Feed for a Thoroughbred?

Hi, i have a 12yr old TB mare who is losing weight due to my paddocks becoming bare with the winter. I am trying to come up with a feed plan for her that will be effective but not cost me a fortune as i don't really have the money to spend. So i am looking for things i could get for her that would condition her and help her keep weight on, and gain more weight. Any suggestions? Also if you could put amounts if feed needs to be made up so i know how many scoops, etc, etc. Thankyou :D