Question

My Warmblood-cross mare was diagnosed with myofibrillar myopathy through muscle biopsy. While my vet has been amazingly supportive and persistent in achieving this diagnosis, she admits that she is not well versed in nutrition. She mentioned that changing my mare’s diet, including the addition of an amino acid supplement, might help her become more comfortable and perhaps rideable. Can you help me understand what she’s referring to?

Answer

Myofibrillar myopathy (MFM) is a disorder characterized by exercise intolerance and occasional tying-up. Because you and your veterinarian worked diligently to achieve a diagnosis, you’re one step ahead of many horse owners dealing with the frustration that often accompanies muscle disorders.

As to her diet, I will provide broad-stroke recommendations that might be fine-tuned as you consider your mare’s individual needs. For horses diagnosed with MFM, well-balanced diets should focus on providing quality protein, including specific amino acids, and antioxidants to counteract muscle deterioration and atrophy.

As with most other horses, those diagnosed with MFM should consume 1.5-2% of their body weight in forage (pasture, hay) per day. Hay should be selected to match the horse’s caloric needs. An easy keeper might do well on grass hay, while a hard keeper may do better on legume-grass mixed hay.

Choose a concentrate from a trusted manufacturer and study the nutritional information on the bag. Concentrates for MFM horses should include higher levels of protein (12-14% crude protein), moderate levels of nonstructural carbohydrates (NSC) (20-30%), and fat (4-8%). Of particular note, there is no evidence to suggest that low-NSC, high-fat diets are needed by Warmbloods diagnosed with MFM.

Supplemental amino acids are essential for horses diagnosed with MFM. Look for a supplement rich in cysteine, such as MFM Pellet, developed by Kentucky Equine Research in collaboration with Dr. Stephanie Valberg, an authority on muscle diseases in horses. Many horses have found relief from the disease through these diet changes and supplementation with MFM Pellet and high-quality antioxidants such as Nano-E or Nano-Q10.

Read about one of the many horses that have benefited from MFM Pellet.

Additional reading: Feeding Performance Horses with Myopathies, published in the American Association of Equine Practitioners Proceedings, 2020.