Black walnuts are large, 60-80 foot, forest trees native to much of North America. Wood shavings of black walnut have dependably caused founder in horses. As little as 5% black walnut in the shavings can induce laminitis. This article discusses identification, symptoms, cause of the laminitis, treatment, and prevention.

Black walnuts are large, 60-80 foot, forest trees native to much of North America. The dark bark has characteristic broad, round ridges. The leaves are alternate, pinnately compound, 1 to 2 feet long, with 13 to 23 sharply toothed, tapered-pointed leaflets. Often there is no terminal leaflet. The fruit is a very rough nut enclosed within a clammy glandular husk, 2 to 4 inches in diameter.