I'm sorry to hear the baby didn't make it. The reason I asked what type of pasture you have is because I was worried about fescue toxicosis. (from a fungus that grows on fescue) It can cause prolonged gestation (as long as 13 to 14 months), foaling difficulties, thickened placentas (including “red bag” emergencies), and a decrease or complete absence of milk upon delivery.
Again, I'm very sorry to hear about the foal.
"Be a best friend, tell the truth, and overuse I love you
Go to work, do your best, don't outsmart your common sense
Never let your prayin knees get lazy
And love like crazy"