Frusto-conical means of a Frustum, of a Cone. A Frustum is a section of a solid. Like a slice of cake taken out of the middle of a cylinder, square or cone. So picture a cone and slice the top off to give yourself a hoof-shaped section. Tada: Frusto-Conical!
Now would be a good time to again refer to the fact that the hoof is not a tube. If your hoof is the same circumference at the top as it is at the bottom, something is wrong.
A horse’s hoof is like a flashlight beam. The further away from the start, the wider the path of the beam gets. Carrying on with the concept of a flashlight, if you pointed it STRAIGHT DOWN, you would get a perfect circle.
But horse’s hoofs don’t grow straight down, do they? They grow FORWARD. Hold a flashlight forward, what do you see the beam of light do? At the end it turns into an oval. This is not me insisting on what shape a hoof is, this is just logic and the way geometry happens to work.
The more upright that foot is, the more you will get the appearance of a circle. The more it is slanted out, the more of an oval you will get. Tube toes that are upright will look like circles. Long, platypus toes will look like ovals.
While these are exaggerated images, the point is easy to see. Like Goldie Locks would say, “This foot is too round and upright, this foot is too sloped and oval.” Somewhere in the middle is a happy angle for the hoof, one that ends up not too circular and not too ovular. Most horses will have a *slightly* oval hoof and not be truly “round”, as the flashlight angle never lies.
We went over one of the frog’s functions as being the elastic that lets the hoof spread. This hoof is a shock-absorbing device. What happens when the hoof is overly upright or overly sloped?
Upright and short, like a brush, leads to very firm and abrupt shock. If you’ve taken a short bristled brush and hit it against a surface dead on, the bristles are rigid and shocking.
If you’ve taken a longer bristled brush that had angled bristles and tapped it the same way, it would be less shocking. The bristles splay to the sides a bit more and aren’t as rigid.
Here is an excellent before and after showing an upright hoof that was trimmed and what happens to those solar measurements in the process:
In the upright-appearing hoof we have a very round solar appearance.
Now, post-trim, the hoof appears to be more angled. This isn’t an exercise in “what angle should this be” as we weren’t there to read the hoof in person and make that call. But on Black Pony’s first trim, we can visually assess that his angle is now less upright. When we see his solar view, we can see it is slightly more oval shaped and less round appearing than it was before.
So we can see too upright and too sloping and get an idea of how each would be a disservice to a horse. The upright has too much firmness and jarring absorption. The low slung has no support and lacks shock absorption.
Remember how we saw that the bars were an extension of the hoofwall? Same material, same support and durability?
Look at these bars:
The hoofwall has been trimmed or worn down relatively evenly, then you get to the bars. They are TALL! Like the long brush bristles we saw, we see that right bar just flopping over. Where the hoofwall turns into the bar is the “heel” and thus we know we have high heels in this horse. What would make me guess that? This hoof is also wider than it is long. Shocker. This is a flashlight held more upright than sloped. You are going to get a circular-shaped foot. If it’s more upright than long, you guessed it: you gotta have heels to make it high!
Just like walking in heels, you no longer have the flex of your foot as your first point of absorption. Like the “classic” image we get of a woman sauntering in heels, we can imagine horses with blocky, upright feet also moving in the hips. Their feet wouldn’t be absorbing shock, but their hips and shoulders would be. Their feet would be ouchy (just like me in heels after about 10 minutes) and so they would quickly lift their feet (hot potato! hot potato!) from left to right, alternating pressure.
When I had Friesians and Gypsies and worked with people with Shires and Clydesdales I saw that they were prone to having high heels and rounder, more upright feet with how they were trimmed. They had “flashy” gaits to match. It was often hard to see what was happening under all that feather. Out of sight, out of mind was an issue for me.
Then should we err on the side of long and sloping? To be blunt, it would end up feeling a bit like a lifted toenail in a runner.
Remember, we have Velcro holding the bone to the hoofwall and we have a knitting of the sole to the hoofwall by means of the “white line” (which is actually more yellow-cream looking). Check out that “seam” in close up. You can SEE the laminae stretching to hold together.
When that toe gets “too long” it starts to lift like a runner’s toenail. Look at how far it’s stretched in attempting to hold the sole to the hoofwall in the image below. You can clearly see how that toe is “too long” for that horse.
Ouch! And with a toenail that hurts that bad, you can guess that the horse will have a choppier gait. He’s going to land heel first and when he rolls to the toe he’s going to halt his breakover and pick up his foot earlier than his normal gait would want, as he doesn’t want to keep “lifting his toenail”. Just like a runner, we could trim his nails and ease up that pressure. There are several breeds of horses that people leave with long toes. Their avoidance of that toe pressure causes them to snap their legs up instead of breakover. This is seen as flashy and desirable in certain breeds. Despite the appearance of all sorts of shoeing devices they put on them (that will visually cause you to do a double-take on where the hoof ends and the device begins) look at the length and slope of that toe:
A Tennessee Walker
What will end up happening is the heel will take more and more of the support. A horse normally has a heel and toe to land on and push off from. He has two points carrying 50% of the work each. Like a front and back pillar. With the toe out of commission, he has to cover 100% of the work with his heel. Not surprisingly, the heel moves forward to be a better support point. It now is handling the weight “centrally”.
And like a runner’s lifted toenail, the front of the hoofwall, normally velcroed to the Coffin Bone, will start to pull away. You can see, in the x-ray below, there can start to be a gapping wedge between where the coffin bone is at the top end, and where it is at the bottom end. It un-velcros.
Now, before the pitch-forks come out, I would like to say I am showing these bottom two as visual examples of a laminar wedge as caused by too long a toe and no farrier maintenance. I know they can also be caused through laminitis or founder.
Stay tuned. Our next stop is “Bulb Butt: Do these shoes make my bulbs look big?”