If you’ve never seen a horse stricken by laminitis, consider yourself fortunate. This terrible disorder causes severe pain and potentially extensive damage to the horse’s feet. It’s a genuine medical emergency.
There are multiple possible causes of laminitis. One of the most familiar scenarios is ”horse got into the grain bin” (see sidebar, page 11). When there is a sudden increase in high-starch grain reaching the large intestine of the horse, the bacteria there ferment it rapidly, producing acidic conditions that can damage the lining of the bowel.
This allows absorption of bacterial toxins into the blood, as well as other bacterial products such as small proteins called vasoactive amines that can make the blood vessels in the feet spasm or clot.
Laminitis can also occur when mares have retained placenta or a bacterial infection gains access to the blood. Horses that have severe strangles, Potomac horse fever, Lyme disease, salmonella or damage to the intestinal tract from a severe colic may also develop laminitis.
Pasture-induced laminitis, which classically occurs in overweight ponies and horses, used to be blamed on ”rich grass,” but exactly what it was about the grass that caused the laminitis was unclear. Eating unlimited amounts of low-fiber, high-simple-carbohydrate young grasses can potentially lead to acidic colon, as with grain overload, but this doesn’t explain why some horses never have a problem with pasture and other horses can become laminitic even with extremely short grazing periods.
We now know that horses and ponies prone to pasture-induced laminitis are usually insulin-resistant. The details of how insulin resistance causes laminitis haven’t been determined, but we know that diets high in simple sugars or starches, like spring grass, worsen insulin resistance.
Corticosteroid drugs have laminitis on their list of side effects, probably because these drugs can cause insulin resistance. However, the risk of this occurring with corticosteroids is probably actually related to whether or not the horse is already insulin-resistant or not.
Symptoms Of Laminitis
Horses can get laminitis in all four feet, but it is typically much worse in the front feet because they carry more of the horse’s weight than the rear.
With a full-blown laminitis attack, the symptoms are almost unmistakable:
• The horse is rooted in place, usually with the front feet camped out in front of their normal position. Attempts to make the horse move are met with strong resistance, and the horse often will rock back onto his hindquarters.
• The horse may be sweating and/or blowing because of the pain.
• The feet will feel hot and the digital artery pulses are usually bounding. (Note: To locate the digital artery pulse, run your fingers lightly over the skin at the back of the fetlock joint. You will feel the artery rolling underneath the skin as you pass over it. Once the artery is located, press directly on it to feel the pulse. If you are unsure whether the temperature or pulse is elevated, compare to the hind feet.)
Only a few things are likely to be mistaken for a laminitis attack. One is tying-up, because of the pain, the horse’s refusal to move and the tense hindquarters. However, tying-up usually is triggered by exercise.
A horse with colic will also sometimes assume the camped-out stance typical with laminitis, show the same obvious pain and may also be reluctant to move. However, the horse with colic will almost always be looking back at its flank.
Severe hoof pain, such as abscesses, can look like laminitis. It would be unusual, though, for abscesses to occur in both front feet at the same time.
Regardless of whether the diagnosis is clear or not, any horse showing these symptoms needs to be seen by your veterinarian immediately.
Ice is always indicated with acute laminitis. If the horse can’t or won’t lift his legs to be put into ice soaks, you can pack finely crushed ice into self-sealing quart-size plastic bags and secure the bags to the pastern and front of the feet with a polo bandage or Vetrap. Ice will help control the inflammation and swelling with the feet and decreases pain.
Getting the horse’s feet up on a more yielding surface than the hard ground also helps. Precut styrofoam support pads are available from EDSS, Inc. (www.hopeforsoundness.com, 719-372-7463). It’s a good idea to keep a pair with your barn first-aid supplies, as they’re relatively inexpensive at about $11/pair. The relief after applying these pads is usually immediate and obvious. Pads can also be fashioned from high-density construction styrofoam, available at home improvement stores.
However, relieving the pain is only part of the equation. If the laminae become weak enough, they can separate. This allows the coffin bone (P3 = third phalanx) to become displaced in the hoof. A change in the position of the coffin bone relative to the edge of the hoof wall is called rotation.
Rotation can be of two types, capsular or bony. In capsular rotation, P3 and the bones above it stay in good alignment, but the hoof wall spreads away from the bone. In bony rotation, the P3 is both farther away from the hoof wall and also out of alignment with the bones above it. In sinking, the entire bone column drops within the hoof capsule and will be sitting closer to the ground than normal.
In all of those scenarios, there’s internal pressure on the live tissues within the sole from the weight of the horse coming down through the bones. This causes pain and, if severe enough, can damage or even shut off the blood supply to the sole.
When rotation or sinking is severe enough, the rim of the coffin bone may penetrate the sole. The force of the horse’s weight also can cause mechanical tearing of the damaged laminar connections.
This is why laminitic horses should not be forced to move and should be confined to a small area where they can lie down comfortably to get the weight off their damaged feet. Keeping them still is also particularly important if they are given pain-relieving medications.
The Vet Visit
When your vet arrives, he or she will likely give your horse an intravenous (IV) anti-inflammatory, like phenylbutazone (bute) or flunixin (Banamine). Many vets also use IV DMSO. You will be given a supply of anti-inflammatory to use orally at least for the next three to five days.
Many veterinatians also recommend acepr omazine is given every few hours, to help keep the blood vessels dilated. Others recommend isosoxuprine, although research in horses has shown variable oral absorption and no effect on the blood flow in the feet???at least in normal horses (laminitic horses have not been studied).
If the laminitis is related to over-eating, a stomach tube will be passed and the horse will be treated orally.
An important part of the visit will be radiographs/X-rays of the feet. Lateral radiographs allow your vet to see where the coffin bone is sitting in relation to the hoof wall and the ground. Horses with significant pressure on the sole have a more guarded prognosis overall.
Veterinarians vary in their opinion with regard to trimming laminitic horses. Some pull shoes and trim immediately. Others prefer not to stress the feet by making the horse stand on one leg while the other is being trimmed (when available, a sling can be used to solve that problem). Others prefer to wait a few days to let the acute inflammation settle down. This also gives the vet a chance to study the radiographs if digital X-ray capacity is not available.
The issue of how soon to trim is best handled on an individual basis. If the horse has severe trim problems that will mechanically stress the laminae, it’s sometimes best to trim right away. This would include horses with very high heels that force the coffin bone onto its tip, or those with feet that have grown long toes and a hoof capsule that is forward of where it should be (long toe, underslung heel syndrome). In the long-toed horses, the hoof wall tends to flare away from the white line and tug on the laminae, even in a normal foot.
Your vet will give you a supply of the recommended drugs. You’ll also want to stock up on styrofoam. Horses do eventually crush these pads down, and they will need to be reapplied. If your horse still needs to be trimmed, set up a time when your farrier and vet can both be there, in case the horse needs nerve blocks to be able to stand comfortably. Use of a cushiony foam, like memory foam, makes it easier for the horse to stand for trimming.
If the budget will allow, repeat X-rays before every trim. They’ll be essential if the horse worsens. The position of the coffin bone can change rapidly in a laminitic horse. The usual landmarks used for trimming are not reliable. Trims should be done every three to four weeks, minimally. Inflamed feet grow rapidly. If there is a major trim problem that also has to be resolved, trimming more frequently is advisable.
If the horse has poor-quality hoof horn and has been shod, shoes may need to be continued to keep the hoofwall from flaring away from the foot too badly, although Hoof Casts (see Horse Journal, October 2008) can accomplish this, too. For most horses, leaving shoes off is preferable since it makes frequent trimming easier and less traumatic for the horse. Styrofoam or boots with pads can be used to protect the feet.
If the horse is overweight, or the laminitis is suspected or known to be related to insulin resistance, diet control is important. Being overweight greatly increases the stresses put on the laminae. A horse with insulin-resistance-related laminitis is not going to improve until the diet is brought under control.
However, you should not starve the horse or deliberately feed poor-quality hay. Underfeeding only worsens insulin resistance and an inadequate diet robs the horse of protein, vitamins and minerals that are needed to heal the feet. With insulin resistance, the hay should be tested by a forage laboratory to determine the sugar and starch content. It should be under 10%, sugar and starch added together, for an insulin-resistant horse. If above this, the hay should be soaked before feeding. Ideally, the mineral profile of the hay should also be balanced according to the hay analysis (see ”Killing With Kindness,” January 2009). Feed the horse at a rate of 1.5% of current bodyweight or 2% of ideal bodyweight, whichever is larger, as a starting point.
If the cause of the laminitis has been found and correctly addressed, the acute inflammation will leave the feet usually in three to five days. The feet will cool off and the horse will be more willing to walk around. Exactly how much improvement you see depends on the extent of the damage. Mild cases with no change in the coffin bone position can be dramatically better in this time frame. Those with actual damage to the laminae and change in coffin bone position will take more time.
Nursing a horse back to soundness after laminitis is a long-term commitment to care. It will take at least one complete hoof growth cycle to realign the coffin bone. During this time, hoof care must be meticulously maintained and any diet adjustments needed followed faithfully. Failing to get and maintain a correct trim can quickly lead to hoof deformities and chronic laminitic pain (we have an upcoming article on chronic laminitis care).
With correct hoof care and general management, the long-term prognosis for return to comfort is quite good for most horses. Even horses that have sloughed their entire hoof wall or penetrated the sole can become at least pasture sound. If damage isn’t too severe and good hoof care is maintained, many have returned to full athletic use.
The prognosis is worst for horses with severe damage to the circulation to the sole. Some of these horses may not be saved except by radical surgery. How much pain the horse shows also depends to some extent on individual pain tolerance. Horses tend to be in severe pain when it doesn’t improve in the usual time frame.
The best diagnostic tool to evaluate circulation is a venogram done by a veterinarian who is very familiar with that technique. Dye is injected into the major vein of the foot, forced into the circulatory system and an X-ray is taken. Areas where blood flow is cut off are clearly seen.
Article by Eleanor Kellon, VMD, our Veterinary Editor. With her husband, she breeds, races and trains Standardbred harness horses in Pennsylvania.