Equine laminitis is a painful condition affecting the horse’s hooves. Cases of laminitis range in severity from mild foot tenderness to chronic founder, potentially impeding the horse’s ability to walk and decreasing quality of life.

Laminitis is the bane of any horse owner’s existence. Horses affected by laminitis suffer excruciating pain as the soft hoof structures, known as laminae, become unstable.

While laminitis does not usually kill horses, per se, owners may make the decision to euthanize if the prognosis is poor or treatments do not work. 7% of equine deaths are associated with laminitis in some way. [1]

Fortunately, most horses will recover from laminitis to some degree, but it can take time. Once recovered, the horse could be more short-strided than before laminitis struck.

Laminitis is always an equine emergency. Call your vet immediately if your horse develops symptoms of this potentially life-altering condition. Prompt treatment can often prevent further damage when caught at an early stage.

The most important thing in any case of laminitis is to identify and remove the cause.

What is Equine Laminitis?

The term laminitis literally means inflammation of the hoof’s laminaebut not all types of laminitis actually have inflammation as a key feature. The laminae within the hoof keeps the coffin bone adhered to the hoof wall.

The coffin bone, also known as the distal phalanx or third phalanx, is totally encased within the hoof and provides attachment for the deep digital flexor tendon.

In laminitis, the laminae elongate and weaken then may start separating. Should separation occur, the coffin bone loses support and rotates side-to-side and/or downward. A rotated coffin bone puts focal pressure on the sole and its blood supply and nerves.

In the worst-case scenario, the coffin bone loses all laminar support. The coffin bone can sink and even rupture out the sole of the hoof. Recovery from penetration is possible but takes a prolonged course of intensive nursing.

 
Healthy vs Laminitic Horse Hoof

Although laminitis is a disease of the hoof, the events leading to laminar breakdown have their origins in the animal’s immune system, gastrointestinal tract, or endocrine system.

Once a horse develops laminitis, recurrence is possible. Careful management is key to preventing recurrence and keeping the horse as sound as possible.

Some horses will recover fully from a bout of laminitis, and others may prove serviceably sound for less demanding work. There are horses who never regain soundness after laminitis. In some equines, it becomes a chronic issue.

Signs and Symptoms of Acute Laminitis

Laminitis is a painful condition. If your horse exhibits reluctance to walk, is laying down frequently, “walks on eggshells”, or acts like they’re trying to shift weight off their forehand standing or turning tightly, you should suspect laminitis.

Although all four hooves can be affected, laminitis is more obvious in the front feet because they bear more of the horse’s weight.

Signs of laminitis include:

  • Heat in the hooves
  • Increased digital pulse
  • Sensitivity to hoof testers, particularly over the toe
  • Reluctance to move
  • Laying down more frequently
  • “Rocking back” or shifting weight off the forehand
  • Tentative walking on concrete or hard surfaces, particularly when turning tightly
  • Coronary softening
  • Rigid head carriage (either high or low) and loss of the normal swing to the back at the walk
  • Muscular tension in the shoulders, back and hindquarters

In the most severe cases, a bloody exudate may seep from the coronary band. The prognosis for equines who reach this point is poor.

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Chronic Laminitis

Horses with chronic laminitis sport telltale rings on the affected hooves. These rings correspond to abnormal hoof growth that occurs during laminitic episodes. They are usually wider at the heel than the toe.

There are horses who experience mild cases of laminitis that go undetected by caretakers, but the rings in the hoof will eventually appear if there is rotation.

With chronic laminitis, hoof walls may become dish-shaped and may display separation at the white line, referred to as seedy toe. If the coffin bone rotates, the sole will appear convex or bulges.

Horses with chronic laminitis are prone to frequent subsolar abscesses. Foot abscesses often occur in a single hoof, but you should always have your vet confirm your horses is indeed suffering from an abscess and not a recurrent episode of laminitis or other emergency.

Horses with undiagnosed and untreated metabolic syndrome will have internal changes in their feet but may not be suspected to be laminitic because they are not having an acutely painful episode. [5] In these cases, their first bout of “acute” laminitis is actually the culminating event of months or years of damage.

Founder vs. Laminitis

Laypeople often use the terms “laminitis” and “founder” interchangeably, but they are not synonymous. Founder occurs when the horse’s coffin bone has sunk or rotated, indicating a more severe or chronic case of laminitis.

Causes of Laminitis

There are three major types of laminitis:

Endocrinopathic laminitis

Endocrinopathic laminitis includes pasture-associated laminitis (“grass laminitis”), and represents 90% or more of cases. The cause of the abnormal lengthening and weakening of the laminae is high insulin. It has been established there is no inciting inflammatory response in this type of laminitis. [6]

Sepsis-associated laminitis

Sepsis-associated laminitis, which occurs in cases of severe systemic inflammation, is associated with serious illness and bacterial endotoxin production. Examples include salmonellosis, colic, bastard Strangles, Potomac Horse Fever, and retained placenta.

Laminitis caused by experimental fructan overload or the “horse got into the grain bin” scenario are also triggered by a systemic inflammatory response when bacterial byproducts gain access to the blood via a damaged gut wall.

Supporting limb laminitis

Support limb laminitis (SLL), the least common type of laminitis, occurs in horses suffering a non-weight-bearing lameness. Laminitis develops in the opposite supporting limb due to prolonged excessive weight-bearing. An example of SLL most people are familiar with is Kentucky Derby winner Barbaro, who was euthanized after developing laminitis in his supporting limb following surgery to repair his hindlimb fracture. [2]

Other scenarios that can trigger laminitis include: [3]

  • “Road founder” or excessive concussion on hard surfaces, more common in driving horses
  • Pregnancy-induced insulin resistance
  • Toxins entering the body, such as from a snake bite
  • Bedding on black walnut shavings. As little as 10% of black walnut residues in the bedding can result in laminitis. [4]
  • Ingestion of Hoary allysum plants on pasture or baled into hay
  • Tall fescue endophyte ingestion
  • Severe white line disease
  • High grade clubbed foot
  • Cephalosporin antibiotic use
  • Use of highly potent corticosteroids such as betamethasone may also predispose horses to laminitis by inducing insulin resistance

Risk Factors for Laminitis

While any equine may develop laminitis, some are more vulnerable than others. Risk factors for laminitis include:

Horses who have received high or long-term doses of corticosteroids are at increased risk of developing laminitis because these drugs induce insulin resistance. In particular, horses with pre-existing metabolic syndrome may develop laminitis with the use of any corticosteroid, including those administered by joint injection.

Animals with poor hoof or