Hoof care is one of the most important aspects of quality horse management. Hoof trimming, shoeing if necessary, good nutrition to ensure good hoof growth, and inspection for disease or injury to the foot are just a few of the tasks a horse owner needs to worry about. Yet no matter how much attention is paid to these steps, if your horse's feet are constantly wet, this can create a disastrous situation for proper hoof health.
A Product of His Environment
Water is nature's hoof moisturizer, but moderation is key. Too much moisture can lead to deformed hooves because as the hoof becomes softer, it loses its structural integrity. Prolonged and excessive environmental moisture leads to dangerously high hoof moisture levels.
To better understand hooves getting saturated, Stephen O'Grady, DVM, MRCVS, owner of the Northern Virginia Equine practice in Marshall, Va., gives the analogy of water's effects on a board: "If you pour water over a board, the water will run off the board. But if you tie a rock to the board and submerge it in a water trough, the board will become saturated, become soft, and eventually fall apart.
"The horse is a product of his environment, and if he lives in a dry area, he's going to have dry feet. But if he lives in a moist area, he's going to have softer feet," he adds. "A horse from Florida does not have the same cup in the bottom of the foot as a horse in the North." This is due to softer hoof walls from excessive humidity coupled with the sandy soil (the primary type of footing); this combination causes the sole of the foot to flatten.
"The wild ponies on Chincoteague Island in Virginia live in a swamp environment and have horrible-looking flat feet," says O'Grady. "They live in an area with no counterpressure (the force that hooves receives that helps make them stronger, such as standing on a hard surface) and are always taking up excessive moisture in their feet. The wild ponies' hooves are so saturated with water that they have little structural integrity."
This isn't a problem for the ponies because they aren't ridden and walk on soft, wet ground all the time, but when a domestic horse with wet feet is expected to be ridden on firmer surfaces, he is going to encounter problems with soft hoof walls that become increasingly weak, and possibly lameness as a result of the foot not being able to provide adequate support for his and his rider's body weight.
"Stabled horse's feet are often continually wet," says O'Grady. "One of the worst problems that we encounter is the show horses that compete in multiple divisions. First thing in the morning they get a bath, and each time they come out of the ring they get a bath. It just gets to the point that the entire structure on the bottom of the limb gets saturated. The only way to get around this is to not give the horses baths all the time."
Sponging off horses instead of hosing them down is one way we can keep their feet from getting completely soaked. (This also helps avoid or minimize the hose area mud bog if the wash area is outside!)
Anatomy and Moisture Levels
The horse's hoof is naturally designed to hold a certain level of moisture to keep it strong, healthy, and supportive of the horse's body weight. Rigid and closely packed horn tubules aligned in a roughly vertical and parallel arrangement in the hoof wall retain moisture--similar to a sponge holding water. However, when the hoof capsule is saturated with water, the horn becomes swollen and more flexible, thus reducing its natural strength (think of your own fingernails that become soft after washing dishes or bathing).
"The hoof wall is made of proteins," notes O'Grady. "It is porous, and moisture can be absorbed though the outer hoof wall over time. It doesn't derive the moisture necessary for good hoof health from the outside, but the hoof can absorb moisture from the environment to the point where the moisture in the horn is excessive."
Melinda Duer, MA, PhD, senior lecturer in chemistry at the University of Cambridge, studies the effects of moisture on hoof walls. She says, "Hooves seem to be strongest when there is no water between the coils (springs, or tubules) within the hoof," or when the hoof tubules are dry.
In the study, Duer took the outer layer of hoof horn in the toe region from a normal Caspian horse's hoof and ground it to a fine powder. The sample was examined and the nuclear magnetic resonance characteristics were recorded. The hoof powder was then dried out and examined again to compare differences between normal hoof wall, moist hoof wall, and dehydrated hoof wall.
Duer found that when the keratin in the hoof wall dried out, its chemical arrangement was altered. The keratin molecule chains comprising hoof tubules became less mobile and more rigid (the hoof wall becomes harder and stronger).
Yet her research also pointed out places in the keratin molecule where water can attach and break the hydrogen bonds that hold the hoof tubules together. When hoof horn absorbs water and swells, the normal keratin molecular structure is disrupted to accommodate the newly introduced water molecules. This causes the chemical and electrical bonds between adjoining keratin molecules to stretch and swell to let in the water molecules. The stretching causes the bonds to weaken, thus weakening the hoof structure and compromising the hoof's shock-absorbing abilities.
It is believed that the degree to which your horse will experience problems with excessive moisture is based on his genes. "A horse's foot that is affected most by moisture is a foot that is already genetically weak," says O'Grady. Yet the exact genetics of how or why the horse is predisposed to hoof problems is currently unknown.
It is important to remember that every horse is an individual, and the way a hoof is able to deal with the environment will be different from horse to horse. "You can take horse A stabled in filth, and take horse B stabled in filth," explains O'Grady. "Horse A can come out with healthy hooves, and horse B can come out with thrush, hoof wall separations, white line disease, and hoof cracks. The horse has to have a predisposition to hoof problems."
Thoroughbred show horses and racehorses seem most prone to having excessive moisture lead to softer feet. "With the experience of being a farrier for all these years, a Thoroughbred horse's feet, who generally has the least amount of mass or strength in his foot than other breeds, is going to suffer the most from excessive moisture," remarks O'Grady.
Unfortunately, appearances can be deceiving. When hooves are wet and swollen, the cracks close up, the hoof is shinier, and it appears to be healthier. But as time goes on, water-sodden hooves will begin to show cracks and be more likely to lose shoes because the horn is weak and cannot hold the nails. "The foot just gets overwhelmed with moisture to the point where the clinches start to pop up, and the wall just doesn't have the thickness, the firmness, or the strength it needs because it has been softened," says O'Grady.
Hooves are naturally porous, but when they are already of poor quality and become sodden, they can be even more prone to disease as the horn becomes more permeable to microorganisms, including bacteria and fungi, says Susan Kempson, BSc, PhD, senior lecturer in preclinical veterinary science in the Royal (Dick) School of Veterinary Studies at the University of Edinbrugh.
"The sole is the most permeable of the horn tissues and is most affected by bacterial and fungal infections," she says. "Poor-quality hooves are more permeable than good-quality hooves. Hoof cracks, chipped areas, and horseshoe nails create a route and environment conducive to fungal or bacterial growth. Greasy hoof dressings seal in these fungi and microorganisms and create the anaerobic (lacking oxygen) environment needed for their proliferation. Microorganisms, fungi, and yeast are found on healthy hooves and as opportunists, take advantage of defects that provide the proper environment for proliferation."
O'Grady agrees that hoof dressings serve little purpose in maintaining healthy hooves. "The blood supply, or circulation to the foot that affects the dermal structures of the foot, comes from the inside," he explains. "All the sealants that you put on the horse's hoof to keep them 'healthy' are probably of little value. The hoof oil gets washed off, just like anything else. And if you put oil on to the point where it accumulates and you get a 'sludge' build-up, you can trap bacteria in the moist hoof," which can lead to infection.
Drying Out Wet Hooves
If you horse does suffer from overly moist feet, you have a few options to lessen the severity of the problem and make the most of your horse's genes.
O'Grady recommends horses with too much hoof moisture stand in bedding that is a wood product, such as shavings or sawdust, because of its drying properties. "Sawdust has the ability to draw out water. If a horse has an oily or wet foot, I'll just rub sawdust over it for a minute or two and the hoof will dry," offers O'Grady.
There is no need to worry about hooves getting overly dry. O'Grady notes, "I haven't seen it where horses living on sawdust get too-dry feet. It is pretty hard when you think of really soft feet that are collapsing (because of their weakness) that would dry out to the point to where they have structural damage from too little moisture.
"Even if a hoof is a little on the dry side, it is on the outside of the hoof capsule," adds O'Grady. "Towards the inside of the hoof, the tubules are wider and less dense. A crack from a dry hoof isn't going to go through to the inside and will just be on the surface." In other words, deeper cracks signify imbalance; dryness alone wouldn't cause them.
Wet hooves are worse than dry hooves, says O'Grady: "With wet or dry hooves, you're talking about the hoof capsule. The inner structures still have good circulation and are still working. It's the outer part that has the change in structure. Being soft from too much moisture, you're losing your structural integrity. A soft hoof has too much elasticity and too much flexibility. The foot no longer has the strength it should."
Stabling horses on wood products to dry hooves out, giving horses fewer baths, limiting hoof dressing usage, and keeping your horse in a clean and sanitary environment are all steps you can take to keep your horse's hooves as dry and as healthy as possible. And as always, consult with your veterinarian and farrier to make sure you are providing proper management for your horse to ensure good hoof health.
About the Author
Marcella Reca Zipp, M.S., is a former staff writer for The Horse. She is completing her doctorate in Environmental Education and researching adolescent relationships with horses and nature. She lives with her family, senior horse, and flock of chickens on an island in the Chain O'Lakes.
POLL: Radiographs for Hoof Care