Anatomy of a Trim
Why do we ask farriers to take knives and nippers (and sometimes a whole lot more) to our horses' feet every six weeks? For many of us, it has always been just one of those things you knew you had to do if you had horses. And we might have also wondered how to evaluate the trim when it was done.
To trim or not to trim, and how to trim correctly, are strong bones of contention in some circles. However, there are a few basic concepts that most accept as foundations of proper hoof care. We'll discuss these with experienced farriers in the following article to get at the meat of why and how to trim horses' hooves. Some of these concepts include trimming the sole, establishing proper hoof balance and angles, and dealing with conformational challenges.
As with anything, the more you know about what, why, and how, the better you can care for your horse--in this case, care for his feet and everything they affect.
Why Trim the Hooves?
"Because in nearly all domestic horses, the rate of hoof growth exceeds the rate of wear," says Mitch Taylor, American Farrier's Association (AFA) Certified Journeyman Farrier, director of the Kentucky Horseshoeing School in Mt. Eden, Ky., and chair of the AFA's Educational Committee. He notes that the following information is what the AFA teaches to new farriers and those going for certification.
"When you are viewing the foot from the side, it should grow at the same or at a similar angle to the pastern," he explains. "Therefore, the foot's bearing surface grows farther and farther out in front of the limb and coronary band (if the foot is allowed to grow too long). So your goal is to trim a long foot back to an appropriate length and restore a straight hoof-pastern axis (with the angle of the wall at the toe being the same as the pastern, which should be similar to that of the shoulder)."
But angles aren't everything. "Ideally, you want the same mass of foot in the front half as in the back half (see "Normal Hoof Anatomy and Balance" here)," he adds.
Length, angles, foot mass--these characteristics all help define a foot's suitability for a horse's job. But there is one more important one--the overall shape of the foot.
"Inside the foot, the front half is all bone," Taylor says. "In the back half, the components are all soft tissue--digital cushion, collateral cartilages, frog, tendons, etc. This half is designed to move and flex as needed for weight bearing. It's up to us (farriers) to be able to read the foot and visualize its internal components to reduce any abnormal internal tensions, shaping the foot so it functions correctly for what it needs to do. For example, if the heels get too long, they push forward and the quarters (sides of the foot) flare outward from the internal tension. Then the bars will bend and you have a misshapen foot.
"The functions of the foot are to bear weight, dissipate shock (energy), provide natural traction, and serve as a venous blood pumping mechanism," Taylor adds. "When feet are long, misshapen, or imbalanced, most of these functions still take place, but not as well. The foot won't dissipate shock as well, won't stand up to weight bearing, might slip, and won't circulate enough nourishing blood to grow good horn."
Trimming the Sole
While the hoof wall and white line are the foot's primary weight-bearing structures, the sole, frog, and bars also bear weight, although not as much. The sole also functions to protect the bottom of the coffin bone (P3), but weight bearing is a big part of its job. It contacts the ground and flattens with weight bearing, then becomes concave (curved upward) again when the horse picks up the foot and takes the weight off.
"The arch is a very strong shape," states Taylor. "But if you over-trim, you weaken it and reduce its depth and mass, reduce its protection for P3, and open the door for it to become flat, reducing its weight-bearing ability. A barefoot horse will load his sole on soft ground anyway, so you won't save it from bearing weight by cutting more off.
"If you can palpate the sole and it yields to thumb pressure, think what will happen when a horse steps on a rock," he says. "It shouldn't yield much at all."
Hoof balance is another area where you will find as many opinions on achieving and measuring it as the number of people you ask. However, most agree that symmetry, or near symmetry, compared to the leg's conformation is the right concept. (If perfect symmetry isn't present in the leg, then you shouldn't strive for it in the hoof--more on that in a moment.)
"Proper static balance (hoof balance when the horse stands still) is directly correlated to dynamic balance (hoof balance in motion, such as breaking over and turning)," Taylor explains. "One aspect of balance can be looked at as mediolateral (inside to outside) to make sure the hoof is not longer on one side than the other, and the heels are the same length.
"You want joint congruency (equal loading across a joint surface), i.e., you are not pinching one side or the other," he continues. "If the foot is balanced correctly, the joints are loaded evenly as well. If you left the inside of the foot high (longer than the outside), for example, then the inside of the joint capsules would be compressed and eventually crush the joint cartilage, and the outside would not be loaded much. The outside would actually be pulled open (under tension), as well as undergoing pulling on that collateral ligament (which lies on the side of the joint and helps stabilize it)."
Balance isn't just a left-to-right concept when it comes to the horse's foot. "The other plane is the toe to heel ratio, also called the anterior/posterior, dorsopalmar (front foot), or dorsoplantar (hind foot) ratio," Taylor continues. "A long heel is a weak heel; shorter is stronger. Most horse people think a long heel is best because it helps breakover. Balderdash. It's important to keep the heels and toe in the right proportions so the foot can load itself as it was designed to do. Longer heels (relative to the toe) are more likely to crush, flare, and collapse in on themselves. Then you have internal impingements on tissues and coriums (sensitive structures that "grow" different outer hoof structures such as the sole or frog), heel-sore horses, and atrophied frogs."
Taylor continues, "As farriers, we're always fighting people who think a horse needs a lot of heel (but not a lot of toe). When trimming the heel, you also need to trim the toe to keep things in balance."
What to Look For
So how can you tell if your horse's feet need a trim, or if the latest trim was done properly? First of all, be present and attentive when the farrier works on your horse so you can ask questions as they occur to you. Also, you can then learn about conformation problems your horse might have that could affect his trimming and shoeing.
"In an ideal situation, a horse's front or hind pair of feet is matched; those feet are mirror images of each other," says Taylor. "Usually there is a bit more mass to the outside of the foot than the inside when viewed from the bottom, and so the wall angle is a little different outside. However, many horses have conformation problems that give you mismatched and/or asymmetrical feet--such as toeing in or out, being bowlegged, etc. What we try to do is position the foot as closely underneath the bony column of the limb as possible.
"Also, you want any wall flares taken off, and a nice pasture roll (rounded edge on the end of the hoof wall) to minimize chips and splits," he adds. "You also want to see the commissures (sulci on either side of the frog and in the middle) opened up for self-cleaning, with the dead, ragged parts removed."
Something else you can look for, says farrier Julie Plaster of Moberly, Mo., is that the hoof wall thickness (from the white line to the outer edge of the hoof; this is most easily evaluated in a freshly trimmed foot) is uniform all the way around that foot.
About half of the trim job is done on the bottom of the horse's foot, Taylor says, where the sole and wall are trimmed vertically. The rest of the job addresses the sides of the foot, removing dishes and flares (which will hopefully be minimized in the future by proper balanced trimming on a regular schedule). When feet are well maintained, not much work needs to be done on their outsides.
Remember that evaluating a trim isn't quite as simple as checking for open commissures, a smooth sole, and a nice rounded hoof edge. "The main thing for owners is to understand the normal conformation of the foot, admit that their horse might have hoof and/or leg conformation faults, and try to understand what those faults do to the conformation of the foot," notes John Arkley, an AFA Certified Journeyman Farrier in Wasilla, Alaska. "So learning more is key," especially learning what the farrier can and can't do with that particular foot.
"We see so many bad legs," he continues. "People will say, 'It didn't look like that before you worked on the horse.' It's like when the conformation problem is unrecognized, it doesn't exist and the horse is perfect. Then when you point it out, they think it's new. This is particularly a problem with owners who don't know what they're looking at but think they do. It's a very tough scenario."
Keep in mind that you can't correct leg conformation problems in the adult horse just with trimming and/or shoeing--and you can't create them either. Regarding correction, Arkley says, "You can't play God and fix these horses. You will end up with a cripple every time."
So the idea is to maintain a hoof shape that fits the horse's conformation and helps him do his job comfortably without hoof distortion (flares, etc.). Case in point: At a boarding/trail barn where I used to work, we had a Quarter Horse-type gelding which stood like a bulldog in front. He had a wide chest and obvious bowlegs, and he paddled out, dragging the outside of his toes, as he moved. He was barefoot, so he wore a flat spot on his toes where he dragged them. He wasn't the slightest bit lame, just crooked.
Then someone decided it would be good to trim his feet to a "normal," consistently rounded shape and add shoes to stop the abnormal wear. Right away, he was very uncomfortable--and he stayed sore until the shoes came off. The moral: Sometimes a horse is a lot more functional with his natural adaptation to an imperfection than he is if you try to make him perfect.
"It's the owner's responsibility to get the farrier out there on a regular basis to trim the feet and properly manage their growth patterns," says Taylor emphatically. "If we only trim a horse twice a year, we're just doing damage control (trying to fix something that's messed up), because there's not enough good foot to build on. The farrier's responsibility is to get the foot to grow down straight and strong without flares and such, but he can't do that if he's not there."
"It's more cost-effective to maintain balanced feet rather than trying to fix them later," adds Plaster. "Make sure the horse is balanced by starting with the feet. They are the horse's foundation."
The horse's attitude toward having his feet handled for trimming also has a big impact on the work. "I like to make sure the horse understands and will allow his feet to be worked on," Plaster comments. "That alone has a big impact on what kind of trim you get. I teach clients to train each horse to pick up his feet and stretch them forward. Forward stretching with a little forearm massage on each front leg is good to help them relax." Also, she says that having a comfortable, safe place to work on a horse makes it easier to focus on the job at hand and do it justice.
However, preparation isn't enough without feedback. "It's necessary to discuss your ideas, questions, and concerns with the hoof management and work being done. This is a team concept--each player has a role," says Plaster. "The owner who sees and works with the horse frequently would most likely know when the horse is off, but might not be able to identify what the problem is or how to fix it. The owner's, farrier's, and veterinarian's roles and perspectives are critical, as well as those of the horse himself."
The Perfect Trim?
What this all boils down to is that the perfect trimmed hoof shape for your horse might cripple another, so it's impossible to make hard and fast rules regarding what makes a good trim. Because of the diversity of biology, no two organisms are exactly alike. Additionally, common hoof challenges differ from place to place, likely based on environmental moisture content and grass composition.
There are certainly guidelines for maintaining soundness, but those guidelines (both for trimming and shoeing) must be interpreted in the context of each individual horse's conformation. The owner must understand and accept the challenges that particular conformation presents. The perfect trimming prescription for your horse is the one that keeps his feet healthy while he's doing his normal job, whatever that hoof shape and length happen to be. "If the foot has maintained equal growth patterns and minimal distortions over a period of time, it's happy, and so am I," Taylor concludes.
Trimming/shoeing guidelines and farrier/horse owner clinic schedules: www.americanfarriers.org/horse_owners/index.aspx.
West, Christy. Shoeing in the Frontal and Horizontal Planes. Article #4252 at www.TheHorse.com.
What About All Those "New" Trim Methods?
In every industry you could name, there are innovators who develop and market "new and improved" ways to do old tasks. Some of these new methods have valid, repeatable, improved results in a wide range of similar situations. But some are just marketed to have that success, and fall a bit short when it comes time to implement them.
Trimming horses is certainly no exception, particularly because there is a notable lack of scientific study in this field. This allows anyone to develop a procedure and call it the best thing that ever happened to horses. And in the United States, where farriery is unregulated, owners who don't see the results they would like from one farrier can always find another who's willing to try the latest fad. But is that fad really better than "traditional" methods (such as those taught and tested by the American Farrier's Association, or AFA)? Mitch Taylor, an AFA Certified Journeyman Farrier, director of the Kentucky Horseshoeing School in Mt. Eden, Ky., and chair of the AFA's Educational Committee, gives us his thoughts on the situation.
"Are there horses out there that could use these things (new trimming/shoeing methods)? You bet! But there is no way all horses need these things. All horses are different!
"The problem is that anyone at all can go out and shoe a horse, but they don't have to be properly trained. So if they don't get the results they want, they will often reach for the gimmicks. Owners who reach for these gimmicks are often frustrated by the incompetence of a poorly trained farrier or don't want to pay for a good farrier. It's a spinoff of a free society."
"If this carries on for too much longer, someone will anger the wrong person, and they'll go to the legislature (to ask for governmental regulation of farriery). And those who pass laws will be people who don't even know what a horse's foot looks like."
The way to alleviate this problem, he believes, is through better-educated farriers who can use their skills and training to keep horses sound and performing without the need to try the latest fad on horses.
"The AFA Education Committee's first goal has been to educate farriers to pass the certification exam, and we've raised the passing rate from around 15% to 55-60% with certification clinics," he says. "You will do better by using a certified farrier. Certification doesn't mean a farrier can't have a bad day, but at some point, that farrier demonstrated his/her theoretical understanding of the horse's foot, passed a two-level practical test of shoeing under time constraints, and showed the ability to competently handle shoe modifications as judged by a panel of professional horseshoers."
Also, says farrier Julie Plaster of Moberly, Mo., if owners require their farrier to have a proven level of farriery knowledge (such as AFA certification), then there will be less work for farriers who haven't proven this level of skill. Then there will be a bigger incentive for those farriers to prove their skills, perhaps learning more about the horse's foot in the meantime.
"Our next goals (with the Education Committee) are to educate owners and veterinarians about managing the horse's foot," Taylor concludes.
About the Author
Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.