Feeding the Active Senior Horse?

I have a 22 year old thoroughbred who is worked hard about 2-3 times a week. She is sound, but coming out of this Winter she has gotten a bit skinny. I want to change her feed. Should I put her on a Senior Feed or a Performance Feed? I was thinking a 14% protein and a 10% fat feed with a rice bran supplement such as: a href="http://www.southernstates.com/products/horsefeed/legends/legends_feeds_prb.aspx" rel="nofollow"http://www.southernstates.com/products/h…/a during the Winter.