Question

I recently imported a six-year-old Warmblood gelding. He arrived slightly undermuscled but otherwise in good condition. His diet consists of 5 lb (2.3 kg) of a high-fat performance feed and 2 lb (0.9 kg) of a fiber-based feed in addition to grass hay. Over the last few months, he has become very resistant to moving forward under saddle, acting dull and distracted much of the time. In his stall, he chews wood and rarely finishes his meals. These behaviors made me think he could be dealing with hindgut acidosis. We’ve ruled out lameness and saddle fit problems. I have taken all of the steps to improve his musculature with gradual strength training when he is cooperative. One veterinarian advised focusing on reducing muscle soreness and building muscle by adding whey protein to his diet. I added MFM Pellet and whey isolate. What other steps should I take to improve his performance and overall well-being?

Answer

Thank you for providing detailed information about your gelding’s diet and history. Pinpointing the reason for a decline in performance can sometimes be challenging. Many times a combination of factors may be at play. Because of this, working with a veterinarian and a nutrition team is a sound approach. From the description you’ve given, it seems you are on the right track with his diet, though you might consider a few small changes.

While wood-chewing and inappetence can be signs of hindgut acidosis, they could also point to a different gastrointestinal disorder. These signs, along with his pain-related behavior and lack of impulsion under saddle, are signs typical of equine gastric ulcer syndrome (EGUS), specifically equine glandular gastric disease (EGGD). One study revealed Warmbloods were at a greater risk of EGGD compared to other breeds, often with none of the traditional ulcer risk factors. Discuss these observations with your vet to determine if further diagnostics are warranted, as the only way to gather a definitive diagnosis of gastric ulcers is through gastroscopy. In the meantime, there are a few steps you can take to reduce the risk of gastric ulcers and hindgut acidosis.

• Although your gelding does not consume a large amount of concentrate, it would be ideal to split the total amount of concentrate into three meals a day. Smaller meals help ensure that nonstructural carbohydrates, like starch, are digested prior to reaching the hindgut. If they reach the hindgut, they will ferment and lower the pH of the cecum and colon, setting up the hindgut for acidosis.
• Adding appropriate digestive health supplements to each meal can support gastric and hindgut health.
• Other management practices recommended to reduce the risk of digestive problems include offering free-choice hay throughout the day –and feeding alfalfa hay and a buffer prior to exercise. Some researchers suggest building two or three complete rest days into a horse’s schedule, when possible, to help reduce stress related to increased EGGD.

A final word about your gelding’s fluctuating appetite: his inappetence could be a response to the concentrated content of amino acid supplements, which can be off-putting to picky eaters. Although it is an unlikely scenario for your gelding, some horses start chewing wood out of boredom or lack of forage.

Want to learn more about ulcers? Jump to Overview of Gastric and Colonic Ulcers, a review paper written by Frank Andrews, D.V.M., a world-renowned expert in gastric ulcer disease, for Advances in Equine Nutrition IV, published by Kentucky Equine Research.

If your gelding’s performance continues to suffer and the willingness to go forward does not improve, then you may consider making a significant diet change often recommended for horses with myofibrillar myopathy (MFM). Although you didn’t mention it specifically, I suspect you believe your horse may have myofibrillar myopathy. Assuming the grass hay is good quality, most of his current diet is in line with MFM recommendations with the exception of the high-fat feed and antioxidant supplementation.

Feeds with moderate fat (4-8%) are recommended because fat is a potential source of oxidative stress, which should be reduced as much as possible. MFM horses tend to do best on products with 20-30% nonstructural carbohydrates, which will help improve energy under saddle. The only downside to this amount of nonstructural carbohydrate is that it doesn’t coincide with the low-starch diet recommendations for horses with squamous gastric ulcers and hindgut acidosis. The best way to maintain digestive health while feeding a concentrate with a moderate level of nonstructural carbohydrates is to offer it in several small meals and include RiteTrac for buffering support.

High-quality amino acid supplementation from whey protein sources is recommended for horses diagnosed with MFM. The concentrated source of amino acids and N-acetyl cysteine found in MFM Pellet is supplying effective levels without the need for additional whey supplementation. However, if you are feeding the whey isolate after exercise and the MFM Pellet in the other two meals, then this program could be continued.

Supplementation with the antioxidants Nano-E (natural-source nanodispersed vitamin E) and Nano-Q10 (coenzyme Q10) is recommended for horses suspected of having MFM and struggling with muscle development.

In addition to free-choice salt, consider adding a daily electrolyte supplement if he is going to be working intensely enough to sweat.

If you continue to experience problems after modifying the diet with the suggestions above and addressing digestive concerns, you may consider having your vet contact the Equine Neuromuscular Diagnostic Laboratory at Michigan State University about the possibility of submitting a muscle biopsy to confirm or rule out potential myopathies.

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