Horse News & Views - August 2005

Ministry of Agriculture, Food and Rural Affairs

Ontario Association of Equine Practitioners

• Black walnut (Juglans nigra) is a tree native to southwestern Ontario and the eastern United States. Occasionally, black walnut shavings will be incorporated into horse bedding. Horses bedded on black walnut shavings will become acutely lame within 12 to 24 hours; exhibit moderate to severe lameness at the walk and refuse to pick up their feet. In their stall, they commonly assume a sawhorse stance.

  Researchers can consistently reproduce the syndrome by preparing an extract of heartwood shavings and administering it by nasogastric tube. Applying the extract to the hoofs, however, does not reproduce the syndrome. The aqueous extract of heartwood does not contain juglone. Therefore, researchers believe that there is another active ingredient in black walnut that is responsible for causing laminitis. (Ref. Minnick PD, Brown CM, Braselton WE, Meerdink GL, Slanker MR. The induction of equine laminitis with an aqueous extract of the heartwood of black walnut (Juglans nigra). Vet Hum Toxicol 1987; 29 (3, June): 230-233.)

  Horse owners should ensure that the shavings they are purchasing are not contaminated with black walnut shavings, either in the fresh or kiln-dried form.

• Hay and pasture fields, which suffered the severe drought this summer, will go into the winter and survive better if commercial fertilizer is applied in the late summer and/or early fall. Alfalfa, in particular, will have less winterkill if phosphorus and potassium fertilizers are applied. Consult your local fertilizer suppliers for fertilizer and application-rate recommendations.

   

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