Poor genetics, environment, nutrition, and foot care are the main causes of thin, shelly feet according to Ken Marcella, DVM, and farrier Jaye Perry. Marcella co-owns Chattahoochee Equine in Canton, Ga., and Perry, a farrier based in Cumming, Ga., has a large clientele of hunter-jumper and endurance horses as well as pleasure horses. Both men have practices all over the United States, with Marcella also working in Canada and Europe and Perry in England, France, and the United Arab Emirates. Both agree that environment is the number one cause of shelly feet.
"Ideally the hoof wall or horn, as it is called, is comprised of 15-25% water, and the frog is closer to 50% water," says Perry. "When a horse's feet are exposed to excessive moisture, the structural integrity of the hoof is comprised. The horn tubules become saturated, and thus become more elastic.
"Often, especially in the South during the hot and humid months, horses are turned out to pasture at night and stabled during the day," he continues. "The purpose is to protect their coats from the harsh effects of the sun and give relief to the horse from the annoying flies. But east of the Mississippi, the humidity produces a lot of moisture through the night that creates heavy dew on the grass. If the horse is maintained in wet pasture, or in a barn with wet stabling conditions, he will have wet, mushy feet. A horse's feet will mirror his environment."
Marcella adds, "While the horse needs a certain amount of moisture to produce good feet, anything that goes beyond tends to weaken the laminae. Weakened laminae won't hold weight as well and are prone to cracking and damage, which results in shelly feet.
"Shelly feet means poor-quality hoof walls that are brittle, cracking, and flaking," Marcella explains. "It sounds like a contradiction that excessive moisture can cause dry, brittle, flaky hooves, because you would think they would need more moisture. But actually it is the moisture that causes the damage to the laminae, then the hoof wall becomes weak, then dry and flaky.
"If you are constantly changing what the hoof laminae are exposed to, causing them to swell and then dry out over and over, that weakens the support," he says.
Marcella likened the weakened hoof to bending a paper clip back and forth over and over again. Eventually it will crack or break.
Identifying the Problem
Perry describes what shelly feet look like: "From the ground surface or sole, shelly feet have a very thin horn (wall), with no uniform width to the wall or white line. Usually there is breakage and chipping around the solar margin (where the hoof meets the ground) portion of the wall. The sole is often flat, and sometimes there is a slight convex (outward curve) to the toe region of the sole and/or coffin joint area.
"From a lateral view, you will see chipping and cracking," Perry continues. "Cracks may be vertical, with some as high as the coronary band, but with no depth into the sensitive laminae. The individual horn tubules can be seen in an up-close study. There is often a slight dish to the dorsal portion of the toe.
"Viewing from the front, the shelly hoof has an hour-glass appearance that is usually just slight, but in some cases can be dramatic. Chipping and cracking is also seen," he adds.
The structural integrity and growth of the hoof can be affected by the nutrition of the horse, or his lack of nutrients.
"A horse needs to have a good-quality diet, enough protein, and the right amount of vitamins and minerals to grow quality feet," says Marcella. "Most every feed company that you deal with now fortifies their feeds with vitamins and minerals. So getting the horse on a commercial diet, along with good-quality hay or pasture and free access to good water, is often all that is needed to grow good hooves."
Perry says, "The horse industry offers every combination of feeds and supplements known to man. Many horse owners, trying to get a better edge on the next guy in their respective competitions, give their horse far more than the horse's body needs. Horses end up with an unbalanced diet due to all the feed and supplements they receive. Having something as small as an imbalance of copper can make a difference in good feet and bad feet."
Marcella agrees. "There are certain minerals and vitamins that play an important role in growing the hooves. If the horse is getting improper nutrition, then that translates into poor growth of all the horse's tissues, which is reflected in the hooves. The hoof grows only as fast as the smallest mineral that is important to the growth process.
Marcella explains that if a horse is lacking in any needed nutrients, you could feed four tons of biotin, but as long as you are low in that nutrient, that is as fast as the hoof is going to grow.
"One of my pet peeves," Marcella says, "is all the buzz about biotin. It certainly is an important part of foot growth, but all the research done on biotin and foot growth was done on pigs and chickens. There was very little research done on horses, yet all that research was appropriated for horses. And, what is not fully understood by the general public is that without certain trace minerals, the biotin is not properly absorbed and utilized.
"I am not a huge supplement fan," continues Marcella. "A balanced commercial feed works better than one specific supplement in excess."
There are blood tests that can be done to check the levels of such things as selenium, cobalt, and magnesium. However, these tests are so expensive that unless you are having a huge problem, they are not recommended. According to Marcella, you could put the horse on a good, balanced vitamin-mineral supplement for six months for what it would cost to run the tests.
While Marcella and Perry say environment is predominantly the cause of shelly feet, Marcella says, "You must assess the whole horse. A horse's feet are an extension or expression of the entire animal's health and well-being.
"Is the horse under stress from a medical problem? Does the horse need dental work? Is there an underlying disease or weakened immune system that makes it less likely for the horse to digest and absorb the feed and supplements he is being fed? Is there anything going on in the cardiovascular system?" questions Marcella.
Although genetics can play a part in the condition of horses' feet, Marcella says hoof quality is often due to how the horse is managed. "Some breeds lead a more normal existence (pasture turnout with free exercise), and others have a lot more human manipulation (stalled with controlled exercise)," he says.
The quality of foot care is just as important as nutrition and environment in preventing shelly hooves. When a horse's foot hits the ground, shod or unshod, it should expand a bit. If the horse's shoes are too small, the nails can restrict the foot from expanding. As a result, the foot takes more concussion than if it were allowed to expand.
"If the only part of the foot that is shelly, brittle, and cracking is from the nail holes down, you need to consider another cause other than genetics, environment, or nutrition," says Marcella. "And for those horses shod only in the front feet, unless there is a circulatory problem, there is no reason that only the front feet are involved. (However, because the front feet inherently carry 60% of the horse's weight, and the back carry 40%, the problem can be worse in front.) In either case, you need to study how that horse's feet are hitting the ground and how the weight is being distributed."
"This is true for any horse," adds Perry, "whether the horse has good feet or bad feet. Load distribution plays an essential part in foot stability and horn structure. Proper balance of the foot, conformation of the horse, and discipline involved will dictate how the circulatory processes will either compromise or enhance the foot's structural integrity.
"There are numerous techniques for trimming feet, and today's so-called 'latest and greatest' methodologies only portray the perfect foot, thus are only looking from the coronary band down," continues Perry. "However, the horse's foot is shaped from the upper body weight loads. These loads are dictated by the leg conformation that influences leg flight and the five phases of the foot in stride--impact, load, stance, breakover, and lift off. Trimming should be done so that the clinically sound horse impacts and loads the foot as flat as possible, and the breakover complements the foot and leg flight of the horse rather than as a forced action.
"Type of shoes used should complement the structural integrity of the horn," says Perry. "If the feet are thin-walled and shelly, in most cases steel shoes of proper width and heel support would be used. The use of toe clips is recommended. If aluminum shoes are required for the horse's discipline, a bar shoe is a good choice. The nails should be placed as far forward as possible, and in some circumstances extra nail holes may be needed. If weight of the shoe is a factor, plastic shoes may be beneficial in certain circumstances.
"Pads can be added, especially for the thin-soled feet," continues Perry, "and leather is the best because the leather will 'breathe.' Leather also allows for an expansion and contraction in which moisture content of the foot is better regulated."
Setting shoes too far forward or too far back compromises the balance of the weight-bearing and expansion and contraction functions of the foot, says Perry. Setting the shoe forward might cause excessive stress at the toe quarters in the breakover phase. This can create an abnormal bend of the horn midway up the dorsal wall in the toe. If the shoes are set too far back, the stress is somewhat similar, but the breakage occurs farther back in the foot.
Marcella explains that there are two parts of the foot that you will treat--the coronary band and from the nail holes down. If the horse has shelly feet, Perry recommends a hoof dressing with lanolin and beeswax for around the coronary band.
Marcella points out that foot grows from the coronary band and blood flow from the coronary band to the foot is important for growth.
"You want to promote growth at the coronary band, so you use products that are emollients or softeners and that have a lot of vitamins and minerals in them," says Marcella. "In putting ointments on the coronary band, it is not always the case that vitamins and minerals are absorbed. However, there is good data showing that solutions of aloe, vitamin E, and other vitamins and minerals have positive effects on skin growth and are beneficial for hair and horn production. Putting these solutions on the coronary band has long been standard practice, but I have seen no research data investigating this. I use these types of products to help promote the growth and keep the foot moist. Products with lanolin go on that coronary band and upper part of the foot. Using a lanolin-based product or even Vaseline, massage the soft tissue (skin) of the coronary band with a soft toothbrush. It is the massage that does more good by increasing the blood flow in the particular area. Using a toothbrush to stimulate blood flow to the coronary band is a clinical observation as well.
"I have taken thermography scans that show increased heat patterns that involve the entire hoof and the heels, and not simply the area stimulated," Marcella continued. "Studies using cold laser or light therapy have also shown that treating the blood vessels of the coronary band gives an increase in flow to the hoof."
"The bottom third of the foot--from the nail holes down to the bottom--is essentially dead hoof," Marcella says. "You want that hard and dry. You don't want to soften that. That would be comparable to the ends of your fingernails. So what you put on the lower part of that foot would be things like iodine, mersol (a solution of thimersoline), and similar compounds that are drying agents that keep the sole surface and outside wall hard and dry, and counteract the softening you get from excessive moisture-laden environments.
"You are doing entirely different things to those two surfaces," Marcella reiterates. "One you want to soften, keep moist, and allow to grow. The other you want to make rock hard and dry so it can bear more weight."
Marcella said that softening the upper part of the hoof and drying and toughening the bearing surface of the hoof have been parts of standard clinical practice for a long time.
In conclusion, if your horse has or shows signs of having thin, shelly feet, the problem usually originates from one or more factors--poor environment, nutrition problems, underlying medical problems, genetics, and/or quality of hoof care. Explore these potential causes and involve your farrier and veterinarian early to resolve any problems.
About the Author
Genie Stewart-Spears resides with her husband on Runamuck Ranch in southern Illinois, in the Shawnee National Forest. Now a pleasure rider, she competed in endurance for 10 years and has served as the Media Chairperson for the American Endurance Ride Conference. Her photography and articles appear in several equine magazines and many books, brochures, and advertisements.