My draft gets a 20% fat top dressing, Omegatin, plus flax seed, oil, supplements and hay cubes to soak up the oil. He gets enough fat to make up about 20% of his diet (counting his hay).
Dietary Recommendations for a Horse with EPSM
by Beth A. Valentine, DVM, PhD
"Overhauling your horse's diet is the first line of treatment against EPSM. The goal of the EPSM diet is to decrease soluble dietary carbohydrates (grain) and increase fat. You want to provide 20% to 25% of total daily calories from fat."
You'd think he would be fat from all the oils, but he isn't.