A horse's feet take quite a beating. When you think about it, it's amazing that a structure which is basically a thicker version of our own fingernail can support the weight of a horse and hold up to the varied terrain they travel over. As tough and adaptable as a horse's hoof is, it's not indestructible. This article will take you through the basic anatomy of the foot, the nutritional influences on hoof wall quality, and trimming and other details of hoof care.
Total Hoof Health
- Hoof health starts with correct and timely trimming. The importance of this job cannot be overstated.
- Nutrition is the next key element in achieving healthy feet. Feed a correct, balanced, and adequate diet overall.
- Ensure that your horse's total diet provides enough protein and amino acids in the correct amounts.
- While moisture, or the lack of it, gets blamed for many hoof problems, the underlying culprit is usually nutrition or poor trimming practices.
External Anatomy of the Foot
Starting with the bottom and working in, here are the external structures of the foot.
Hoof Wall Horn: This is the tough outer layer of the hoof wall. Composed primarily of protein, fatty acids, and cholesterol, it forms a waterproof barrier. This dead, insensitive tissue is much like the white ends of your own nails that protrude past the skin of the toe or finger.
White Line: This is a thin line of tissue that contains the laminae, interlocking "fingers" (think Velcro) that connect the hoof wall horn to the live tissues inside the foot. The white line contains live, sensitive tissue only as far down as the coffin bone extends. Below this, the white line is also dead, insensitive tissue.
Sole: The sole is produced by laminae along the bottom surface of the foot. It is similar to the hoof wall horn, but has a bit more flexibility.
Frog: Moving backward from the toe, the V-shaped fleshy structure is the frog. Although similar to the sole and the hoof wall horn in make-up, the frog is much more compressible and rubbery. It's designed to function as a shock absorber. The frog normally has a cleft down its middle, which should line up with the cleft between the heels.
Bars: If you follow the outline of the hoof wall horn back to where it ends at the frog on either side, you will see it makes a turn inward along the frog and continues to follow the outline of the frog. These extensions of the hoof wall horn are weight-bearing surfaces of the hoof for part of their length, and also extend up inside the hoof to create a support for the coffin bone.
The hoof wall horn is produced by the coronary band, a transition zone between the skin of the pastern and hoof horn, like the nail-producing cells at the bottom of our own nails.
Internal Anatomy of the Foot
Moving to the inside of the foot and working out, first let's discuss the bones. The very bottom of the pastern bone (P2 = second phalanx) and the coffin bone (P3 = third phalanx) are inside the hoof capsule. Attached to the back of the coffin bone on either side are "wings" of cartilage called the lateral cartilages. These are more flexible than bone, expand on ground contact, and help with shock absorption and blood flow.
The next layer is the corium, a dense network of tiny blood vessels that supply the coronary band and surround the coffin bone on all surfaces, like a hair net. The parts of the corium are further subdivided into laminar corium, supplying the laminae; solar corium, supplying the cells producing the sole; and frog corium. The blood supply to the corium comes from the digital arteries, which are a pair of arteries that run over the back of the fetlock joint and pastern before dipping into the foot.
Finally we have the digital cushion. Think of this as similar to gel inserts in a human running shoe. The digital cushion is a combination of fat and connective tissue that sits inside the hoof capsule above the frog. Like the frog, it absorbs shock and protects the coffin bone, coffin joint, and navicular area when the hoof contacts the ground.
The Importance of Trim
To understand how critically important correct trimming is to the health of the foot, let's go back to the running shoe analogy for a minute. Beginning with the corium-the vascular tissue surrounding the coffin bone-the soft tissue structures inside the foot conform to the bone column the way your sock conforms to your foot. Your sock is the equivalent of the laminae, a "layer" between live tissue (bone, corium, digital cushion) and dead/insensitive tissue (hoof wall horn, sole, frog). The hoof capsule itself is equivalent to your shoes. The coronary band, hoof wall, frog, and sole conform to the bones and soft tissues the way a well-fitted running shoe conforms to your foot and sock.
If you were to glue a sock to your foot and your shoe to the sock-the way the interlocking laminae glue the outer hoof structures to the sensitive internal ones-it would still be comfortable as long as everything fit properly. However, if the shoe expanded too much away from the sock when you walked, it would pull on the sock and foot, causing pain. This is what happens when the toe of a horse's foot gets too long or flares. Similarly, if the shoe was fixed in place and the foot tried to move away from it, this would also tug and cause pain. This is what happens in cases of laminitis, when the damaged laminae get torn and the bone can rotate or sink.
It's probably safe to say that more hoof problems are caused by failure to correctly trim the feet than any other cause. As everyone knows, there are multiple trimming styles available today, each claiming to be the best. However, the proper trim is one where the hoof capsule correctly conforms to the structures within it.
If you think you can forget about trimming details because your horse wears horseshoes, you're mistaken. Shoes can sometimes help redirect forces in the foot in a better way, but the key to foot comfort and good support-whether wearing horseshoes or not-is still a good trim.
There are some basic principles you can use to evaluate your horse's trim. This checklist is far from exhaustive, but will give a good idea of these principles. (Note: these may not apply to severely deformed feet.)
• The center of weight-bearing in the foot sits just slightly behind the tip of the frog. When looking at the bottom of the foot, there should be an equal distance from this point back to the heels as there is from this point to the tip of the toe.
• The widest part of the foot at the ground surface should also be located close to the center of weight-bearing.
• The white line should be tight (normally about 1/8 inch in width) and the same width all around the foot.
• The thickness of the hoof wall at the ground surface should be about the same all around the foot.
• The height of the bars should be level with the hoof wall at their start but gradually taper down lower as they progress along the side of the frog.
• The frog should contact the ground when the horse is bearing weight.
• When viewed from the side, the coronary band should slope gently down toward the ground at approximately a 30-degree angle.
• From behind, with the hoof on the ground, the heel bulbs should be of equal height.
• Walking, the horse should land heel first.
In short, the hoof capsule should be centered around the center of weight-bearing so that forces are distributed equally and the bone column is properly supported. If you look at the horse's hoof while bearing in mind that it's really the equivalent of your own shoes, it's much easier to see how important the trim is. The strain of trying to move in shoes that don't fit can end up hurting your feet and causing problems higher up in your legs or even in your back. The same is true of a horse with an incorrect trim.
Feeding the Feet
Dr. Steve Jackson, whose doctoral work focused on equine nutrition, presented a paper 12 years ago on nutrition and how it affects your horse's feet. This paper remains a classic and is still pertinent today. Anyone interested in this topic can read it at: http://www.horseshoes.com/advice/jackson/ntanteqf.htm.
The basic premise of Dr. Jackson's paper-and I couldn't agree more-is that the best and only way to guarantee that the diet of the horse is providing correct and adequate nutrition for the feet is to feed a correct, adequate, and balanced diet overall. There are no magical ingredients for growing healthy feet. However, there are some common deficiencies that will strongly impact the health of the feet.
When a horse has a dietary deficiency/insufficiency, it very often will show up in the feet and/or hair coat first. This is because the horse's body will conserve nutrients for more critical tissues like heart, brain, organs, and muscle if there is a nutrient shortage. It just so happens, too, that many of the nutrients most important to hoof health are also commonly borderline low in the diet anyhow.
Protein and Amino Acids
As already mentioned, the hoof tissues are composed primarily of protein. Many people fear protein, thinking (incorrectly) that it can damage the horse's kidneys or even cause laminitis. The truth is that young stands of growing grasses often contain over 20% protein. Most people are very familiar with how great horses look and how rapidly their feet grow on this type of pasture. You do, however, have to make sure that the horse is getting adequate protein. Horses most at risk of having too little protein are those being fed primarily very mature cuts of grass hay or those on failing pastures.
Amino acids are the building blocks of protein. Picture a protein as similar to a chain of different colored beads. Every color represents a different amino acid. The horse's DNA holds the code for how the amino acids need to be combined to make each specific type of protein. A limiting amino acid is one that has to come from the diet because the horse cannot make it himself. It is also an amino acid that will limit the horse's ability to assemble protein chains if that specific "bead" is not present in an adequate amount.
Deficiencies in specific amino acids are more common than a deficiency in the total intake of protein. Every protein has a different sequence and different amounts of specific amino acids. Believe it or not, a horse being fed large amounts of grain and limited hay/pasture is actually more likely to run into problems with inadequate intake of amino acids critical to hoof health.
Hoof horn contains high levels of the amino acids cystine, tyrosine, and threonine. Threonine is an essential amino acid, meaning it must be present in the diet. The horse's body can manufacture tyrosine, but needs the amino acid phenylalanine to do it. Cystine is very important to protein structure in the hoof. This can be manufactured too if there are adequate levels of the amino acid methionine. A deficiency of any of those amino acids, or of lysine, which is the major limiting amino acid in horse diets, can have a negative affect on hoof growth and/or quality.
Getting back to the diet, the problem with high-grain diets is that grains are low in lysine and threonine. The soybean meal so commonly used to boost protein in equine diets is low in methionine. Also, because grains are so much more calorie dense than hay or pasture, you have to feed less to avoid the horse getting fat. This can mean that the horse on a high grain diet actually gets less protein than one on straight hay.
The bottom line: Your first step when you have hoof growth or quality issues is to ensure that your horse's total diet provides enough protein and amino acids in the correct amounts. If not, whey protein concentrate is a protein supplement that contains these key amino acids in amounts very similar to what the National Research Council's new 2007 recommendations suggest is ideal for horses. You can find whey protein concentrate in health and bodybuilding stores, and there are many online sources.
Why Don't Feral Horses Need Trimming?
Horses were on this earth long before man developed tools to trim their feet. How did they manage to avoid crippling foot problems? The answer is exercise, and plenty of it. It has been estimated that wild horses cover a minimum of 20 miles a day, far more than any domesticated horse does. That much exercise will cause excess dead wall to chip off or be worn down. This process is called "self-trimming."
Minerals Help Grow and Repair Tissue
Adequate and balanced mineral intake is critical to the repair and growth of all tissues. There is no single mineral that adds to hoof quality more than another. The important thing to remember about minerals is that more is not better. If the diet is adequate, excess minerals won't help and may actually cause problems. The solution to mineral problems that might be influencing the feet is simply to get the whole diet balanced. Otherwise, it's pure guesswork.
Zinc is a common ingredient in hoof supplements, but it's not because of some special affect it will have on the foot. It's because zinc is a common dietary deficiency. So is copper, which is crucial for the formation of connective tissue. Be suspicious of zinc and copper deficiencies if you begin to see reddish/rusty discoloration of dark hairs.
Biotin is a B vitamin commonly used in hoof supplements. This is based on some equine studies that found improved growth and hoof quality, although to varying degrees. Since biotin is important for the health of skin and coat as well, this isn't too surprising. The usual dose is 10 to 20 mg/day. If the horse is also being heavily worked or on a high-grain diet (pasture and hay are the major sources of B vitamins in a horse's diet), supplementation with a multiple B vitamin may also help. In fact, a strong case could be made for vitamin C and vitamin A too. Once again, an adequate and properly balanced diet is the real answer and will virtually eliminate any hoof growth or quality issues that are tied to nutrition.
As mentioned above, the hoof's ability to retain its internal moisture and avoid excessive uptake of water is related to an outer barrier of fat. This is what gives healthy hooves a slight sheen. The horse can manufacture all the various types of fat he needs (triglycerides, cholesterol, etc.) from other materials in the body. There is no dietary required level of fat, except for the omega-3 and omega-6 fatty acids that the body cannot manufacture itself. Requirements have not been firmly established, but we can take our clue from the horse's natural food: fresh grass. Grasses have roughly 6% fat, and a ratio of omega-3 to omega-6 of at least 4:1.
When hay is cut, dried, and cured, the fragile omega-3 fatty acids are lost, as are some of the omega-6s.
Flax is the only commonly available high-fat supplement that contains the essential fatty acids in proportions similar to fresh grass. Supplementing with 4 to 6 ounces/day of ground flax seed will replace the lost fatty acids for horses that are not on fresh pasture.
Other Hoof Care Issues
There is much confusion about moisture and hoof health. Some say a wet environment is harmful and dry is better. Others say feet should be soaked every day. Still others say the worst thing for the hoof is going back and forth between wet and dry, as when hooves are exposed to moisture from dew then dry out over the day. The truth of the matter is that healthy horses' hooves are very adaptable to their environment. Arabians do splendidly in the harsh, dry desert, while the wild horses of the Camargue in France spend their time in marshlands.
While moisture-or the lack of it-gets blamed for a lot of hoof problems, the real culprit is usually nutrition or poor trimming practices. For example, going too long between trims sets the horse up for chipping and breaking. Rasping of the hoof capsule removes its moisture barrier. Failure to get the foot landing evenly leads to overloading of one side and improper breakover of the foot, increasing the risk of chipping and cracking.
When horses are kept under very dry conditions, their hooves naturally compensate by becoming very dense, to withstand the hard ground. This does make them difficult to trim, but there's actually nothing wrong with the feet. While most horses' feet are exposed to moisture in some form during the day, this is not necessary for the hoof to have a normal, healthy moisture level. The hoof is designed to keep outside moisture out and inside moisture in.
Domesticated horses may have more problems under constantly wet/muddy conditions than feral horses do simply because trimming the feet inevitably removes their protective layer. The horse's hoof may absorb more water than it normally would and the softer walls may spread more, leading to traction on the white line, even infection gaining access to the white line with the result of either white line disease or abscesses. However, keeping the feet well trimmed at all times is still far preferable to leaving them alone, since this will eliminate any stressful mechanical forces on the feet. If your horses have a dry area that they can go to for at least part of the day to allow the feet to dry out and mud to fall off, this should be adequate protection for their feet. If you're still having problems, a hoof sealant can be applied to areas that were rasped after the horse is trimmed.
Standing in manure or urine is another matter entirely. Unfortunately, few domesticated horses have enough room to move around to completely avoid getting manure packed into their feet. But if they can move around so that it dries and falls out, fine. Otherwise, thrush is likely to result. Horses that aren't loading their feet properly because of incorrect trim or a pain issue are at the highest risk. For this reason, picking out the feet on a daily basis-including a visual and "sniff" inspection for thrush or thrush odors-is important to maintain healthy feet.
Exercise is important to all parts of the horse, and the feet are no exception. When the horse's weight comes down through the hoof, the hoof naturally expands a bit and pops out any material packed into the foot. This action also leads to any excessive dead sole build up being shed. Exercise encourages good circulation, stimulates growth, and activates a thicker wall and frog and a denser digital cushion. However, the catch here is that these good things will only happen if you are providing a correct diet and the trim is allowing the hoof to function mechanically in the way it is supposed to function.
Finally, there are even more hoof lotions, potions, paints, and dressings than there are hoof supplements. But do you really need these things? If the hoof is properly nourished and trimmed, you won't even be considering the use of any of these products because you simply won't need them. However, if you're still in the process of getting your horse's feet healthy, they may be of some use to you.