If you have a horse that has been diagnosed with a genetic muscle disorder such as Polysaccharide Storage Myopathy (PSSM) or Recurrent Rhabdomyolysis (RER), you’ve likely heard about the benefits of switching to a high fat/low NSC horse feed. But how is a high fat diet beneficial for a horse exactly?
To begin with, it’s important to note that while PSSM and RER are two different conditions, both cause irregularities in the cells which can lead to tying up. Therefore, both are treated similarly when it comes to nutrition.
Research has shown that reducing or eliminating dietary carbohydrates and replacing them with fat limits the amount of sugar that can be converted into glycogen in the muscles; this is critical for PSSM horses but is also beneficial for RER horses.
Fat as energy
Fats and oils belong to a class of molecules called lipids which come as either a single molecule or a chain of molecules, known as a fatty acid. Fatty acids vary in length but can be further subdivided into 2 categories: saturated and unsaturated.
Saturated fats mainly come from animal sources, while unsaturated fats usually come from plant sources.
The most common fat sources in a horse’s diet are vegetable oils, rice bran, and flaxseed.
For horses, the majority of fat digestion occurs in the small intestine, but some fat moves on to the liver, adipose tissue, or to other parts of the body where it can be either stored or utilized as energy.
In fact, fat contains over twice the amount of energy as either carbohydrates or protein, and studies have shown that when fat is substituted for carbohydrates in the diet, blood glucose and insulin responses are also reduced.
Low carb (low NSC) horse feed
Non-structural carbohydrates (NSCs) are found in corn, wheat, oats, barley and molasses, which are all common feed ingredients, but as stated previously, avoiding diets high in carbohydrates is crucial for both RER and PSSM horses.
That is why many feed companies now offer high-fat diets specifically designed for these sensitive horses.
However, keep in mind that forage--both grasses and some types of hay-- is another common source of NSCs. Therefore, it’s important to limit green pasture for PSSM horses, especially, and get your hay tested as well. Having an NSC level of 12% or lower in your forage (think: low carb horse hay) is best for these animals. Studies have shown that RER horses can tolerate higher NSC levels in forage, but caution is still advised.
The importance of equine exercise training
Though feeding a high fat diet can make a big difference for horses with equine muscle disorders, we can’t forget the importance of exercise, which suppresses sugar uptake and also helps horses to better metabolize sugars.
Additionally, PSSM horses use excess glycogen as fuel, so this leads to less accumulation in the muscles. As a result, daily exercise (without days off) is recommended for any horse diagnosed with a muscle disease. In fact, studies show that while 50% of PSSM horses improve with diet changes alone, 90% improve with both diet changes AND exercise.
High fat diets for horses without muscle disorders
In addition to being beneficial for horses with RER or PSSM, high fat diets appear to be helpful for some other horses, such as those in hard training or work. Fat contains more than twice the amount of energy than carbohydrates, making high fat feeds or supplements a safe and efficient energy source for performance horses. Studies also show that horses on high fat (or low NSC) diets tend to perform longer without fatigue, and this may have something to do with the fact that the digestion of fat produces less internal body heat when compared to high carbohydrate or high protein diets.
Increasing dietary fat is also a good way to increase calories without drastically increasing the amount of concentrates fed which can be beneficial for broodmares or any horse needing to gain weight.
Likewise, swapping out fat for carbohydrates appears to help horses with insulin resistance or equine metabolic syndrome by improving insulin sensitivity. Additionally, a high fat diet may also help horses with gastric ulcers, though more research is needed in this specific area.
As with any diet change, the transition from a higher carbohydrate to high fat diet should be done gradually over a period of several days.
Take home message
When managing a horse affected by a muscle disorder, diet and exercise are paramount to their continued success, and switching to a high fat (low carb) horse feed can make a significant difference in their health. High fat diets also have their place for some horses without muscle conditions, as discussed above.
As another piece of the diet puzzle, specific supplements, made with high-potency antioxidants, can also help to improve your horse’s quality of life. Follow these recommendations, along with cultivating a close relationship with your veterinarian, and your horse will assuredly benefit from it!