Hoof Care For Your Horses
- Feb 1, 2006
The horse's leg below the fetlock joint is similar to the human finger; the long pastern bone, short pastern bone, and coffin bone are comparable to the three segments of a human finger. The hoof wall is made of the same material as our fingernails--keratin (a type of protein that forms hair, skin, and horny tissue). This specialized, tough shell protects the bones, nerves, blood vessels, and tendons inside the foot.
The hoof horn grows continually to compensate for wear and broken edges, growing down from the corium of the coronary band at the hairline. Just beneath the fringe of hair at the coronary band is the periople, a narrow strip similar to the cuticle on a human fingernail. It is a waxy, varnish-like substance that covers the outer surface of the hoof wall to protect it and prevent excess drying. When footing is soft and wet, the hoof becomes softer. When the ground is dry and hard, the hoof becomes drier and harder and can chip and crack more easily.
The hoof wall is made up of tiny tubules running down from coronary band to the ground, giving some elasticity to the wall so it can compress and expand without splitting. The tubules carry and hold moisture, but have no blood supply or nerves.
On the inside of the hoof wall, tiny leaf-like structures called insensitive laminae interface with sensitive laminae that contain a blood supply and nerve endings.
This interlocking attachment is what anchors the hoof wall to the coffin bone. If this attachment is disrupted by laminitis (inflammation of the laminae), the interface can come apart and the coffin bone might drop at the front or even completely sink within the hoof (founder).
The tough, outer covering at the bottom of the foot consists of the sole, frog, and bars. The latter are a continuation of the hoof wall, serving as braces to keep the heels from contracting. The V-shaped frog in the middle of the sole helps dissipate concussion. The sole and wall meet at the "white line" (it is yellowish at the sole edge and whiter toward the hoof wall side).
The digital cushion is a fibroelastic, fatty, pyramid-shaped pad in the rear of the foot. It lies above the frog and below and behind the coffin bone and navicular bone. When weight is placed on the foot, the rear parts of the hoof expand outward, and this pad is squeezed flatter between the frog, sole, and the coffin bone, compressing vessels and sending blood back up the leg. The expanding digital cushion pushes the elastic cartilages encasing it outward and back, dissipating the shock of impact like the gel-filled sole of a human athletic shoe.
Conformation of the hoof (heavily influenced by genetics) plays a large role in its ability to hold up with hard use. Feet should be well-shaped and of a size proportionate to the horse's size and weight. Hooves should be wide at the heels so they can spring apart to dissipate concussion and be less apt to bruise. The sole should be thick and somewhat concave.
Leg conformation (bone alignment, joint angles, and structures in the legs, whether the limbs are straight, base wide, base narrow, etc.) helps determine the shape of the feet because of the way they are picked up and put down--whether they are picked up squarely and land squarely, or start and end their flight crooked. A horse with crooked legs and poor joint angles will have feet that wear unevenly; one side of the foot will be a different shape than the other and the frog is usually pointed off center.
Many foot problems stem from the hooves not being in balance (due to incorrect trimming and shoeing, unevenness, or not enough wear), according to Tia Nelson, DVM, a farrier and veterinarian from Helena, Mont. Treating imbalance consists of bringing the foot back to balance with the horse's conformation--limb conformation is important in determining foot balance. For example, a horse with a crooked limb and a symmetrical foot will be sore because the hoof needs to be asymmetrical in order to land flat.
Feet must be balanced from front to back and side to side. A common balance problem is long toes and short (often underrun) heels. If the foot is not balanced side to side, there will be stress on joints, collateral ligaments, tendons, etc.
"People use terms like level, flat, and balanced as if they are interchangeable, but they're not," she explains. "The foot doesn't have to be level to be balanced, and being flat and being balanced are not the same thing. You can have a foot that's flat, yet 10 degrees off balance."
Bringing a problem foot back to balance (for that foot on that horse) is the first step toward soundness. A problem foot often can be corrected by putting a shoe on it, but balancing the foot itself is key. "I get
frustrated with the idea that we can put a shoe on a foot to fix it if you have not first corrected the balance," says Nelson.
It's Not Always Simple...
"People usually don't recognize that there are only two factors affecting the foot--genetics and environment," says Nelson. "The footing, the farrier, the food the horse eats, the ability to utilize the nutrients in the food, etc., are all part of the environment. These things are intertwined, and it can be hard to separate them."
She says some of her cases looked like they were insulin-resistant (with cresty necks, prone to founder, etc.), but weren't. When she was able to get their feet comfortable so they could get regular exercise, their glucose and insulin levels came down and their feet got better--without medical treatment.
"Fixing the mechanical cause of pain in feet that led to stress--that raised their cortisol (a "stress hormone") levels--resolved their problems," she explains. "When a horse gets painful feet, the cortisol levels go up, probably due to the stress and the ulcers that develop due to the stress. Stress hormone levels go up in any horse that's in pain. If his feet are out of balance and the stress on them starts to lead to founder, he'll be in pain.
"There are some horses, however, that are truly insulin-resistant," Nelson says. "It is our job to learn how to balance feet and get the horse comfortable again and to run bloodwork to check for these things.
"A lot of this has to do with giving horses diets appropriate to their species (forages rather than concentrates) and paying attention to what they're eating compared to what they're doing (exercise)," she says.
Some people want to resolve hoof problems by feeding supplements. In some instances, nutritional imbalances contribute to unhealthy feet and a supplement is necessary, such as when a horse is not getting a proper diet or is not absorbing or utilizing enough of certain nutrients.
"If a problem horse's feet are brought back to balance and maintained in a good environment with a supplement that contains biotin and sulfur-bearing amino acids, the feet will get start to get better," she says.
Common Foot Problems
Thrush is infection in the cleft and grooves of the frog, characterized by black, necrotic (dead), foul-smelling material. Lack of ventilation in the hoof (when it's continually packed with mud or manure) makes it more susceptible to thrush since the causative organisms prefer a damp, airless environment.
Poor trimming and shoeing (disrupting hoof balance or leading to contracted feet) also make a hoof more susceptible because deep grooves in a contracted foot hold more debris. Keeping feet healthy, clean, and dry is the best prevention.
Treatment consists of proper hoof care and trimming, along with daily cleaning. Application of a good disinfectant/astringent such as iodine or a commercial thrush medication can help, as can keeping the horse on dry ground.
White line disease ("seedy toe") is progressive separation of the hoof wall starting where the sole meets the hoof wall at the white line. Anaerobic pathogens (those that thrive in airless conditions) that live on keratin enter through a separation at the white line. This might happen if a hoof is too long or unbalanced, if wet conditions weaken the hoof at the white line, or if the horse steps on something that punctures this area. The opening collects dirt and manure, making an ideal habitat for hoof horn-eating microbes.
Keeping the foot healthy and properly trimmed and balanced can prevent white line disease. Treatment consists of removing diseased horn, opening it to the air, treating underlying tissue with a fungicide, and correcting foot imbalances.
Contracted feet are unable to expand and dissipate the stress of impact. Contraction of heels or feet might be due to injury, disuse of the foot (an injury painful enough that the horse doesn't walk on that foot, resulting in impaired circulation), improper trimming and shoeing, leaving shoes on too long, feet too small for the animal's body weight, or excessive hoof dryness. Ability to expand is essential to health of the foot. Restoring hoof balance and/or moisture to the foot will help.
Cracks in the hoof wall are often the result of long, bare feet that and split, concussion on a brittle foot, or injury. Brittle feet might be due to genetics, dry conditions, improper nutrition, or a combination of factors. If the hoof wall is kept short (by allowing the barefoot horse enough exercise on dry ground to wear his feet or by trimming) and the hoof balanced and healthy, cracks are rarely a problem.
Dry, brittle feet might be due to inadequate blood circulation (lack of exercise), extremes in weather/environment in which the feet are alternately too wet and too dry, frequent bathing, mud that pulls out the natural hoof oils, or standing in bedding (such as certain types of wood shavings) that dries out the hoof. Proper exercise and hoof balance, proper nutrition, avoidance of environmental conditions that destroy the hoof's natural protective coating, and using a hoof sealant to keep in moisture can be beneficial to help a dry foot.
Laminitis is destruction of the attachments between the sensitive and insensitive laminae that connect the hoof capsule to the coffin bone. The inner part of this interface is nourished by tiny capillaries. If blood supply is disrupted (from mechanical stress such as road founder or toxins in the bloodstream), it can lead to cell death in the laminae, compromising this attachment.
In severe cases, the coffin bone separates from the hoof wall. If the front of the coffin bone rotates downward, the horse needs long-term attention from a farrier. If the entire bone sinks, prognosis is poor.
Scott Morrison, DVM, a podiatrist at Rood and Riddle Equine Hospital in Lexington, Ky., says many laminitis cases are caused by problems secondary to the diet such as grain overload or grass founder, or problems metabolizing or regulating sugar levels (Cushing's disease or metabolic syndrome). With chronic laminitis, diet management is imperative.
"Some grass hay is high in carbohydrates," says Morrison. "Recent studies have shown that you can decrease the carbohydrate level in hay by soaking it in water just before you feed it, because the sugars are soluble in water.
"Sometimes we recommend feeding these horses a vitamin/mineral mix with the hay ration, to make up for what they are missing in grain," adds Morrison. "Some feed companies have special complete feeds for these horses--products that are low in carbohydrates, but still contain the necessary vitamins, minerals, and roughage."
About the Author
Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.