Is moldy hay or grain safe to feed to horses or cattle?

In the case of horses, the best practice is not to feed moldy hay or grain, ever. Since the horse does not have the same type of digestive system as a cow, what a cow may be able to eat without problem may make a horse colic.
For cattle, the answer depends on what mold, whether mycotoxins are present, which mycotoxins are present, at what level, what percent of the animal’s diet will be moldy grain, and what type of …