Chronic Laminitis

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Normally, if a horse develops laminitis as a result of a one-time overload, such as over-eating grain, the acute inflammatory response will abate within three to five days, and the pain decreases steadily from that point (see acute laminitis, March 2009). However, some horses never stop hurting and are a challenge to treat.

Successful treatment for these chronic cases involves figuring out what’s really causing the pain, which we’ll discuss here.

It may be that the laminitis trigger hasn’t been eliminated. In these cases, the underlying cause is still there, so the laminitis itself is ongoing. Causes include incompletely controlled insulin resistance, undiagnosed or untreated Cushing’s disease, and Lyme disease. Laminitis pain in a horse with Lyme disease may be severe and out of proportion to the level of insulin resistance found on their blood tests. Laboratory work can check for these.

This pony is a good example of how X-rays may not match pain level. Despite the sinking, rotation and coffin bone remodeling, he’s pasture sound and even trots. Horses with ???winter laminitis??? become lame when the cold causes the blood supply to the feet to be restricted.

This pony is a good example of how X-rays may not match pain level. Despite the sinking, rotation and coffin bone remodeling, he’s pasture sound and even trots. Horses with ???winter laminitis??? become lame when the cold causes the blood supply to the feet to be restricted.

You could be dealing with Mechanical pain. A variety of options are available for laminitic horses, from the barefoot approach to intricate shoeing systems. What is ideal for one horse might not be for another.

Regardless of what is put on/under the feet, all methods agree on few key aspects:

• The bottom of the coffin bone should be from within 0 to 5 degrees of parallel with the sole.

• Wall flares must be removed to avoid traction on the laminae.

• Breakover at the toe should be eased and moved back as dictated by the location of the rim of the coffin bone.

Some horses will be most comfortable bearing most of the weight on their soles, others can’t tolerate sole pressure or must at least have the area corresponding to the rim of the coffin bone unloaded.

The degree of changes seen on radiographs doesn’t necessarily correlate with the amount of pain the horse seems to feel (see photo). Several studies have confirmed that horses with relatively normal appearing X-rays may have significant pain while those with extensive changes may be comfortable.

The horse may have unresolved abscesses.A fairly common cause of ongoing foot pain is pressure from abscess collections. Laminitis often causes bleeding under the hoof capsule.

Areas where laminae have been destroyed trigger an inflammatory response and there may be pockets of serum in the hoof. These may be uninfected collections or bacteria may gain access to them through even microscopic weaknesses in the white line.

Abscesses find their way out of the hoof by following a trail created by inflammation. Because inflammation and tissue breakdown are necessary parts of the abscess drainage process, horses kept on phenylbutazone for prolonged periods of time can have prolonged pain from unresolved abscess collections.

Some characteristics of abscess pain are that it:

• Returns or worsens two weeks or longer after the initial laminitis episode.

• Is often more severe than with the initial laminitis episode.

• Responds poorly to the usual anti-inflammatory medications.

• Is much worse in one foot, or involves only one foot.

• Appears shortly following a trim (changes the forces within the feet, which can make abscesses leak internally and trigger inflammation).

Tissue Damage. Research has shown that horses with laminitis can have changes to the nerves in their feet that would cause chronic pain (neuropathic pain). A similar problem has been described in people with insulin resistance or diabetes.

We’ve followed the progress of several horses supplemented with acetyl-L-carnitine (ALCar),a nutrient used to help alleviate the pain and encourage healing in humans with neuropathic pain (available through sources like Bulk Nutrition, www.bulknutrition.com, 800-975-8125, $24.99/500 grams).

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Since the supplement will only help horses with neuropathic pain, and there’s no way to diagnose with certainty that nerve changes are the reason an individual horse has ongoing pain, selecting candidates is a bit difficult. However, in our test horses we ruled out metabolic issues and mechanical factors before trying the supplement. All the horses had ongoing pain of from several months to several years duration and hadn’t responded, or only partially responded, to Gynostemma (below).

Approximately 85% have responded to the ALCar at a dose of 1 gram per 100 pounds of bodyweight.

L-carnitine and acetyl-L-carnitine are both found naturally in the horse’s blood stream and muscles. The supplement has been fed to horses entering a training program at the same dosage listed above.

Winter Laminitis.Laminitis can also result in damage to blood vessels in the feet. In many forms of laminitis, spasm in the small veins in the feet and activation of clotting have been documented. This can lead to the formation of clots that block circulation and contribute to tissue death. Inflammation alone can and does impair circulation because of swelling, again leading to tissue loss. Areas of damaged circulation can be repaired by regrowth of blood vessels, but it’s slow.

Damage to the circulation caused by laminitis may be behind a fairly common form of chronic laminitis pain — winter laminitis.

These horses typically have a past history of laminitis from which they have recovered and are sound in the warmer times of the year, but the arrival of cold weather triggers the pain.

Cold temperatures normally cause the blood supply to the feet and lower legs to be restricted. In normal horses, this doesn’t cause a problem, but in horses with compromised circulation it most certainly can. Keeping the horse warm with a blanket, if necessary, wrapping the lower legs (fleece-lined shipping boots and neoprene wrpas are good), and using hoof boots with a warm liner in the bottom help.

Also, winter pain in horses with previous laminitis, and many cases of chronic laminitis pain in general, often is alleviated by the herb Gynostemma pentaphyllum (available through Herbalcom, www.herbalcom.com, 888-649-3931, $13.99/lb.), a treatment that was first introduced here in Horse Journal.

This herb has the ability to stimulate the production of nitric oxide inside blood vessels, causing them to dilate. This is the same mechanism of action as nitroglycerin. The dose is ?? to 2 teaspoons, twice a day. It works best when given 15 minutes before feeding.

Most horses enjoy the mild taste and will lick it up as a paste from a bowl. The correct dose has been reached when the gums and tongue turn a rosier pink color.

For stubborn cases, AAKG (arginine alphaketoglutarate) can be also be given (available through Bulk Nutrition, www.bulknutrition.com, 800-975-8125, $6.99/90 grams). This is a source of the amino acid arginine, which is used to manufacture nitric oxide. The starting dose is 3 grams.

AAKG can be found in several body-building supplements for humans. An inexpensive one is NOS, sold at Walmart. Caution: Nitric oxide is also generated in large amounts as part of the inflammatory process. AAKG will also ”feed” inflammation. It therefore should never to be given to horses suspected of having active laminitis, or to horses with active infection.

Article by Dr. Eleanor Kellon, our Veterinary Editor.