the growth direction of bar

This is the third part of the post on bars, whether or not they can and do smear all over sole and encircle the frog.

Shown in the picture below is another cadaver hoof that was exposed to the dermestid beetles. The only difference between this hoof and the one in the first post is that this time the hoof is pigmented and not white.

On the left side of the picture I show the corium of a hoof. The black arrow points to the bar corium, i.e. the cells from which the bar grows. One can clearly see the directions of the tubules. They face outwards, in the direction of the quarters of the hoof. The blue lines therefor project where the bar will be growing towards. On the right side of the picture, we can see that this is exactly what the bar wall has done, grow out towards the quarter of the hoof. The bars of this hoof have probably not been trimmed in a while. At least the one on the right side of the hoof. Often times, the consequence of a bar that grows high towards the quarters is a flare on the quarter wall. And this is what seems to have happened to this hoof too. The right side of this hoof in the picture seems much more flared than the left. Most likely the horse, due to its conformation, wore the left side well by itself, and the right side not so well. 

In the next slide I have placed the pigmented and unpigmented cadaver hoof on the same slide.

To recall, Cheryl Henderson is using the left cadaver hoof as proof that bar can smear around the frog (the parts that is pointed to by the red arrows). However, as one can see on the pigmented hoof, the same material that she claims is smeared inner bar wall (zona alba) on the white hoof is pigmented on the black hoof. The zona alba however is white on both white and black hooves and thus on the black hoof, this material that finds itself left over by the beetles and located next to the frog is not zona alba, but very likely ordinary (calloused) pigmented sole. At least the color of it does not provide any evidence for it being bar. If it would be bar, it would now need to be the outer pigmented wall of the bar that smears around the frog.

We can also see again, as in the pigmented hoof, the unpigmented hoof has one bar that wears down by itself nicely (right side of hoof) and one that obviously was trimmed recently (left side of picture) and had grown quite high up towards the quarters.


Taken together this post the patterns observed suggest that the bar does not grow forward on the hoof (i.e. towards the tip of the frog) but outwards, in the direction of the bar corium tubules, towards the quarters and not the tip of the frog.

pigmentation loss in sole

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.

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.

flesh eating beetles and "bar smear"

This blog entry has long been in the making. I started writing it in April 2014. The topic of this post will be bars, and whether or not they can “circle around the frog”, “smear in the sole” or “overlay the sole in a thin veil”.

Bars migrating or smearing or pushing up in the capsule is a central theme in the ABC hoof print trim. According to the inventor of the ABC trim, Cheryl Henderson, many pathologies are attributed to bars having migrated to places they should not be, or getting imbedded in sole. Often times, painting a picture where bars overlay the sole and crush new sole tubules underneath lead beginner trimmers (including me in early 2011) to dig out supposed bar material, in search for some sole underneath, but instead finding themselves having “quicked” (i.e. hit blood) their horses (thankfully excluding me!).

I personally started questioning this idea, that bar smears or migrates when I was removing it over the course of 6 months to one year, only to find, that my horses a) became extremely sensitive on their soles and b) the supposed “bars” growing back every time exactly the same way as I found them 4-6 weeks prior.  So I concluded that something must not be correct with this theory.

Cheryl Henderson believes that her own research has proven that bar (or better the “zona alba” of the bar, i.e. the inner unpigmented wall of the bar) can migrate and circle around the frog. However, what people without any formal research training may not realize, this research is merely an observation combined with a hypothesis and not a proof whatsoever.

The scientific process usually has several steps:

1)    Most research starts out with an observation.

2)    Next, one proposes a mechanism for that observation.

3)    Third, one proves that this mechanism is indeed able to generate the observation. The proof is NOT the observation itself, or otherwise it would be an entirely circular argument.

4)    One states exceptions to the rule, or how significant the observation is. For example, of all cadaver hooves that were analyzed, the patterns of bar circling/embedding around the frog has only ever been observed on white hooves. Not on black hooves. (Note: on white hooves bar and sole are basically indistinguishable, whereas on black hooves white bar circling around or embedding into sole should easily be distinguished from black sole).

5)    One submits the research to a scientific peer-review process stating truthfully all observations that have been obtained, and not only the ones that fit the mechanism proposed by the author

6)    The scientific community then decides if a study is worthwhile publishing provided all rules of good scientific practice have been followed.

In the particular case of Cheryl Henderson’s beetle cadaver study, if it would ever have reached step 5), the reviewers should have severely questioned the results based on point 4). It is HIGHLY unlikely that a mechanism of bar circling around the frog should be limited to white hooves only.

So here is now a more detailed description of the research. It is pretty simple, but I admit, very cool and also very appealing to people who do not know any better: she throws a hoof in a container with dermestid beetles. These beetles are used by taxidermists (and crazy biologists at times) to clean bones from flesh. An example of one hoof after being exposed to the beetles is shown below. This picture has been circling Facebook for years now:

What remains of the hoof after the beetles have spent some time with it is the wall, the bars, and some material that is attached to the bars but have a flat appearance encircling the frog (which of course is not there anymore, as the bugs most likely ate that one first, as it is about the softest material on the whole hoof). Her conclusion is that the latter, since it is connected to the bar, must have grown from the bar, and therefore represents bar. Then she goes on explaining that very many horses have bar circling around the frog and this causes them major damage.

My criticism would be that there is no proper scientific protocol being followed here. It is just an observation, followed by a hypothesis. And that is fair enough. This is the first step in all research. The problem lies in the fact that Cheryl considers this observation as proof. It is a good observation, but the conclusions and implications she insists it is showing do not exist. There is also no cautioning that there could be other explanations for the patterns observed, which, in science, until something is really proven several times independently, is almost always the case. Nor any mechanism that would explain how bar can so far outgrow its corium.

This is a cadaver hoof. I need to point out that this is NOT the same hoof as pictured above. Cheryl Henderson does not provide any pictures of the hoof depicted above before the beetles started to work on it. But the hoof below has the typical "bars circling around the frog" issue, that Cheryl is so particular about. I have circled the supposed "bar" in black.

This is the other side of that same hoof with the coffin bone sitting in the hoof capsule, but the navicular bone missing.

The blue arrows point to the true end of the bar, where the lamellae of the white line end. What is forward of the end of the bar are straight horn tubules, that look a lot like the ones from the hoof wall. They just somehow look different than normal sole tubules, somehow stronger and thicker. Yet, in my opinion, this is not bar that "smeared" or "migrated", but sole, maybe of some slightly different anatomy as sole further out on the hoof, i.e. not right next to the frog and bar. After all, this sole finds itself at a “junction” the junction between frog and sole and bar. It has to connect the bars with the sole and the frog. It must be a rather difficult task and one of massive importance. Junctions usually are weak points, so it would make total sense if that junction would be somehow re-enforced by having some stronger sole tubules. 

I am not saying that my interpretation is necessarily correct. It is just as much of a hypothesis as Cheryl’s interpretation is one, that this material is inner bar wall smeared out from the back of the hoof. Future research would need to look in the detailed anatomy of hooves and in particular that junction between bar, sole and frog on many hooves, black, white, from lots of different living environments etc.

Now, this bar/sole/frog junction horn is exactly the horn that the bugs don't like eating.

 As I said above, in my opinion, the fact that the beetles don't like eating this structure does not prove it is bar. It is attached to bar, but this must not mean that is indeed bar. It is more likely that the sole near the bar-sole-frog junction is anatomically somewhat different. And this in turn would mean that the concept of trying to dig out bar around the frog is misleading. Yes, this cadaver hoof has some accumulation of excess material around the frog, I don't think anybody denies that, but it does not need to be dug out in search for sole "underneath". It simply needs to be smoothed off to the level of exfoliated sole around it, and that's it.

Now comes my evidence (still no proof!), that the material that circles around the frog is not bar, but compressed sole callus, that, on white hooves, can be difficult to distinguish from bar.  

Here is one of my geldings hooves from April 14^th of this year, when I started to work on this blog post. Short background on him is on top of the slide. If I would have approached Cheryl for help with this hoof (which I did 3.5 years ago) she would have told me to lower his heels, his bars and remove the material that I have marked in red in the following slide, claiming it would be bar that smeared out and overlaying the sole, crushing it underneath. She would have told me to take sliver after sliver and inspect it under the microscope so that I would know if it is bar or sole (but no information is given that this is even possible to distinguish under the microscope). It is a white hoof, of course, so bar and sole are hard to distinguish (to the untrained eye, for me it is simple now, as I know those hooves in and out). 

This is the area (circled in red) that I would have been told to remove, representing bar smear: 

 I have trimmed my horse for more than 3.5 years now, in a rather strict 4 week schedule. For the last year or so I have help by an AANHCP, who checks on my work periodically.  I know with 100% certainty that this material is not bar. I have defined the bars 100ds of times, all three layers of it, pigmented and unpigmented wall and white line. If one looks carefully one can see the white line in the bars straight and not laid over.

 In this slide I have marked the rough position of the coffin bone. It is quite clear in my mind that this red line tracks pretty well the coffin bone above.

And again here, in comparison to the material that the bugs don't like eating.

To me, all the evidence taken together points to a model where sole around the frog can take on various consistencies, callous and become really hard and sometimes look shiny and slick, so that beetles abstain from eating it, at least as long as they have anything else to eat. This is because the coffin bone exerts so much pressure, and for my horses, who live on a sand dune, the sand (or snow) packs in their hooves and creates a lot of counter pressure. The sole adapts to those pressures and callouses quickly and massively to provide the hoof with adequate protection. Does it look necessarily pretty and beautiful, like the mustang feet? No! Absolutely not, but these feet could master ice and snow without one slip and one ouch and that is what counts. Mustangs don't spend 3 months on 3 feet of snow. At least not the ones we take as models these days (the Australian brumbies or the Great Basin mustangs). Hooves do look different in every single environment, and that makes them so special, their adaptability.
 

In my mind, there is undoubtedly need for more research to study the different appearances that sole can take on in different environments, and also the anatomy of that bar-sole-frog junction. Linda Cowles has made a nice effort with respect to sole appearances. I have referred to her blog before:

http://mollyshoofjourney.blogspot.com/2014/08/the-different-appearances-of-sole-very.html

Clearly, noone has all the answers yet, and we all have to stay open minded and try and learn what it is the horse tries to tell us.