Balanced Equine - EPSM/PSSM/tying up. Equine Polysaccharide Storage Myopathy (EPSM) is a genetically programmed cause of tying up (Exertional rhabdomyolysis). Tying up is characterised by painful muscle cramping when the horse is exercising, it can range from a reluctance to move to an acute episode with the horse completely seized up. The muscle pigment myoglobin causes red brown discolouration of the urine from muscle breakdown. EC Stock Photo of Quarter Horse published in 'The Equine Chronicle Online'http: //www. Tying up is a symptom rather than a specific disorder. There are two categories with tying up, horses that have sporadic/isolated episodes and those that have repeated episodes. Isolated episodes are more likely to be due to management/dietary factors. Common causes include electrolyte imbalances to plain overworking of a horse to heat stroke. EPSM on the other hand is a genetic cause. EPSM was first described by Dr. Beth Valentine (Oregon State University) to describe the condition in Draft horses and Polysaccharide Storage Myopathy (PSSM) was coined by Dr. Stephanie Valberg (University of Minnesota) when she first described the condition in Quarter Horses. Since then EPSM or PSSM have been found to occur in other breeds. One study documented PSSM in Warmbloods, Anglo Arabs and Andalusians. Horses with EPSM or PSSM have abnormal glycogen in their muscles. Glycogen is the storage form of glucose. In one form, the glycogen is resistant to breakdown. This is the . In another form of the disease, the glycogen is normal but found in abnormal locations.
Mc. Cue and Valberg of Minnesota recently found a genetic mutation in horses with the classical form. This causes them to produce glycogen at a faster than normal rate. Since the enzyme systems in muscle cells prevent them from burning and forming glycogen at the same time, they likely have less glucose available for energy. It is still unknown what the root of the problem is in the other form of EPSM/PSSM, but we know that Quarter Horses with PSSM and all Draft horses have high uptake of glucose into their muscle cells, or . Bottom line is that there are many possible causes, end result is an energy shortage in the muscle cell that prevents it from relaxing. Over time it is understandable that the terms EPSM and PSSM have become interchangeable but there are notable differences depending on breed, the studies just mentioned show Quarter Horses with PSSM are very insulin sensitive compared to other Quarter Horses whereas in Draft horses, both effected EPSM horses and non EPSM have the same high insulin sensitivity. The proportions of the types of muscle fibres matters. Draft horses have a higher percentage of type 2. A muscle fibres and Quarter Horses have a higher concentration of type 2. B muscle fibres. Both of these fibre types are red, . This gives the draft horse the ability to haul heavy loads and the Quarter Horse blazing speed over short distances. Fat can only be burned aerobically, meaning in presence of oxygen by mitochondria, the . No matter how much fat is available, the 2. B . When glycogen runs low, the 2. B muscle fibres are in big trouble, for this reason PSSM Quarter Horses are always associated with muscle damage, tying up and elevated muscle enzymes. There is a higher density of mitochondria in 2. A muscle fibres, the greater the number of mitochondria, the greater ability to burn fat. Draft horses are more likely to show symptoms of weakness and muscle loss and may do so without marked elevations of muscle enzymes or myoglobin, meaning it’s not necessarily a tying up issue. Diagnosis and symptoms. The symptoms of acute tying up can be very dramatic but acute back pain from poor saddle fit, colic and pedal bone fractures can present with similar symptoms. Horses can have darkish coloured urine which looks likes it’s stained by myoglobin but are simply dehydrated. Symptoms such as tripping can be caused poorly balanced hooves with toes too long. There is a concern that it’s being over diagnosed. Horses may display a number of the following signs: unhappy attitudetrippingresistance to holding up the hind feetsubtle lameness episodestires easilybuckingkicking at nonexistent flies (muscle cramps)muscle twitching or sensitivitystiff or hard musclesweakness or muscle losstying upreluctance to . Previously, the only diagnostic tool was a muscle biopsy to see if there is increased glycogen storage and to look at the structure of glycogen. Horses with PSSM have lower than normal numbers of mitochondria. Since mid 2. 00. 8, a genetic test has been developed by Geneticist Dr. Molly Mc. Cue at the University of Minnesota, in conjunction with Dr. James Mickelson and Dr. Stephanie Valberg. In Drafts, 8. 7% of PPSM/EPSM cases have a genetic mutation for an enzyme involved in the manufacturing of glycogen. The same mutation is found in 7. Quarter Horses. Quarter Horses and related Quarter Horse breeds may have a second mutation called the modifying gene, a positive for both mutations will have more severe signs of the disease. Treatment. All breeds of horse with PSSM benefit from regular exercise to improve their capacity to burn fuels with oxygen and a high fibre, grain- restricted or grain- free diet which will limit the amount of glycogen in the muscle cells. Regular exercise can increase the number of mitochondria and can even cause some muscle fibre types to switch over to aerobic capacity. The greater the number of mitochondria, the more fat can be used as a fuel. Many horses diagnosed with EPSM/PSSM have been helped by changing their diet to include at least 1. Supplemental fat is likely to be of more benefit to Draft than Quarter Horses because of their higher percentage of muscle fibre types that can efficiently burn fat. The high fat feeding proponents say the fat gives the muscle an alternate energy source, and high fat feeding . This may be so but it may be slowing down carbohydrate metabolism. Horses evolved on high fermentable fibre derived from plant vegetation with less than 6% of the diet as fat. Digestion of fibre starts in the upper portion of the stomach where bacteria begin the job of fermenting sugars and starches into products that can be burned directly in the mitochondria to produce energy. The efficiency of fat digestion in horses is amazingly high, about 8. Since the level of fat is so low in vegetation perhaps that’s why horses need to be so efficient with absorbing fat for the essential omega- 3 and omega- 6 fatty acids in plants. Feeding high levels of fat can come at a cost. One 2. 00. 2 study found a 1. IR), especially for horses known to be . Horses can develop insulin resistance and be more susceptible to laminitis (founder). Insulin resistance affects blood sugar regulation and is similar to type 2 diabetes mellitus in people. One of the triggers can be a high fat diet; fat has been used by researchers to induce a state of insulin resistance in horses. One 2. 00. 5 study by Dr Nicholas Frank and others used the equivalent of just under a cup of rice bran oil and induced insulin resistance in Thoroughbreds. Dr Eleanor Kellon VMD, an equine nutrition specialist recommends a different approach “I've lost track of how many horses suspected to have PSSM/EPSM and put on high fat diets end up with me because they get insulin resistance and laminitic. We don't know the safe dose of fat for an insulin resistant horse, but we sure don't want to be feeding as much fat as is already known to induce insulin resistance in a normal horse!”Her approach is to limit carbohydrates and supplement with L- carnitine to assist in getting fat from body stores into the mitochondria, in conjunction with regular exercise and a mineral balanced diet. Gro 'n Win ® Versatile feed to complement a forage-first diet; Lower feeding rate and 13% NSC (sugar and starch) 5x the vitamins and minerals of most feeds; no.L- carnitine is a type of amino acid, necessary for moving long chain fatty acids into the mitochondria to be burned. Studies have shown that availability of free carnitine in the muscle cell influences the relative rate of burning of fat or carbohydrate. Even normal horses in training benefit from L- carnitine supplementation, showing higher metabolic efficiency during exercise. With L- carnitine supplementation, it's been possible to greatly reduce or eliminate high fat feeding, with better results. Inside the body, L- carnitine exists either in the free, L- carnitine, form or as acetyl- L- carnitine. More recently, Dr. Kellon has been using the acetyl- L- carnitine form because a laboratory study has found acetyl- L- carnitine can turn on a pivotal enzyme which directs glucose into the mitochondria to be burned rather than into pathways that produce glycogen. Dr. Kellon says, “Until we know more details of the biochemistry of EPSM/PSSM, it's important to treat each case as an individual. How a horse responds to treatment depends both on the disorder and other underlying features of their metabolism. Some horses respond quite well to the high fat diet, others relapse or have a partial response. Some have complications. The L- carnitine and acetyl- l- carnitine has helped many horses improve further.”Originally published in the April - May 2. Vol 3. 2 No 6) issue of Hoofbeats magazine. Further reading: Dr Eleanor Kellon offers equine nutrition courses, NRCPlushttp: //drkellon. NRC Nutrient Requirements of Horses (2. N Frank, FM Andrews, SB Elliott, J Lew and RC Boston (2. Effects of rice bran oil on plasma lipid concentrations, lipoprotein composition, and glucose dynamics in mares, Journal of Animal Science 2. T6. Dr Beth Valentine DVM Ph. PSSM - Polysaccharide Storage Myopathy. Av: Anna Eriksson. PSSM är en muskelsjukdom som orsakas av en defekt (muterad) gen, vars namn är GYS1 när det gäller PSSM. EPM Prevention Summary. There have been several clinical studies aimed at unlocking the mystery of why 98% of exposed horses can clear an EPM protozoa infection. The journey with my horse and equine polysaccharide storage myopathy, PSSM, also known as EPSM in draft horses. DEPSM—Muscle Disease in Draft Horseshttp: //www.
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