Something you might want to do is check out "FeedXL". It's a really great website where you can enter in what you're feeding and how much, and the website, using information you've entered about your horse+diet, will determine if she's getting everything she needs in her diet to be healthy. If she's not getting enough of something, there will often be suggestions of what might be needed in the diet - like loose salt or that sort of thing.
Of course, I sound like an ad for them now! haha But really, it's a super great investment and it's helped me so much with my mare's diet.
AND there's a half-off sale, with the code of "AFUSGT" going on right now! So a month's subscription, to the version that gets you the really "extra" stuff is only $10. I think the average, basic overview, one might be something like $5. Anyway, it's super affordable at that price and you might discover some stuff you didn't know! [not to mention that FeedXL is SUPER fun! haha *Nerd Alert!!*]
Fabio - 13 year old Arabian/Lipizzan gelding
Hazel - 14 year old Angora goat
Atticus - 4 year old LaMancha/Alpine cross goat
Rest peacefully, Lacey.