Our horses are on fescue, and all of them are mares. However, if you have a bred mare, fescue can cause problems with a thickened placenta, no milk at foaling, and excessive bleeding. Out here, all you have is fescue, so the recommendation is to pull bred mares off fescue for the last part of gestation (the last 3 months) and dry lot them. Our first year out here we lost 3 foals because no one told us that fact. Clover can cause "slobbers" in horses; they drool excessively! Looks horrible but is painless. But that usually happens in a wet year and is actually caused by a mold that grows on the clover, or so my vet said! But, of course, that has not been a problem this year since we have had almost NO rain!!!
When we bought horse hay, we always looked for a good alfalfa grass mix to feed. Now that we have them on pasture, no need to buy hay! But with no rain, the grass is slim pickins' :yuck: