Black Walnut Toxicosis in Horses

Black walnut toxicosis is rare in horses, due to owner awareness about the toxicosis. Black walnut trees are found throughout the eastern United States, but due to the popularity of the wood for lumbering, shavings can be found anywhere in the world. Contact with black walnut shavings can cause a potentially life-threatening condition and must be treated as an emergency.

Prompt treatment and prevention are paramount in ensuring the animals well being.

Horses that ingest leaves or pollen develop the following symptoms:

• Abdominal pain
• Respiratory difficulties

Laminitis can also result in a "sawhorse" or "camped out" stance, which is when the front limbs extend forwards while the horse shifts their weight backward.

Black walnut toxicosis occurs when a horse comes into contact with black walnut shavings or ingests the black walnut tree's bark, pollen, or leaves.

Horses bedded on shavings containing 5-20% black walnut wood can develop symptoms of black walnut toxicosis.

Diagnosis of laminitis is straightforward. A horse presenting symptoms of black walnut toxicosis generally undergoes the following diagnostics:

• Physical examination
• Diagnostic imaging, including X-rays of the feet
• Hoof examination or lameness examination
• Examination of the animal's bedding
• Testing of the bedding for black walnut in some cases

There is no specific antidote for black walnut toxicosis. Treatment is supportive and symptomatic and includes:

• Removal of contaminated bedding
• IV fluid therapy
• Washing the animal's legs to prevent further toxin exposure

Treatment options for horses diagnosed with black walnut-caused laminitis include:

• Pain medication (NSAIDs)
• Stall rest
• Cold water therapy or icing the hooves

Horses diagnosed with laminitis require long-term monitoring.

If the condition is treated in its early stages and the source of the toxin is promptly removed, prognosis is good, with most animals able to recover within days after the removal of contaminated bedding.

While black walnut toxicosis is not life-threatening on its own, laminitis is an emergency as it is among the leading causes of death in horses.

Horses that develop mild laminitis are typically able to return to pre-toxicosis activity levels once rehabilitated.

Hoses that are diagnosed with moderate laminitis are able to recover but are unlikely able to return to athletic activity.

Horses that develop severe lameness due to laminitis carry a guarded to poor prognosis and are often euthanized.

Black walnut toxicosis is not a contagious condition. The condition is entirely preventable by ensuring that horses do not enter into contact with any part of the black walnut tree; prevention strategies include:

• Avoid planting walnut trees in farms or paddocks
• Only buying bedding from trusted sources
• Analyzing bedding: if in doubt, contact a medical professional prior to using the bedding
• Eradicating or fencing off black walnut trees
• Promptly removing fallen black walnut leaves and branches

Black walnut is rare in horses due to owner awareness about the toxicosis.

Horses living in eastern US states and southern Ontario are more likely to come into contact with black walnut trees.

• Removal of contaminated bedding
• NSAIDs
• Washing the animal's legs
• Cold water baths