I like SmartHoof, which I am using as kind of a generic CA Trace. CA Trace was originally formulated for horses on the west coast, as the idea is that west coast hay is generally high in iron, which causes a deficiency in copper and zinc (their website used to explain this, I'm not sure if it still does).

Another one I really like is Bioflax 20 or Bioflax Ultra by Horsetech.

http://www.horsetech.com/