In a perfect world, yes. The Black Walnut Tree secretes a toxic substance Juglone from its roots and has a lower level of the toxic substance in the bark, leaves, and nuts. The toxic substance has been well demonstrated to cause laminitis in horses, but this is most commonly reported when using Black Walnut wood shavings as bedding.
Although the toxin is obviously present in the living tree, the reported incidence of laminitis from being pastured with black walnut is much lower. In summary, the highest risk of black walnut toxicity is from bedding composed of black walnut shavings or sawdust. There is concern that ingestion of black walnut nuts/rinds, leaves and bark are a risk factor as well, though this is not highly reported.