We lived for almost 25 years on property that was loaded with Black Walnut
trees. There never seemed to be a problem until one gelding ate a load of
walnuts that fell from the tree above his corral and filled his corral. He was
sick, the vet came out and tubed him, and he was fine in a few days. I had to
always rake his corral during the season the walnuts dropped. However, I had an
older mare who I am sure foundered as a result of those trees. She only had an
oak tree in her corral and after several years in that corral I put her into a
larger one on the side of a hill that had a lot of black walnut trees. Other
horses had lived in that pen for years without any problems. But one
winter/spring was very wet and she stood in a lot of wet black walnut leaves and
foundered.
