Dr Beth,
My 18 year old Belgian mare, Magic, has been with me since 2003. We discovered her EPSM within a couple of months and made diet changes with great results. She has been stable with her diet for the past almost 5 years, but has taken a major backslide in the past month or two.

We live in AZ....she has 24/7 turnout on 2+ acres with 5 other horses. Right now all of the pasture is dormant so more Bermuda grass hay is provided daily for all as free choice.

Magic's diet has been with Bermuda Blend pellets, rice bran, 2000IU Vitamin E, Hoof supplement, Substitute Bute, No Grain,Grain mix(from Advanced Biological Concepts,designed for EPSM) along with ABC's Plus(daily enzyme, mineral supplement) and Jeremy's Joint Jolt from ABC.

Her daily regimen is of a pasture horse with occasional hand walks and some light riding once a week, until recently. But as she was when we first got her from the PMU farm, she spends a lot of hours down, snoozing. Her gait is very slow and choppy and you can see that she is not feeling well. She is continuing to get worse and as we have upped her rice bran(which always helped in the past)...we have also added a flake or two of Alfalfa hay at night with our freezing temperatures and her inability to keep her weight up.
She is not a fan of added oil (nor am I) so the No Grain grain mix and rice bran is her main source of fat.
I have read the articles again on the website and the only thing that she is missing is daily forced exercise. As her unwillingness to move around in the pasture is gaining its role for her...I am thinking that we go back to our daily hand walks in hopes that her body will kick in to using her diet more effectively.
I am open to any suggestions and would appreciate any help that you can provide.
Thanks!

The main thing I see here is that you are unlikely to be feeding 1 lb fat per 1000 lbs of horse per day with her current diet. So, I would really recommend adding some oil to her diet. Any type of digestible oil is fine, and so if you prefer try safflower, flax, unrefined soy oil, or something else that you feel better about feeding. Even 1/2 to 1 cup per day may be enough to make a difference. Or try adding some dry fat supplement. Daily hand walks can help also. But, again, please work to get even more fat in her diet - this sounds very serious to me. And, of course, be sure to have your veterinarian check for other problems. Good luck, and definitely let us know how things go.