The American persimmon can be poisonous to horses. The problem is associated with tannins in the fruit. The tannins can precipitate from the fruit in the stomach and form a sticky mass. This mass can cause ulcers in the stomach and even lead to rupture of the stomach if the horse was to eat a large quantity of the fruit. This can also cause colic due to impaction in the stomach or the small intestine. Signs are colic and weight loss, but often they are sporadic and non-specific. This is a very difficult problem to diagnose but may be suspected in the fall if the horse has had access to the fruit. To prevent access to the fruit, keep the trees and horses separated.