Trimming the Bars
What are the bars?
A cross-section of the heel structure. The bars grow at a slant, like the hoof wall, so the entire heel structure can 'give' when the horse puts weight on the foot. If the bars were vertical, they would jam straight up into the hoof.
Think of each bar as a little slanted board. Starting on the 'white line' side of the bars, trim along the edge of the bar so the board has a square corner, giving the hoof some traction on slippery ground. If you trim it off level with the sole, there is no traction.
An overgrown bar has a thin dirt line between the bar and the sole. Trim the bar and sole until you get to the bottom of the dirt line.
For curved bars, back up the toe. When the toe is not pulling the whole hoof capsule forward, the bars will straighten and contracted heels will widen.
The bars are a structure in the heel of the equine hoof. Looking at the bottom of the foot, you can see that the wall comes to a point on either side of the frog (the heel buttresses) and then bends forward to extend partway along the sides of the frog. These sections of hoof-wall material beside the frog are called the 'bars'.
What do the bars do for the foot?
We know the bars have several functions - there are probably more to be discovered:
- If we cut across the back part of a cadaver hoof, the outer wall, the bars, and the frog resemble an expandable, accordion-like structure, which is able to spread wider when weighted so that it acts as a shock absorber.
- When the foot is not weighted (is in the 'flight' part of the stride) the bars, as part of this expandable heel structure, act as a spring to bring the heel area back to its narrower position, ready to absorb the concussion of the next footstep.
- The bars, like the outer wall, have a 'white line' (laminae) which fastens the bars securely to the inner edge of the sole. Since the equine sole is only 3/8 inch (1 cm) thick, it's important not to shorten the bars below the level of the sole, as this would remove some of the bar-sole connection in this high-impact area, weakening the entire heel structure.
- In addition, the white line of the bars attaches the bars to the inner edges of the tail-ends of the coffin bone (the palmar processes). Because the bars grow at a slant, their laminae are underneath the coffin bone and do not suspend it like the outer wall supports the main part of the coffin bone. Instead, you could say they are keeping the coffin bone from slipping out of the hoof capsule - rather like your heel coming out of your slippers. Wouldn't it be nice to have a little patch of Velcro (hook and loop fastener) to keep your slippers on your heels? The horse has this.
What do the bars look like in a balanced foot?
In a hoof whose toe-to-point-of-frog is about 1/3 of the total toe-to-heel distance, the bars will be straight and flat. They will slant somewhat outwards -- if they were exactly upright, they wouldn't work as part of the shock absorbing expandable heel structure. Generally, horses that get enough daily miles (10+ miles, 15+ km) wear the bars to a sharp edge that sticks up about 1/8 inch (3 mm) above the sole.
What do the bars look like in a contracted or forward-toe foot?
In a hoof whose toe-to-point-of-frog is more than 1/3 of the total toe-to-heel distance (which means the toe is flared or 'long out in front') the bars will curve and will slant outwards more than straight bars, and will look like they are pressing into the sole beside them. This is what some people call 'laid-over bars.' If neglected, the bars can also grow some distance out across the sole, preventing the sole from growing to its full thickness.
When the toe has flared forward, the shape of the entire hoof capsule changes, pulling the heels together (what we call 'contracted') and forward (what we call 'underslung'). This shortens the space available for the bars, which have no choice but to curve. (Try squeezing one end of a postcard towards the other - the flat card must bend.)
How do we trim the bars in a balanced foot?
- When we trim overgrown heels down to the level of the sole, the back end of the bars is included in the rasping and will be in direct contact with the ground (it becomes part of the flat heel area). This part of the bars needs to be trimmed with the hoof knife (because the rasp can't go below the flat surface) just enough that it is not touching the ground.
- The rest of the bars may be worn enough by the horse so that no trimming is needed. If they are overgrown, there will be a thin dirt line between the overgrown bar and the sole. Trim the bar as described below until you have gotten rid of the dirt line.
- In trimming the bars, remember that they grow at a slant, not vertically. Trim the edge so that the bar is square like a board. To do this, you will trim more on the 'white line' side of the bar, and leave the 'wall surface' slightly longer (see diagram). The foot ends up with a little ridge that gives the horse some traction or 'skid-brakes' on soft or slippery ground.
How do we trim the bars in a contracted, flared-toe foot?
When a hoof has curved, 'laid-over' bars it is very tempting to 'do something about it' such as carving out the bars to 'let them grow in straight', or cutting a notch in the heels to 'make them de-contract'. THIS DOESN'T WORK and can harm the foot.
The solution to contracted heels and curved bars is to back up the flared or 'long-out-in-front' toe. When the toe is no longer pulling the hoof capsule forward, the heels will quickly widen, giving the bars room to straighten on their own. (See NHM Volume 7, Issue 3, Hoofcare Highlights, 'Forward Foot Syndrome'.) My horses' heels de-contracted 1/2 to 3/4 inch (1.3 to 2 cm) within six weeks, when I first discovered this solution after a year of trying to 'fix the heels by messing with the heels.'
Other than 'treating' curved bars by this counter-intuitive step of backing up the toe, we trim curved bars about the same as straight bars.
In a recently de-shod hoof or a flared hoof, the coffin bone is less firmly suspended within the hoof capsule and sinks down onto the sole corium, causing transition soreness, otherwise known as 'sore on gravel.' (For a more complete explanation of transition soreness, see the "Transition" page at www.barefoothorse.com.)
In these feet you will often find a raised or thickened area in the sole along both sides of the front portion of the frog. These are erroneously called 'bar pools' because they look like a forward extension of the bars (though they are in fact made of sole). The general consensus is that the hoof builds these raised areas to help support the middle of the hoof when it is not well supported by a strong white line connection. When the horse completes transition, and/or the flared wall has grown straight from the coronet with a tight white line, the 'bar pools' go away by themselves.
It is always tempting to shave off these raised areas to match the rest of the sole. I tried to do this when my own horses were in transition, and always ran into blood. Leave the "bar pools" as they are, only removing any chalky or crackled "old sole" on or near them. They will go away when the foot no longer needs them for extra support.
"Bar pools" may be semi-permanent in wet regions such as the northeastern United States, where hooves seem to flare easily and lose concavity due to the hoof being softer and the grass higher in sugar (which can cause inflammation and stretching in the white line). Horses in these regions should have their mustang roll renewed at least every two weeks to prevent new flaring. Where the wall is flared, it should be thoroughly rounded from the edge of the sole all the way to the outside surface of the wall.