Golden standard or total misunderstanding?
They say that if you draw a line through the lower three skeletal bones in a horse leg, the line must be straight, and the bones must be aligned. They also say that if this is not the case, you are supposed to correct this by changing the height of the heels.
Toe axis, broken or not, is a purely theoretical concept. They say that the lowest three phalangs (P1, P2, P3) in the horses leg are supposed to be alined (as the red line in the picture below) or the horse is suffering from a broken toe axis. There are multiple problems with this reasoning. As you can see in the picture above there is no standard or fixed angle on the lower three phalangs when the horse is moving. It is alldepending on the loading of the hoof. Yes, I’ve heard that you are supposed to check the toe axis when the horse is standing still, in balance, on a flat surface. But why when standing still on a flat surface when stresses and strains are the smalest? Even if you would have your horse standing still on a flat surface the toe axis will change as soon as he is looking to the side. And how do you check the angles of the skelletal bones when the only thing you can see is fur, and a hoof capsule that is only loosly connected to the coffin bone (yellow line). These are, however, just details because the main argument against the toe axis is that there is no force going in the direction of the theoretical toe axis, ever, which makes the complete reasoning about toe axis completely irrelevant.
Let me prove that to you:
If there was a force following the red line, it would also follow the wooden plank that the weight in this video is placed on, and if that was the case the trolley would roll to the left by itself, but it doesn’t.
The reason for this is that according to Newton’s Law of Universal Gravitation is gravitation defined as “a force that works in a straight line between the center of two objects”, which in our case is between the center of the weight and the center of the Earth., i.e. straight down.
The explanation to why this trolley isn’t rolling to the left by itself is because there is no force pushing it in that direction. The only force that is active is the gravitational force working in a straight line between the center of the weight and the center of the Earth, which doesn’t cause the trolley to move.
When we add an artificial force in the direction of the wooden plank the weight is resting on, the trolley directly rolls to the left.
The yellow lines are what you can see: fur and hoof capsule.
The blue lines are the outside of the skeletal bones (which would be closest to what you can see from the outside) but they are not parallel to the yellow lines and you can’t see them from outside.
The red lines, that are the only thing that could have any relevance, are still just lines since there is no forces going in that direction.
The force created by the horse’s weight and gravity that is pushing the hooves to the ground is always aimed straight down regardless of the angles of the hoof capsule, the fur, and the skeletal bones. The skeletal bones are to be considered building block kept together by ligaments and muscles but the force transferring the weight from the bulk of the horse to the ground is always angled straight towards the center of the Earth (black arrows).
Q. Why does a car that is parked on a road going uphill roll backwards when you loosen the handbrake?A. Gravity caused by the weight of the car will pull the center of the wheel towards the center of the Earth. This line will touch the outer surface of the tire behind the center of the contact area between the tire and the pavement which will make the wheel start rolling backwards.
Summary:
Toe axis is purely of cosmetic value and has nothing to do with horse health, and changing the heel height will directly alter the hoof mechanism which affects the blood circulation and the health of the hoof.