The "mustang roll", or rounding of the edges of the hoof wall, was first noticed by observing the way the wild mustangs of the western United States wear their hooves through constant movement over abrasive terrain. Some form of a roll has become the hallmark or calling card of those who align themselves in some way as doing a "natural trim" and as anyone who knows us by now is well aware, we at Wild Hearts take the roll seriously! There is surprisingly much to it, to the point I had a hard time keeping this article short enough.
So what is the deal with the roll? What are some reasons why it's beneficial and important?
An actual mustang hoof showing off his naturally worn roll.
Perhaps most importantly, the mustang roll allows us to shorten a horse's breakover without shortening the vertical toe height beneath the coffin bone (which, especially on a front foot, could cause soreness). For our approach to trimming, if you extrapolated a line from the edge of the coffin bone to the ground, just in front of that is where we would like the hoof to leave the ground or 'break over'. Far too often there is excess hoof wall in front of that line, which delays the hoof leaving the ground and causes strain on the entire hoof capsule and limb of the horse. Long toes draw the hoof forward which collapses the bars forward and out, contracts the foot, contributes to thin soles, thrush, etc. It's bad foot mojo!
The orange line on this radiograph represents the approximate desirable location of breakover, with the blue
curved line to represent approximate location of the bevel/roll. There are other factors at work with the horse
in this image, but for the point of the discussion I tried to choose a pretty clear case of a toe which is too long!
The hoof wall is thicker at the toe from approximately 10-2 o'clock, and the lamina are closer in proximity in that area as well. I personally believe this is because the toe area has evolved over the history of the equine to be able to handle the demands of high wear in this area as a horse moves. The majority of domestic horses simply cannot duplicate that type of wear which causes the epidemic of long toes that we see.
INWARD VS. OUTWARD PRESSURE
The roll works with the ground to push the hoof wall and lamina against the internal structures, rather than a sharp or straight edge working against the ground to further pry away the wall from the hoof as the horse moves. Think of the end of a wooden broom handle that has been cut to a sharp edge, and then is ground into the ground. The edges would fray and pry away further with each impact. On the other hand, if the edge was rounded, as the handle was pounded into the ground the rounded edges would simply compact even tighter.
By "raising" the roll or putting on a steeper and higher bevel in areas of less wear on a less than straight horse (which is most of them!), we can balance the rate of wear more evenly across the foot. This means the horse will look and be more balanced as their trim cycle progresses.
The roll smooths the rough edges of damaged wall such as from nail holes or blown abscesses and a well done roll can make a hoof look neat and polished (and keep it that way, thanks to the inward pressure effect mentioned above). Many people unfortunately have associated a barefoot horse with neglect or lack of use, often because of the chipping and cracking that comes from a too-long trim schedule and a messy appearance to the foot. Clean, balanced rolls help eliminate this, and make a hoof look good visually as well as providing good functionality!
Roll, bevel, dubbing - the same thing?
Not really. A roll is a rounded outer edge to the hoof wall. A bevel is more about the angle we take with a rasp or nippers from the bottom of the hoof. We typically roll the top edge of our bevel. Dubbing is more like a thinning and bullnosing of the wall, and in my opinion not something that is positively functional for a hoof.
Mario applies a mustang roll.
You can over do a roll.
A weak, separated, shelly wall is not able to do its job of sharing the support load for a hoof, and may need to be rolled away for the short term while healthier wall is grown in. The horse may be fine with this but most likely will need to wear hoof boots for comfort until his hoof can perform better. He may even be more comfortable without the leverage on his hoof from the disconnected wall. But an otherwise healthy, well connected hoof can become sore and require boots if you roll away too much wall or start the roll too close to the sole - especially beyond the 10-2 o'clock point. Horses with already short upright toes, or with previously thinned walls at the toes, will not be able to have as big a roll as other cases. But with that said...
A mustang wears his roll onto his hoof every day through his constant movement. Our roll has to last as long as possible until we can re-trim the horse. In most horses in our area, even a big "Mario Roll" will last about four weeks before it fades away with the growth of the hoof. By a typical five to six week maintenance trim, most horses rolls are gone or nearly gone, but nothing has gotten away from us to where problems have begun. Small superficial chipping is ok and just cosmetic, but if there are bigger issues we definitely need to look at the diet, trim cycle length, hoof booting needs, etc.
"A good mustang roll is the best friend of natural hoof trimming" ~ Paige Poss, www.ironfreehoof.com
Sossity Gargiulo, Wild Hearts Hoof Care