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Black Walnut Toxicosis in Horses: Fact or Fiction By Kentucky Equine Research Staff · March 25, 2014

It’s a fact! Black walnut toxicosis or black walnut poisoning is an imminent threat to horses bedded on shavings, sawdust, or other salvage derived from black walnut trees.

The threat is serious, as laminitis and colic are likely outcomes.

Don’t get the wrong idea, though: horses do not necessarily have to ingest these materials to become foundered or colicky. They only have to stand on remnants from black walnut trees.  In fact, horses have developed laminitis when only 5 to 20% of the bedding mixture was obtained from black walnut trees.

Consumption of black walnut shavings can also induce laminitis and abdominal pain.

Bedding from other trees in the walnut family might trigger similar problems for horses. Shavings or sawdust gathered from nearby lumberyards or wood-processing facilities, such as furniture factories, where trees of various species are processed should be scrutinized closely for black walnut debris.

Researchers believe that a toxin in black walnut shavings is absorbed through the coronary band and skin, causing alterations in normal blood flow to the hoof and leading to typical signs of laminitis, including pounding digital pulse, unwillingness to move, extreme lameness, depression, limb edema, and increased heart and respiratory rate.

Like all cases of suspected laminitis, a veterinarian should be consulted immediately. Diagnostic tests, including radiography, will likely be performed, and a treatment plan will be established. Prognosis depends largely on length of exposure and speed of treatment.