Juglans nigra

BLACK WALNUT

Description

Walnut trees are 50-100 meters tall and have dark, deeply furrowed bark, alternate pinnately compound leaves with approximately 20 leaflets and a spherical fruit 3-7 centimeters in diameter. A thick green husk breaks open to reveal a hard, brown, furrowed nut.

Geographic range

black walnut trees range widely throughout the eastern United States as far west as the Missouri river. They prefer the moist, rich soils of bottom lands.

Exposure

shavings or sawdust from walnut trees is occasionally used as animal bedding. Horses are most at risk.

Toxic principle

unknown. A compound known as juglone has been suspected to be the toxin, but efforts to document this have been inconclusive.

Diagnosis

Clinical signs

in horses occur within 24 hours of exposure to walnut shavings and include rapid onset of laminitis, a digital pulse, distal edema of the limbs, polypnea and elevated temperature. Necrosis of the dorsal laminae may occur and complicate recovery.

Laboratory diagnosis

microscopic examination of the bedding for the presence of walnut shaving confirms exposure.

Lesions

consistent with laminitis.

Treatment

• The source of the walnut should be removed, and gastrointestinal detoxification carried out using mineral oil or activated charcoal and a mild cathartic.
• The legs and feet should be washed.
• Phenylbutazone or acepromazine can be used to treat pain associated with laminitis.