Are Black Walnut Wormers Safe for Horses?

Are Black Walnut Wormers Safe for Horses?


Can you please clear up the confusion over Black Walnut being poisonous to horses? I have read about the toxic properties of Black Walnut shavings when used as bedding for horses. Last week, I bought a herbal horse wormer in powder form. One of the ingredients is Black Walnut – Juglans nigra. Is this safe to use for horses? I phoned the supplier but they didn’t have any info. The woman on the phone said “we haven’t had any deaths so it must be safe, don’t worry”. Then she laughed and I felt most annoyed by her attitude.

Is the herbal horse wormer safe to use?

Vanessa H


No, the herbal horse wormer is not safe to use, bin it. Black Walnut in any form is toxic for horses.

You were quite right to be concerned about the herbal wormer containing Black Walnut. Black Walnut (Juglans Nigra) not to be confused with the European Walnut, is toxic for horses, resulting in laminitis. The Black Walnut grows across the United States from the North Eastern states to Texas. The wood is used in furniture manufacture and the shavings, as a by product for animal bedding. Horses bedded on shavings with only 5% Black Walnut were still affected by laminitis within 8 hours.

Laminitis occurs within 8 hours of giving either an aqueous extract or introducing the shavings as bedding. Other symptoms include; filling and pitting edema of the legs, increased heart rate, increased respiratory rate, a raised temperature and pounding digital pulses

Juglone, an alkaloid chemically similar to iodine, found in the hulls was once thought to be the cause. Trials in America have established that Juglone alone is not the sole cause. In fact, all parts of the Black Walnut tree are toxic for horses and will cause laminitis. Trials using aqueous extracts of the heartwood which contains no juglone were given, resulting in laminitis, raised hoof temperature and pounding digital pulses.

The results of these trials were reported in the American Veterinary Journal 1990:51:83-88 by Galey F D,Beasley V R, Schaeffer D, et al. ‘Effect of an aqueous extract of Black Walnut’.

Another study by Uhlinger C. ‘Black Walnut icosis in ten horses’ was reported in 1989 in the Journal of the American Veterinary Medical Association 1989:195: 343-344.

Click here to read more about worming your horse

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