelated to pigmentation loss due to pressure, but represents a genetic patterning of the horse. Of course, acquired pigmentation loss and genetic patterning of the hoof could occur at the same time in one horse, so interpreting pigmentation patterns on hooves is often not so easy.
Could you be so kind to mark my photo (the last) with my name? Torill Iversen. Or remove it since its my property and you didn't get permission to use it. If the readers is interested in the story behind my photo I'll provide it. But I do agee with you that horses can loose pigmentation in the sole area from pressure. When that happens it happens around the edge of the P3 leaving this halfmoon pattern you see in the first photos in this post. You can check up Natalija Alexandrova, she has written an article about it.
ReplyDeleteI saw Natalija's article on that. I was the one who brought this pattern to her attention. In the Academia Liberty forum, maybe 3 years ago. I'll add your name if you wish.
ReplyDeleteIn fact, since you seem interested in the whole story, this is it: I first formulated the question what the white half moon in the toe of my mare was towards James Welz on Hoofhelponline, around the end of 2011. He told me that it was a pattern of "coffin bone resting to much on sole". I then made that connection with the pigmentation loss due to injury and pressure and presented my theory to Natalija and the Academia Liberty for Feedback. This, I believe, is how she became aware of this and even used my analogy with the saddle spots.
ReplyDeleteVery clear post about the skin. We must maintain clear skin tone by taking preventive measures. Use proper sunscreen with SPF 50, use Hyaluronic Acid moisturizer for skin hydration, 24k gold serum to remove wrinkles and fine lines, best cream to remove dark spots, face creams for pigmentation. Lip Balm with SPF 30 with cocoa butter will smoothen the skin.
ReplyDelete