January 2012

Laminitis

What is it?

Laminitis is the result of a disruption of blood flow to the sensitive and insensitive laminae of the equine hoof.  Whether the disruption of blood flow is intermittent, constant, or short term, there is a painful inflammatory response that can affect any or all of the hooves, but most commonly the front feet.

The laminae attach the coffin bone to the hoof wall.  As inflammation occurs, there is a painful separation that begins between these two structures.  These changes result in abnormal hoof growth, lameness, and (if severe) can progress to coffin bone rotation or sinking through the sole.

The term "founder" is often used interchangeably with laminitis. 

What causes it?

The definitive cause is unknown, but predisposing factors include:

• Grain overload (excessive carbohydrates).
• Exposure to lush pasture without time to adapt (grass founder).
• Illness with high fever.
• Severe colic or diarrhea (release of endotoxins).
• Retained placenta post foaling.
• Excessive walking/moving on road surfaces (road founder).
• Injury to another leg resulting in extra weightbearing to the normal hoof.
• Prolonged usage of corticosteroids.
• Bedding with black walnut shavings.
• Various primary foot diseases.
• Equine Cushing's disease

Are there other risk factors?

In addition to previous episodes of laminitis, other factors that increase the potential to develop laminitis include:

• Heavy breed horses, such as draft horses.
• Ponies, Morgans, donkeys.
• Overweight horses, especially with evidence of cresty neck.
• High nutritional plane (excessive carbohydrates).
• Unrestricted grain binges.
• Horses with metabolic syndrome.

What are some of the symptoms?

In acute cases:

• Lameness with shifting of weight between legs while standing.
• Increased digital pulses and heat felt around the coronary band.
• Pain upon manipulation of the hoof, especially with hoof tester on sole to toe.
• Hesitant gate, appears to "walk on eggshells".
• "Sawhorse" stance, with front legs stretched out front in attempts to decrease pressure on toes.
• Signs can appear as short as 8-12 hours after exposure to black walnut shavings, or 30-40 hours after a carbohydrate overload.

In chronic cases:

• Displacement of the coffin bone has already taken place.
• Dropped soles, flat feet.
• Rings along the hoof wall widen from toe to heel.
• Increased width of white line at the quarters and toes in the affected hoof.  Within the white line there can be evidence of seromas and abscesses.
• Dished hooves, due to unequal growth. (Aladdin slippers).

How is laminitis treated?

The sooner action is taken to stop the insult, the better the prognosis and recovery. The ultimate goal is to relieve pain and get the hooves to a functionally normal state.  Each laminitic case is unique to that horse and your veterinarian can diagnose and develop a treatment plan best suited for your horse.  Key steps may include:

• Diagnose and treat the primary problem (if laminitis is a secondary problem).
• Encourage resting and relieving pressure on the hoof/hooves. Stalling with supportive bedding (deep sawdust/sand).
• Dietary restrictions: Initially feed only hay until told otherwise.
• Mineral oil via nasogastric tube: Helps eliminate excessive grain in the GI tract, and decrease absorption of toxins.
• Administer fluids if ill or dehydrated.
• Non-steroidal anti-inflammatories to aid in pain control and decrease inflammation.
• Antibiotics and anti-toxins may be administered depending upon the situation.
• Open and drain any abscesses that develop.
• Work with farrier for corrective shoeing.

What is the prognosis?

The prognosis for laminitis varies.  Radiographs are essential in determining the degree of rotation of the coffin bone as it loses structural support from the laminae on the wall.  Once a laminitis event occurs, the horse is prone to future episodes, therefore prophylactic management measures are highly recommended. These include diet changes, regular hoof maintenance and routine health monitoring.  The sooner laminitis is diagnosed and treated, the better the long term prognosis.