Just a word of caution:
Please get the vet out to examine her. Not only to get some input on the best approach to feed her but, she may be in foal
I read more often than not about rescued mares ending up putting a baby on the ground and nobody from her past knows how that happened.
A lady, I am forum acquainted with, bought a drop-dead gorgeous mare off C/L that the owners claimed could not get in foal.
She is in Canada, the horse was actually not too far from me.
It was this past April or May she had the mare shipped to her. That foal the mare couldn't conceive is just now old enough to be weaned
The Sellers claim they had no idea how the mare got preggars. They insisted they "only' had her in a pasture with a stud that was six months old, therefore couldn't possibly have gotten her "in the family way".
Here's a news flash --- if those testicles are dropped, that colt can produce babies.
So please, as a heads up for your own self, have a vet check your mare to see if she's possibly in foal because that will completely change her rehab diet
Good luck to you