rodeoqueen77 - To be honest with you, your mare isn't well-built at all. And I don't have power over what you do, but I would strongly recommend not doing hard riding on her, like barrels or poles.
I work at a horse rescue, and we had an older horse come in that had a long back and wasn't well-rounded. He'd been ridden in his younger days, and guess what happened? He got extreme sway-back to the point where I hurt for him. And so many horses come into our rescue that have poor conformation because of careless breeding.
If you truly do have 43 horses on your ranch, why not ride or breed another horse? I'm sorry, but it's ignorant to have the foal suffer the same poor conformation and future back pain - just because you want a foal.
Just my honest opinion.
"A horse is the projection of peoples' dreams about themselves - strong, powerful, beautiful - and it has the capability of giving us escape from our mundane existence."