Exertional Rhabdomyolysis Syndrome is a muscular condition that causes muscle cramping in stabled horses (Waran, 2003). It is also known as Monday morning disease, tying-up, azoturia and set fast. It mostly affects well muscled horses and horses in routine work schedules. The development of ER is mainly influenced by factors such as exercise routines, age, temperament of the horse and diet.

Causes

The cause mainly occurs if a horse has been following a strict exercise routine but then is given a rest day without the reduction of its working feed (Taylor et.al. 2010).

Although the pathogenesis of the condition is unclear, there have been many observations as to understand the condition better. For instance, Carlström showed that there was a build up of glycogen in the body during the rest period given to the horse after a working session and the release of the glycogen was the result of the spasm or paralysis of the muscle (Rooney and Robertson, 1996).

The type of feed also has an effect on the outcome as it is observed that feeds with high carbohydrate rate is a factor in the large amount of glycogen which builds up in the muscles (Rooney and Robertson, 1996). Horses are herbivores and in their natural habitat they gain all their glucose need via their cellulose digestion, but the modern day diet includes high levels of carbohydrates, stimulating glucose absorption which is then stored in the muscle (Rooney and Robertson, 1996). The stored glucose would usually be burned off for energy in a working horse.

Symptoms

•    Stiff gait and reluctance to move
•    Hindquarters firm to touch
•    Muscle tremors
•    Excess sweating, causing loss of electrolytes
•    Increased respiration and heart rate
•    In severe cases the urine will appear dark red, due to leakage of muscle protein myoglobin.

First Aid

If the horse shows signs of stiffness while at work, it should be dismounted immediately and put to rest. The horse should be kept warm with rugs or hot packs should be applied on effected muscles (Orsini and Divers, 2008). It should be encouraged to take in fluids, this will reduce muscle breakdown. To recover electrolyte loss a salt block could be given. If any of the clinical symptoms occur while the horse is worked outside or away, it should not be ridden back but transport should be used. The vet should be informed and the horse should be kept under close watch.

Aiding Recovery

The main aim of recovery and treating the condition should be to reduce the pain and anxiety in the horse. Horses should be put to stall rest and on a hay diet for a couple of days (Valberg, 2006). This could be accompanied with a small paddock turnout for a couple of hours a day if available (Valberg, 2006). While horses acutely affected should be moved as little as possible as movement may worsen the pain (Ulman, 2000).

The horse should be brought back to work gradually, starting with 5-10 minutes of in hand walking (Valberg, 2006). The training program must be laid out appropriately for the horse as to not put it under working stress and preventing azoturia doing so (Valberg, 2006).

Rearranging the diet is, again, one of the preferred and main methods of controlling and aiding the recovery of ER (Valberg, 2003).

Prevention

•    Warm up before exercise to decrease chances of ER
•    Rest periods during training sessions to relax muscles
•    Balanced diet with vitamins and minerals
•    Accessible fresh clean water
•    Salt blocks to prevent electrolyte loss

A combination of a well-designed training regimen with a nutritionally balanced, which has adequate vitamins and minerals, are the main aspect of aiding recovery (Valberg, 2003).

List of References:

1.    Diagnostic Techniques in Equine Medicine, Frank G.R., Tim J. Brazil, Mark H. Hillyer, Second Edition, Saunders Elsevier, 2010.
2.    Equine Emergencies: Treatment and Procedures, James A. Orsini, Thomas J. Divers, Third Edition, Saunders Elsevier, 2008.
3.    Equine Pathology, James R. Rooney, John L. Robertson, Iowa State University Press, 1996.
4.    The Welfare of Horses, Edited by Natalie Waran, Kluwer Academic Publishers, 2002.
5.    Exertional Rhabdomyolysis, S.J. Valberg, International Veterinary Information Service, 2006.
6.    Equine Exertional Rhabdomyolysis : Management of Sporadic Exertional Rhabdomyolysis, Stephanie Valberg, American Association of Equine Practitioners, 2003, revised 2011.
7.    Summer 2000 Newsletter: Equine Exertional Rhabdomyolysis, Katherine Ulman, edited by Janice Lacey, 2000.