Hot hooves, pounding digital pulses, a sawhorse stance, severe lameness; these are all signs of laminitis – one of the conditions most dreaded by horse owners, and for good reason! In severe cases, laminitis can result in permanent lameness and even lead to euthanasia.

Laminitis occurs when there is damage to the laminae of the hoof — where the hoof wall is connected to the coffin bone. It can occur in one or multiple hooves at the same time and by different mechanisms.

The separation can lead to permanent structural changes in the foot and lasting lameness. In rare cases, destabilization and rotation of the coffin bone can be so severe, the coffin bone actually ruptures through the sole of the hoof.

Researchers have learned that laminitis does not strike out of nowhere. Instead, there are often early warning signs and a prolonged subclinical phase that precede clinical laminitis. [1]

If you can learn to recognize these signs in your horse, then you greatly improve your chances of identifying and reversing this condition before it becomes severe and life-threatening.

How Laminitis Occurs

While laminitis was once considered to be a disease in and of itself, researchers now agree that it is a consequence associated with systemic conditions including endocrine disorders, sepsis or systemic inflammatory response syndrome (SIRS), toxins, and overloading of a hoof.

Laminitis associated with metabolic disease, also known as endocrinopathic laminitis is the most common presentation. Researchers believe that more than 90% of horses that develop laminitis have an underlying endocrine disease, that results in elevated insulin (hyperinsulinemia) usually Equine Metabolic Syndrome (EMS) or Cushing’s Disease. [2]

Specifically, insulin resistance and hyperinsulinemia alter blood flow mechanics to the foot. [2] These horses are more likely to suffer from laminitis if their diet is not properly controlled for less than 10% hydrolyzable carbohydrates (HC) (ESC + starch).

Pregnant mares become insulin resistant and may also develop laminitis even if they are not hyperinsulinemic when not pregnant. [10]

 

Healthy vs Laminitic Horse HoofIllustration:

 

Endocrinopathic Laminitis

When horses ingest a large quantity of carbohydrates (starches and sugars), carbohydrate metabolism causes a spike in blood insulin.

Horses with metabolic disease and insulin resistance already have high baseline insulin levels, which means this spike can be even more profound. The resulting insulin crisis can lead to sudden and dramatic impaired blood flow to the feet. [2]

Hindgut acidosis

When horses ingest a large quantity of starch from grains or an experimentally high dose of fructan, the small intestine becomes overwhelmed and fructan or undigested starches spill over into the hindgut.

Starch and fructan fermentation in the hindgut increases hindgut acidity resulting in a shift in the microbial population of the hindgut as beneficial bacterial colonies begin to die off.

Components of these dead microbes, known as endotoxins, can be absorbed into the bloodstream (endotoxemia) and trigger a systemic inflammatory response. [3]

Sepsis-induced laminitis

Severe illness and endotoxemia triggers systemic inflammation, resulting in sepsis or systemic inflammatory response syndrome (SIRS) which can trigger laminitis.

Examples include cases of:

Nutritional toxicity

Acute laminitis can occur due to high intake of certain heavy metals including mercury. [11]

Known plants capable of inducing laminitis are black walnut tree , Hoary Alyssum, Red Oak acorn or buds, and avocados. Rattlesnake venom may also induce laminitis. [12]

Supporting Limb Laminitis

Supporting limb laminitis describes the scenario in which a horse is non-weight-bearing in one limb, perhaps due to an injury, and overloads the opposite limb for a prolonged period of time.

Excessive weight-bearing in the support limb leads to structural breakdown of the laminae and coffin bone rotation.