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Tyup horse medsTy-up horses develop stiffness and pain in the lower back, gluteal muscles and the muscles of the thigh region.  The problems can vary from a transient cramping to a very serious problem where muscle destruction occurs.  In cases of muscle destruction the urine will turn dark with myoglobin, a component of muscle cells.  The darker the urine, the more muscle damage.

There have been many proposed mechanisms for tying up, but frequently electrolyte concentrations are a major factor in ty-up horses during intense exercise.  In the 1990’s, it became evident that many cases were due to a defect in carbohydrate metabolism within affected skeletal muscle fibers.  This condition has been dubbed – Equine Polysaccharide Storage Myopathy (EPSM), and has led to some new treatment options that have shown great success. It has been suggested that this may be an inherited disease with an autosomal recessive pattern.

Typical signs of tying up are:

1. A stiff walk or jog, that at its worse, can totally immobilize the horse.

2. Hard and painful muscles in the rear.

3. If the pain is severe enough, sweating may occur.

Ty-up horses usually have recurring problems, associated with a specific set of circumstances.  For horses that work for a living, a common problem is “Monday morning disease”.  This problem occurs when horses, which were working all week, did not have their grain cut back while they were resting over the weekend.  Some horses tie up when they become excited, at an event, breeding, or traveling.  Other horses develop the problem when exercised.  Occasionally, you may run into the horse that ties up for no reason you can detect.

Moderate to severe cases are not hard at all to diagnose.  The hard painful muscles and stiffness in the rear limbs are easily seen,  but mild cases may present a decreased performance or a slight lameness originating in the hind end or back.  In cases of possible tying up, the diagnosis can be confirmed with blood tests where you will look for increased levels of muscle enzymes (SGOT/AST and CPK).

Possible Causes:

There have been many proposed causes for tying up.  The different histories and varying treatments that horses respond to strongly suggest that we are looking at several different diseases.

Some proposed causes are:

*Altered carbohydrate metabolism –  Recent work has identified that abnormal carbohydrate metabolism is a cause in many breeds of tying up.

*Hypotension and Electrolyte imbalances –  Horses which tie up during or following exercise frequently have electrolyte imbalances.  These imbalances cannot be diagnosed with simple blood testing.

*Lactate build up

*Too little oxygen getting to the muscles

*Hypothyroidism

*Vitamin E / selenium deficiencies

Diagnosis is not generally complicated, except in mild cases which may resemble generalized stiffness or founder.  The muscle enzymes CPK and AST are immediately elevated during a tying up episode and shortly after.  Strenuous exercise could elevate these enzymes up to 4 times normal while most tying up episodes result in a 10 times rise or greater.

Treatment:

First aid will depend on the severity of signs.  When just a little stiffness occurs, hand walking may help a horse loosen up, BUT it has been suggested that walking may be harmful but many mild cases have improved by being walked.  Banamine (Flunixin) should be given for pain.  Acepromazine (1 to 2 mg. /1000 lbs.) will be helpful to relax the horse and increase peripheral perfusion.  If the stiffness is severe, the recommendations are to NOT move the horse.

Many severe cases are associated with intense exercise.  If dehydration or electrolyte imbalances are possible, plenty of IV fluids should be used to correct these problems.  Potassium plays a key role is maintenance and recovery.  Corticosteroids do make sense for early treatment to help prevent further cellular damage

Muscle relaxers such as dantrolene and methocarbamol are a good choice for preventative treatment.