“TYING UP” (RHABDOMYOLYSIS)

Tying up is a relatively common condition which affects the muscles of the horse’s hindquarters and back. Inflammation of these muscles causes pain and stiffness. It is a complex condition and one that is not completely understood. It is usually seen in horses on high energy diets after a rest from their normal exercise routine. In some individuals that appear to be particularly susceptible, notably fillies, even a reduction in exercise for one day can result in the horse becoming ‘tied up’ on resumption of normal exercise. There also seems to be a temperament/stress component with nervous or highly strung horses being more frequently affected.

In mild cases of tying up horses will just appear ‘stiff behind’ after exercise. Usually both sides of the body are affected equally so the horse may not actually appear lame. In more severe cases the horse may be reluctant to move and show signs of pain such as sweating. Some may be thought to have colic. Very severe cases may be unable to move and may even collapse.

If you suspect that your horse is ‘tied up’, stop exercise immediately and dismount. If the horse can walk, return to the stable. In general it is best not to keep your horse walking as this may worsen the muscle damage. Moderate to severe cases should be seen by us as soon as possible. Severe cases may require intravenous fluids and intensive supportive treatment. A blood sample can be collected to measure muscle enzymes to confirm the diagnosis and to determine the severity of the muscle damage. Follow-up blood samples may be used monitor response to treatment and confirm when it is safe to resume exercise.

Initial treatment consists of anti-inflammatory medication and rest. Muscle breakdown products are toxic to the kidneys so it is important to ensure that the horse receives ample fluid either via drinking water, stomach tube or intravenous fluids in order to “flush” the kidneys. Use of vitamin E and selenium products has long been advocated to help stabilise muscle cell membranes. Remember that the popular product “Kynoselene” contains the prohibited stimulant heptaminol and an adequate withdrawal time must be observed. The tranquiliser acepromazine is also of use both to relax nervous horses before work and its action as a vasodilator is also believed to improve blood flow to muscles. Acepromazine is also a prohibited substance and mustn’t be used too close to competition.

Ensure that your horse’s diet is providing the appropriate amounts of energy, protein, vitamins, minerals and importantly, electrolytes for the job you are asking it to do. On ‘easy’ days, or if the horse cannot be worked for any reason, reduce the amount of high energy feed (especially grain) your horse receives to reflect the reduction in exercise. Ensure all horses gets some exercise every day, even if this is only being turned out to a paddock or hand walking.

If your horse has ‘tied up’ it is important to give the muscles time to recover. Recovery can be monitored using blood tests. A gradual return to exercise after recovery is recommended so that there is no sudden increase to trigger another episode of the condition.
If your horse has a recurrent problem with tying up, we can attempt to determine if there are electrolyte, mineral or dietary imbalances which may contribute to the condition and require correction. Generally these horses do better on decreased carbohydrates (e.g. oats, barley) and an increased proportion of energy being obtained from fat (e.g. canola oil). Be sure to introduce fats gradually and add additional sources of vitamin E to the diet.