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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. |
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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. |
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Exposure:
shavings or sawdust from walnut trees is occasionally used
as animal bedding. Horses are most at risk. |
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Toxic principle:
unknown. A compound known as juglone has been suspected
to be the toxin, but efforts to document this have been inconclusive. |
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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.
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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.
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