Makes me glad I have a chestnut now...hahaha...but then, I didn't really care either way, even when I had my bays... I just hate spending so much on different supplements! Haha!
I would try sheeting her...that is the simplest, and you won't test pos. On drug tests.
Oh, and just make sure she is getting adequate levels of copper; being a dark colored horse, she requires more than other lighter colored horses...most people forget that, and it's a simple thing to ensure some 'color protection'!
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."