You have to find a site or an advisor who can tell you what the real impact of all plants on horses is. I say that because there are so many products and plants that exist .... And above all it all depends on what you expect as result for the cure !!
In basic food, I like to use a cure made of garlic (petal) and roasted seeds of linen. It is simple not too aggressive and it works well :). Afterwards to make a good complement (and change the taste) I mix garlic and flax with apple and honey moment.
I hope this helps,