Question

My young Hanoverian mare is showing signs of PSSM, or possibly MFM, including metabolic markers indicative of disease. Her gaits have become more restricted, and she can be explosive under saddle, bucking a lot at the canter and swapping leads willy-nilly. At the end of our rides, even short, uncomplicated schooling sessions, she is tense, hypersensitive, and dripping in sweat. She is extremely sensitive to touch. We have modified her diet as if she has PSSM, including adding Re-Leve. Should I provide other supplements? 

Answer

Because there is not yet a genetic test defined for PSSM2/MFM, a muscle biopsy may help determine the specific myopathy affecting your mare. Significant differences in dietary recommendations between the two diseases have been developed, so getting a more definitive diagnosis would be best.

Traditionally, the dietary approach for performance horses diagnosed with exertional rhabdomyolysis has been a low-starch, high-fat, high-fiber concentrate. Horses diagnosed with MFM, however, are not as sensitive to starch and may actually react negatively to high fat concentrations in their diets. Dietary recommendations for MFM include concentrates with moderate starch and fat, and supplementation with specific amino acids.

For all muscle myopathies, we recommend antioxidant supplementation to help address damage to the muscle tissue, including Nano-E (a natural-source vitamin E shown to have the highest bioavailability in horses) and Nano-Q10 (a rapidly absorbed source of coenzyme Q10). For PSSM2 and MFM in Warmbloods, we also recommend MFM Pellet, as its specific amino acid profile has been shown to be helpful for horses with these myopathies. MFM Pellet contains branched chain amino acids and N-acetyl cysteine, as well as other amino acids.

Kentucky Equine Research has collaborated for many years with Stephanie Valberg, D.VM., Ph.D., Dipl. ACVIM, ACVSMR, Director of the Equine Neuromuscular Diagnostic Laboratory and Mary Anne McPhail Dressage Chair in Equine Sports Medicine at Michigan State University. Learn more on the lab’s website, including specific information about how to submit a muscle biopsy.

Would you like to know more about the history of myopathy in horses? Check out Then and Now: A Brief on Equine Muscle Disease, originally published in the proceedings of the 2018 Kentucky Equine Research Conference. This Q&A with Dr. Valberg starts on page 73.