“Tying up” or exertional rhabdomyolysis refers to muscle stiffness and pain after exercise. It can occur sporadically or chronically. Sporadic “tying up” is due to a temporary problem in muscle cells caused by fatigue, heat exhaustion, or electrolyte imbalance, and can occur in any breed. Chronic or recurrent “tying up” is an inherited problem with the way muscle cells use calcium, and is mainly seen in Thoroughbreds, Arabians, and Standardbreds.
Horses with the sporadic version of “tying up” may have imbalances in their diet or inconsistencies in their training program. These issues may be corrected through the use of dietary supplements, a change of feed, or a more regular training schedule. When modifying the diet, particular attention should be paid to whether or not Vitamin E and selenium supplementation is necessary. The horse’s electrolyte requirements should also be considered.
Horses with the chronic version of “tying up” should also have their diet examined for the nutrients mentioned above. In addition, research has shown some benefit to supplementing with the minerals Chromium and Magnesium. There are also anecdotal reports of benefit from adding Dimethylglycine (DMG) to the diet.
The signs of “tying up” can range from mild to severe and include the following, all associated with exercise:
Medical treatment for a horse suffering from “tying up” includes keeping the horse hydrated by administering fluids, relieving the horse’s anxiety with tranquilizers, and making him more comfortable with pain relievers such as bute (phenylbutazone) or Banamine® (flunixin meglumine). In addition, Robaxin (methocarbamol) and Dantrium (dantrolene) are muscle relaxants frequently prescribed for this condition.
The recommended diet for a horse with recurrent “tying up” has less starch and more fat, which can be accomplished a number of ways. First, make sure the horse receives 1.5 – 2.0% of his body weight in forage daily. Then, replace some or all of his grain/sweet feed with a commercial product specifically developed with fewer nonstructural carbohydrates. Depending on the product used, additional fat in the form of rice bran, oil, or powder may be necessary. In addition, electrolytes are recommended in the form of plain salt or commercial mixtures containing sodium, potassium, and chloride for horses in heavy training/competition or in hot, humid climates.
For some horses, the combination of stress and exercise leads to an episode of tying up. Use the following suggestions from the University of Minnesota College of Veterinary Medicine to avoid "trigger factors" in nervous-type horses: