Equine polysaccharide storage myopathy
Encyclopedia
EPSM or Equine Polysaccharide Storage Myopathy is a muscle disease most commonly associated with heavy horse breeds. Common heavy horse breeds in the United States
include the Clydesdale, Shire
, Belgian Draft or Belgian
, Suffolk Punch
and Percheron
. EPSM may also occur in the American Quarter Horse
and other light horse breeds or draft mules and horses that have draft lineage. The Quarter Horse community calls the condition PSSM (Polysaccharide Storage Myopathy). EPSM may, less commonly, be found in most other breeds including Standardbred, Arab and Thoroughbred.
tissue during exertion. It is estimated by DNA
testing that approximately two-thirds of all draft horses have the predisposition for EPSM. A biopsy test
can determine whether the horse has EPSM. An endocrine test after exercise may detect EPSM related muscle damage.
EPSM can be fatal to affected horses.
The three primary techniques for confirming a diagnosis of EPSM are
The approach considers that the horse gains no nutrition from grains, other than the calories. Since the starches and sugars in grains cause specific digestive problems, the approach is to replace starch and sugar calories with fat-based calories. The result is the 'added fats' diet. In basic outline the daily ration is divided into two feedings:
Improvement of EPSM symptoms may take 4–6 months.
Adding the fat calories (vegetable oil) to the diet is as important as removing the starches and sugars from grain sources. Depending on severity of the condition, the horse may have comfort restrictions in exercising or work, but some exercise is required to begin rebuilding damaged muscles. As the recovery proceeds, exercise may increase to best occupy the horse's attention and maintain recovery.
Molasses
is added to many feeds and grains to control dust and to sweeten (sugar) the feed to entice appetite. The sugars and starches in molasses, however, are a problem for EPSM-symptomatic horses. The horse's appetite will often decline when molasses is withdrawn. This will pass as the horse relearns the taste of feed without molasses.
Some regions are naturally selenium-sufficient, and additional supplements should be added with care. A local veterinarian can advise about local selenium levels.
Part of the hay ration may be taken as beet pulp shreds, alfalfa pellets, or a combination, to provide a carrier to pour the oil over for feeding.
The specified level of vegetable oil, 2 c./1,000 lb bodyweight, targets a dietary level of 24% calories from fat sources. Several commercial feed companies now provide feeds with reduced sugars and starches, and added fat sources. These feeds can reduce the amount of additional vegetable oil needed to meet the dietary goal ((2 c./1,000 lb)/day), or in some cases will meet the goal without additional fat calories. At least one company manufactures a dry fat supplement that can be used instead of liquid vegetable oil.
One strategy to introducing vegetable oil is to begin with 1/4 cup (125 g) vegetable oil on one feeding. Continue for several days, until the horse is eating both feedings well. Then add 1/4 c. to the other feeding for 2–3 days. Every 2–3 days increase by another 1/4 c. If at some point the horse stops accepting the increase, back up a step or two for 2–3 days and resume the progression, until the target amount for that horse is achieved. This approach is consistent with always making diet changes gradually, over at least 2–3 weeks.
Because the therapy links diet to weight of the horse, EPSM horses need to be separated at feeding time (usually 45 minutes or less), so that the horse gets fat calories proportional to body weight.
The therapy appears to be quite benign, with most horses benefiting, even non-EPSM horses. Other observed effects of the non-grain, fats based diet include improved recovery time from exercise (from trials before the Atlanta Olympics) and improved heat tolerance (reported by farmers, loggers). Horses that experience mood swings due to blood sugar excursions from starches and sugars in the diet often show a more even attitude on the added fats diet. Some horses with chronic colic have shown improvement, and some 'hard to keep' horses have been more thrifty (less feed needed to maintain condition) on the added fats diet.
The recent (1990s) announcement of the condition in horses in use for decades or centuries met with a degree of skepticism, especially as the therapy was to remove grains from the horse's diet. Anecdotal and further research has confirmed the condition.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
include the Clydesdale, Shire
Shire horse
The Shire horse is a breed of draught horse or draft horse . The breed comes in many colours, including black, bay and grey. They are a tall breed, with mares standing and over and stallions standing and over. The breed has an enormous capacity for weight pulling, and Shires have held the world...
, Belgian Draft or Belgian
Belgian (horse)
The Belgian Draft horse or Belgian, also known as Belgian Heavy Horse, Brabançon, or Brabant, is a draft horse breed from the Brabant region of modern Belgium, where it is called the or Flemish: . It is one of the strongest of the heavy breeds...
, Suffolk Punch
Suffolk Punch
The Suffolk Punch, also historically known as the Suffolk Horse or Suffolk Sorrel, is an English breed of draught horse. The breed takes the first part of its name from the county of Suffolk in East Anglia, and the name "Punch" from its solid appearance and strength...
and Percheron
Percheron
The Percheron is a breed of draft horse that originated in the Perche valley in northern France. Percherons are usually gray or black in color. They are well-muscled, and known for their intelligence and willingness to work. Although their exact origins are unknown, the ancestors of the breed were...
. EPSM may also occur in the American Quarter Horse
American Quarter Horse
The American Quarter Horse is an American breed of horse that excels at sprinting short distances. Its name came from its ability to outdistance other breeds of horses in races of a quarter mile or less; some individuals have been clocked at speeds up to 55 mph...
and other light horse breeds or draft mules and horses that have draft lineage. The Quarter Horse community calls the condition PSSM (Polysaccharide Storage Myopathy). EPSM may, less commonly, be found in most other breeds including Standardbred, Arab and Thoroughbred.
Nature of the Condition
EPSM is a genetic predisposition to fail to digest grains properly in the horse. The result leads to damage to muscleMuscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
tissue during exertion. It is estimated by DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
testing that approximately two-thirds of all draft horses have the predisposition for EPSM. A biopsy test
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
can determine whether the horse has EPSM. An endocrine test after exercise may detect EPSM related muscle damage.
EPSM can be fatal to affected horses.
Diagnosis
While many heavy horses have the predisposition for EPSM, most do not show symptoms. What triggers the condition from predisposition to active threat is not known. It may be that unexpected changes in work or diet cause the horse to lock up or over conserve electrolytes, causing failure of normal neuronal controls. The active result, failure to properly digest starches and sugars from grains, leads to a general system effect. The muscle tissues showing effect or damage varies widely. EPSM is not commonly diagnosed from symptoms, but rather by ruling out other potential causes for symptoms.The three primary techniques for confirming a diagnosis of EPSM are
- Try the added fats diet therapy for 4–6 months. If the horse improves, then EPSM is a likely suspect, and the horse is 4–6 months along the road to recovery.
- Muscle biopsy. This is a dependable, clinical diagnosis.
- Endocrine test, from a blood sample after exercise. This was the first diagnosis technique available, but is not completely reliable.
Symptoms
- Muscle wasting, especially in the rear quarters
- Muscle weakness
- Gait abnormality or lamenessLameness (equine)Lameness in horses and other equidae is a term used to refer to any number of conditions where the animal fails to travel in a regular and sound manner on all four feet...
- Work intolerance
- Poor performance
- Rhabdomyolysis ("Tying Up", "Monday Morning Sickness")
- Stringhalt
- Shivers
- A peculiar 'hitch' in a rear leg while walking
- Dis-coordination in backing
- Failure to rise after anesthesiaAnesthesiaAnesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
Therapy
Beth Valentine, DVM, proposed the first successful therapy to halt and reverse the progression of EPSM, except in advanced cases. This is a diet change. Because EPSM is a genetic condition, there can be no 'cure' in the symptomatic horse, but many affected horses can be restored to full health and work status.The approach considers that the horse gains no nutrition from grains, other than the calories. Since the starches and sugars in grains cause specific digestive problems, the approach is to replace starch and sugar calories with fat-based calories. The result is the 'added fats' diet. In basic outline the daily ration is divided into two feedings:
- 1.2% to 2.1% bodyweight in good quality forage (hay)
- 2 cups vegetable oil (corn, soy, canola) per 1,000 lb bodyweight (1 liter vegetable oil per 1,000 kg bodyweight)
- 1-2 IU (International UnitInternational unitIn pharmacology, the International Unit is a unit of measurement for the amount of a substance, based on biological activity or effect. It is abbreviated as IU, as UI , or as IE...
s) Vitamin E per pound (2 to 5 IU/kg) - Selenium supplement
- Plenty of fresh water
- Exercise to the horse's comfort level
- Usual salt and mineral supplements
Improvement of EPSM symptoms may take 4–6 months.
Adding the fat calories (vegetable oil) to the diet is as important as removing the starches and sugars from grain sources. Depending on severity of the condition, the horse may have comfort restrictions in exercising or work, but some exercise is required to begin rebuilding damaged muscles. As the recovery proceeds, exercise may increase to best occupy the horse's attention and maintain recovery.
Molasses
Molasses
Molasses is a viscous by-product of the processing of sugar cane, grapes or sugar beets into sugar. The word molasses comes from the Portuguese word melaço, which ultimately comes from mel, the Latin word for "honey". The quality of molasses depends on the maturity of the sugar cane or sugar beet,...
is added to many feeds and grains to control dust and to sweeten (sugar) the feed to entice appetite. The sugars and starches in molasses, however, are a problem for EPSM-symptomatic horses. The horse's appetite will often decline when molasses is withdrawn. This will pass as the horse relearns the taste of feed without molasses.
Some regions are naturally selenium-sufficient, and additional supplements should be added with care. A local veterinarian can advise about local selenium levels.
Part of the hay ration may be taken as beet pulp shreds, alfalfa pellets, or a combination, to provide a carrier to pour the oil over for feeding.
The specified level of vegetable oil, 2 c./1,000 lb bodyweight, targets a dietary level of 24% calories from fat sources. Several commercial feed companies now provide feeds with reduced sugars and starches, and added fat sources. These feeds can reduce the amount of additional vegetable oil needed to meet the dietary goal ((2 c./1,000 lb)/day), or in some cases will meet the goal without additional fat calories. At least one company manufactures a dry fat supplement that can be used instead of liquid vegetable oil.
One strategy to introducing vegetable oil is to begin with 1/4 cup (125 g) vegetable oil on one feeding. Continue for several days, until the horse is eating both feedings well. Then add 1/4 c. to the other feeding for 2–3 days. Every 2–3 days increase by another 1/4 c. If at some point the horse stops accepting the increase, back up a step or two for 2–3 days and resume the progression, until the target amount for that horse is achieved. This approach is consistent with always making diet changes gradually, over at least 2–3 weeks.
Because the therapy links diet to weight of the horse, EPSM horses need to be separated at feeding time (usually 45 minutes or less), so that the horse gets fat calories proportional to body weight.
The therapy appears to be quite benign, with most horses benefiting, even non-EPSM horses. Other observed effects of the non-grain, fats based diet include improved recovery time from exercise (from trials before the Atlanta Olympics) and improved heat tolerance (reported by farmers, loggers). Horses that experience mood swings due to blood sugar excursions from starches and sugars in the diet often show a more even attitude on the added fats diet. Some horses with chronic colic have shown improvement, and some 'hard to keep' horses have been more thrifty (less feed needed to maintain condition) on the added fats diet.
History
Several researchers, including Beth Valentine while working at the Cornell University pathology labs, investigated deaths of heavy horses from muscle wasting. They found a that the muscle wasting, an occasional cause of death in heavy horses, was cause by a peculiar type of starvation of the muscle. Positing the starches and sugars link, Dr. Beth proposed the vegetable oil/Vitamin E/selenium therapy, and the endocrine test to detect presence of the condition in living horses.The recent (1990s) announcement of the condition in horses in use for decades or centuries met with a degree of skepticism, especially as the therapy was to remove grains from the horse's diet. Anecdotal and further research has confirmed the condition.