I can only speak for what I've seen, which wasn't here in the US. I bought a former recipient mare, out of a university program herd. it's government- run, so rules in a private facility could be different.
There they live in a herd, large paddock, are being fed hay and a little grain, being handled daily, mostly by students. They lease the mares to the future foal owner, have no influence how the mare is treated there. Not all return.
They also have to cull every year, professor believes it's too risky once a mare is over 12, and if course the ones that didn't take. They are being sold to anybody who comes up with the equivalent of 400$.
The personnel is trying their best to find appropriate and loving homes, but can't always influence enough.
As I stated, that wasn't here, and not private.
I hope you'll find her a perfect home soon