Our old TB mare still has heat cycles and she is 28 now. Old huzzy lol .
Alfalfa pellets and rice bran should help. Our TB's are hard keepers. Take lots of food even when they were younger.
She is looking better, and some stay kinda of ribby but not skinny.
Also, I have a question, is she lame on that knee? I noticed the bump in one of the pics. Hope she stays useable .