It is well established that horses bedded on wood shavings that contain black walnut shavings can develop laminitis. In fact, horses will show signs of toxicity manifested as laminitis (founder) when they are exposed to as little as 5 - 20% of black walnut shavings in their bedding. The toxic substance is known as juglone and is absorbed through the soles of the horse’s feet.

In a pasture situation, it is not clearly defined what the level of risk factors, if any may be associated with horses standing under, walking in leaves and/or grazing around black walnut trees. However, there are several management practices that you may consider to minimize potential exposure which include: 1) fence around the tree to limit access and keep horses from standing on any exposed roots or chewing on bark, 2) remove fallen walnuts from the area as fallen walnuts may become moldy and may also contain a fungal toxin, 3) prune branches horses can reach as well as remove any fallen branches from the pasture and 4) in periods of limited forage availability and/or leaf drop, such as in the fall remove horses from the area, if need be.

Black walnut is also not advised for goats and these practices may also help mitigate any risk to goats.

One additional consideration, if pasture shade is limited, consider how the tree can still be useful for shade by analyzing where shade is projected from the tree throughout the day and fence around it accordingly in a way that allows horses to move around the fenced in tree and still utilize the shade. If a decision is made to remove the tree, it is important to remove all shavings associated with the tree removal.

A place to start would be contacting a local tree removal company and inquire through any networks they may have in regard to the potential value of the tree.