Question: I have a 14yo Gelding in upstate New York.  This is his current feed regimen broken into AM and PM feeds:
25.2oz beet pulp
15oz crimped oats
25.28oz chopped alfalfa
4.4oz ground flax seed
3.6oz salt - 2 years
15iu add’l vitamin E
1mg add’l selenium
1.3oz “Just add oats” multivitamin

In addition he gets free choice hay 24/7 as well as free choice mineral salts.  From what I can tell the hay is a mix of timothy, alfalfa and orchard grass.  He is mainly a trail riding and some long distance riding.

For about 9 months I have been taking lessons with a dressage trainer who is helping me correct how he carries himself - head high, short strided gaits. He is not really a high strung Arab. For about a year or better I have a rehab massage therapist work on him regularly as I have struggles with saddle fit and back tenderness.  He is improving but I think I may need to change his nutrition to move him along faster. I am looking for any suggestions you may have regarding his nutrition.

Dr. Kellon:  The Just Add Oats is not appropriate for what you are feeding him and is making a diet likely already high in calcium even higher. If you can tell  me where his hay was grown I can suggest a better match. Roughly how much alfalfa is in it? 
Since he is an Arabian, it would be wise to check his insulin level. High insulins can result in nagging hoof pain that could explain his way of moving.  Otherwise, active horses often benefit from the inclusion of a joint supplement in their routine. Uckele Lubrigen is a good place to start.