Dr. Beth,
Long story, somewhat short: I have a now 6 yo warmblood gelding clinically diagnosed with epsm in August 2009 at age 5. The horse had exhibited some problems with muscle development and behavioral issues during training off and on since age 3, and then in summer 2009 as work advanced just "fell apart" with muscle loss on the topline, hind end stiffness/lameness and lack of energy. I started him on the epsm diet/program (ultium, corn oil, vit e, full turn out and work 4-5days per week) in late August 2009 and he has been in consistent work since. It took about 6 months to get a decent canter back. Now almost one year later, does not look or act like the same horse. Recovery nothing short of miraculous: He grew about 1", filled out topline, movement improved, muscled up, enthusiasm improved, stiffness seemed to resolve.... until about 6 weeks ago. Now seems to have recurrence of gait stiffness, reluctance to canter, holding tail slightly to side - all much milder-- but identical to symptoms he had at the time of presumptive diagnosis. Changes over the last 2 months of relevance: high temps, increased grass in pasture and (perhaps) inadequate dietary intake fat due to the fact that I did not recalculate needs with weight gain and growth.... In addition, while always a slightly picky eater, with increased pasture forage, he is turning up his nose at oily feed at bottom of bucket- not finishing at times.. and my attempts to switch him gradually to higher fat supplements (Nutrena empower) for a lower volume of feed and oil --have not been successful, even with slow introduction and molasses added. I know I need to get a weight tape and recalculate his dietary needs because he is now a hefty 16.2H and original calculations were for a weight of around 1000lbs...But I have more questions about his current situation:
1. Horse is a nice weight, not obese --but are grazing muzzles indicated simply to manage starch/forage intake in the epsm horse? Can good pasture upset the applecart even in an epsm horse with appropriate fat content in diet? Will increased fat admin (above and beyond 1lb/1000lb/day) "override" high grass intake? If so, how much should fat be increased OR is starch reduction necessary with grazing muzzle regardless of horse weight?
2. I have been feeding ultium and corn oil - he is not crazy about either..turns nose up at nutrena empower. What do you find are the most palatable and epsm diet acceptable feeds --that will also absorb oil? What is your experience with palatability of supplements like cool calories in picky eaters? You mentioned in one of your articles about starch contents less than 33%.. but all I see on the specs for feeds is fiber content - which would not include total starch - do I need to calculate starch content if my horse is sensitive to this? If so, where does one obtain this information for feeds...
3. Finally, how efficient are veterinarians discerning the cause of hind end stiffness in the epsm horse? Since his symptoms are identical to previous but milder - I am reluctant to have a veterinarian do a big lameness work up for a problem that is likely already apparent. I am wondering if flexions are likely to be positive in the epsm horse anyway and lead the vet down the path to a big work up for things like hock disease etc. that aren't there...
Thanks for your help. Your site has been a wonderful resource for me in the last year.

Hi Louise. I am so glad to hear that your horse responded so well. The problems now mean something is out of balance in his diet and exercise, and I absolutely agree that less fat intake and more grass intake are likely problems. Definitely recalculate fat intake and yes Cool Calories can substitute for fat. Just remember that Cool Calories weigh half their volume, so it takes 2 cups Cool Calories to provide the same amount of fat in 1 cup of oil. A grazing muzzle sounds like a good idea because it will reduce his grass intake and also, hopefully, give him more of an appetite. Rice bran powder with 20% fat can also help to soak up oil and also add some fat. Soaking any feed in water helps to absorb oil better. Unfortunately you can't find starch content on the bag because companies are not legally allowed to do that. Most equine feed companies now know the starch content if you ask them, though. As to veterinarian efficiency, it is just now that the idea that hind gait abnormalities are as much as sign of EPSM as is tying up. In fact, gait problems are more common than tying up. If some adjustments to his diet don't show any effect on his gait in a few weeks I'd definitely get the exam, though. EPSM should not give a positive flexion test unless it causes a cramp, which generally looks very different than a joint related lameness.

I apologize for rambling a bit, and I hope this makes sense and helps!

Thanks for your prompt response. I did take some tape measurements today and his weight is calculating out to 1200-1300 lbs so I do think his fat intake has probably been marginal. I did try adding the water to part of the ultium to absorb the oil - but he tends to leave the crumbles tho... would switching to a senior feed - which he has liked in the past - be ok from the starch perspective, if I can make up the difference in oil? Thanks for your help. will look into the muzzles also. All makes great sense!

Senior feeds are also pretty low in starch and sugar and typically work in an EPSM diet.