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metabolism and glycogen synthesis. Fatty acids are used more by type-1 oxidative muscle fibers (slow-twitch) to produce energy. The type-2 glycolytic muscle fibers (fast-twitch) are more affected by PSSM because of the mutation in the glycogen synthase gene. Horses with PSSM need low-sugar diets along with high fat. Fat provides more calories to a horse that needs energy supplementation without having to feed grain sources of carbohydrates.
Benefits for managing PSSM are achieved with 1 – 2 pounds of fat in the daily diet. It can be tricky to get some horses to eat two pounds of fat (as oil) per day. A fat supplement that is more palatable is rice bran, which can be fed
in amounts as much as five pounds per day. To improve PSSM clinical signs of muscle stiffness additionally requires incremental increases
in daily exercise. Clinical improvement for PSSM is more dependent on the amount of daily exercise and turnout than on the length or amount of dietary fat supplementation. Consistent fat supplementation without implementing a structured daily exercise regime in PSSM horses is likely to result in failure; confinement while consuming high levels of fat is likely to lead to obesity.
FAT FOR GASTRIC ULCERS
Research shows a lower incidence and severity of gastric ulcers in horses fed grain plus alfalfa as compared with those fed only brome hay. A study at Texas A&M reported that horses turned out on pasture developed more ulcers than the same horses eating alfalfa hay. Although attempts have been made to moderate development of gastric ulcers by feeding fat, there is no evidence that this is as beneficial as hoped.
In another study, results did not support the hypothesis that fat supplementation inhibits the development of gastric ulcers in horses. However, in this study, oils were added to a high-grain diet that was fed to induce ulcers, and the supplement was only given once a day. Fat supplementation to prevent gastric ulcers on other diets may require more frequent administration.
FAT FOR ANTI-INFLAMMATORY PROPERTIES
Some fats provide a great source of omega-3 fatty acids, while others, like corn oil, are higher in omega-6 fatty acids. There has been considerable discussion about the merits of omega-3 fatty acids in thwarting inflammation, including inflammation associated with some forms of equine asthma. Three major types
of omega-3 fatty acids exist in foods: alpha- linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
Feeding alfalfa in addition to grain can decrease the occurrence and severity of gastric ulcers in horses.
Not all omega-3 fatty acids are the
same. Plant-based (flaxseed) is ALA, and the marine-based (some algae and cold-water fish oil) are DHA and EPA. The body has limited ability to convert ALA to DHA and EPA. Most studies have been done with humans with some extrapolations to horses. People who bruise easily or are taking blood-thinning medications are cautioned about the use of excessive omega-3 intake since this may lead to bleeding. With this in mind, use of omega-3 fatty acid supplements may not be appropriate for horses with exercise-induced pulmonary hemorrhage (EIPH). One study supplemented EIPH- affected racehorses with DHA and reported
no reduction in inflammatory response and no improvement in severity of EIPH.
Studies comparing measures of immune cell function outside the body have demonstrated immunosuppressive effects at fairly low doses of EPA and DHA. There isn’t any work
to demonstrate this in the living horse but
SPEEDHORSE
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VETERINARY VIEWS
An increase in daily exercise can help improve muscle stiffness in horses with polysaccharide storage myopathy (PSSM).
Rice bran is a more palatable fat supplement that can be fed in amounts as much as five pounds per day.
Confinement and lack of exercise while feeding high levels of fat can lead to obesity.