Azoturia, or Equine Rhabdomyelosis, is a muscle condition that causes cramping. It is also sometimes referred to as Tying-up Syndrome, Monday Morning Disease, Myositis, or Setfast. In the most severe cases, extreme cramping can damage the muscles which can cause the release of myoglobin to the kidneys and then into the urine. The urine will turn a dark reddish color if this has happened. In most cases, horses will show signs of azoturia by shortening the stride and then eventually cramping until they are immobile.
Azoturia is not totally understood and there are different theories as to why it occurs. It has been proven to occur more in fillies and mares than geldings and stallions and it is believed that this is a hormonal effect caused by the horse coming into heat. It is widely believed that azoturia is a result of working a horse too hard after it has had days of rest on a full diet. This causes a build up of lactic acid which in turn causes local tissue damage and constricts blood flow to the muscle tissue.
Azoturia often occurs towards the end of the workout. The horse might begin to drag his back legs and his rear muscles will become very tight and sometimes balled up to the touch. It is important to check the horse's pulse and respiratory rate. If he is perspiring and breathing heavily he probably has a more severe case of azoturia.
In mild cases, the horse should be kept warm and massaged, and be encouraged to drink until his muscles loosen. In the following days he should be walked regularly and not put back to total rest. In more severe cases, the horse may need fluids given orally or intravenously. Steroids can be given in the early stages of azoturia. If the horse is showing signs of intense pain, he should be given pain killers.
To help prevent azoturia, horses should stay on a well-balanced diet with controlled exercise. When the horse is working harder, he should take in higher calories and protein. When he is working less or is inactive, his feed intake should reduce as well. Feeding a horse Vitamin E and selenium, electrolytes, sodium bicarbonate, thyroxine, thiamine, acepromazine, Dantrolene, phenytoin, and diazepam are believed by some to help reduce the chances of azoturia, but they are not medically proven to work. Horses seem to benefit from eating grass and also from being ridden while out at pasture.