Question
Flint is my 18-hand crossbred draft gelding. We think he’s in his early to mid-20s based on his teeth and the history I’ve stitched together. He’s in moderate body condition, somewhere near 1,650 lb (750 kg). He’s turned out 24/7, but the pasture is sparse. He has access to clean grassy hay as well as some alfalfa all day long. He’s also fed 3 lb (1.4 kg) of balancer pellet, 3 cups (750 ml) of vegetable oil, and 2 cups (500 ml) of cocosoya oil daily. Two specific questions about his diet: (1) can I feed lespedeza given his PSSM1 diagnosis, and (2) can I switch to a generic vegetable oil? While Flint is sound and healthy now, I am concerned about keeping him on a diet that respects his muscle problems and his caloric requirements.
Answer
Flint’s current forage and ration balancer appear to be meeting his basic nutrient requirements, but a few supplement changes may better support his muscle health, especially given his diagnosis of polysaccharide storage myopathy type 1 (PSSM1).
Assuming the current hay contains 12% or less nonstructural carbohydrates (NSC), it is appropriate for Flint. Having hay tested by a reputable lab is the only way to accurately measure NSC content. Several variables can affect NSC content (weather patterns during growth and harvest, for example, among others), so simply eyeballing the hay reveals little useful nutritional information regarding NSC.
While grass hay varies in NSC content—from 7-17%—legumes typically contain about 10%. Depending on its quality, lespedeza could replace the alfalfa in the diet as it is also a nutrient-rich legume, assuming the hay is high quality. If you are able to inspect the lespedeza prior to purchase, ensure it contains plenty of leaves since leaf shatter can be significant, rendering the hay less nutritious.
The current recommendation for fat supplementation of PSSM1 horses is 20% of total digestible energy. The National Research Council advises keeping soy oil supplementation to 0.7 g/kg of body weight per day to reduce the chance of negatively influencing fiber digestion. With this in mind, reducing the oil to 2.5 cups (625 ml) daily would be a more appropriate intake for his size. You could make up for the decrease in digestible energy from reduced oil by adding fiber sources or by switching to a high-fat, high-fiber feed.
Maintaining a balanced omega-3 to omega-6 ratio can be challenging when adding large amounts of oil. Both vegetable oil and cocosoya oil contain significantly more omega-6 fatty acids than omega-3s. Canola oil has a slightly more beneficial omega profile than vegetable oil, so this too might be an option.
Adding a concentrated source of DHA and EPA—which are long-chain polyunsaturated omega-3 fatty acids—through supplementation with EO-3 will help balance the skewed omega ratio in Flint’s diet. DHA and EPA are prevalent in certain marine-derived oils, and research shows marine-derived sources are more effective at providing DHA and EPA than plant-derived sources. DHA and EPA contain potent anti-inflammatory benefits and are recommended for a variety of inflammatory conditions.
Because Flint is fed a high-fat diet, he would benefit from antioxidant support with a bioavailable source of vitamin E. While burning fat may be energy-efficient, it causes oxidation, so a high-quality antioxidant supplement can stop some of the damage caused by oxidation. The general recommendation is 1-1.5 IU of vitamin E for every milliliter (ml) of added oil.
Natural‐source vitamin E (d‐alpha‐tocopherol) is the best form of vitamin E to offer, especially when compared to synthetic forms (dl‐alpha‐tocopherol). Nano-E is a water‐soluble, natural‐source form of vitamin E that is rapidly available to the horse, providing protection to the muscle. Top-dressing his meals with 2,500 IU of Nano-E daily would meet his increased requirements, help reduce muscle soreness, and support immune function.
Take a deeper dive into myopathies and their management by reviewing this technical bulletin: Nutritional Considerations for Horses with Myopathies.
