Last Updated on March 15, 2022 by Allison Price
Exertional rhabdomyolysis (tying up) in horses can cause muscle pain, stiffness and excessive sweating. It is also known as muscle pain. It was once known as “Monday Morning Soreness”, but it’s not just the muscle soreness that a person may feel after lifting weights or running, especially if it hasn’t been awhile.
Horse tying up can lead to serious and even fatal complications. This article will discuss the main types of tying up, sporadic or chronic, their underlying causes, the affected breeds, and the symptoms. This article will cover the diagnosis, treatment, and specific diet and management strategies in order to prevent tying up.
What is the purpose of tying up horses?
Since over 100 years, horses have been suffering from severe tying up. Monday Morning Sickness is a term that derives its name from the days when draft horses were only allowed to rest in their stalls for a few hours each day while they were fed their regular ration of grain. When asked to return to work on Monday morning, these horses would often tie up. An episode could be caused by the horse returning to work after an extended period of inactivity on a high-grain diet.
For years, it was believed that tying up was caused by lactic acid buildup in the muscles. It has been proven that horse lactic acid buildup does not cause tying. Scientists and veterinarians now know that tying-up is a syndrome with two types: sporadic or chronic. Each type can have multiple causes.
Sporadic Tieing Up
Sporadic Tying up is when horses experience one episode that is not due to an internal defect but because of something external, such as exercise, diet, or environmental factors. Sporadic tie-up is a problem with muscle cells that can be temporary or permanent. It could be caused by fatigue, heat exhaustion or electrolyte imbalance. It can occur in any age group, breed, gender, or discipline. An example of this is a polo horse that was used in a match before being fit enough to compete, an eventer for three days on a particularly hot day or an endurance horse who has lost electrolytes from a 50-mile race.
Chronic Tying Up
However, “Chronic Tiing Up” refers to an internal problem in the muscle tissue. Although it can still be caused by exercise, diet and management may also affect the condition. This form of tying up can be caused by an underlying defect in the muscle structure or function that causes repeated episodes.
Further complicating matters is the fact that there are many forms of chronic tying up: Recurrent Exertional Rhabdomyolysis, Polysaccharide Storage Myopathy(PSM) Types 1 & 2, Myofibrillar Myopathy and Malignant Hyperthermia.
Recurrent exertional rhabdomyolysis (RER is the term for repeated episodes of tying-up, specifically because of an inherited problem with calcium regulation in muscle. This type of chronic tying-up has been mainly studied in Thoroughbreds but also has been discovered in Standardbreds as well as Arabians. Warmbloods and Quarter Horses are two other breeds susceptible.
The problem with Polysaccharide Storage Myopathy or PSSM is in how muscle cells handle and metabolize the energy. This form of chronic tying-up causes glucose to be stored incorrectly in glycogen and stored in excess in the muscle (PSSM Type 1); or it can simply be stored as “clumps of glycogen” (PSSM Type 2).
Different breeds may display different symptoms. Quarter Horses are more likely to experience classic symptoms such as tying up (muscle stiffness and cramping), with either type PSSM. Other breeds such as warmbloods show signs like poor performance, undiagnosed or vague gait abnormalities and a reluctance of collecting and engaging, loss of muscle mass, progressive weakness and recumbency (lying down).
PSSM is mentioned in this article as it can cause classic tying up in certain breeds. This article provides additional information on the condition, the various types, as well as the diagnosis, treatment and management.
Recognizing when a horse is tying up:
These are the classic signs that a horse is experiencing an episode in tying up. They usually appear shortly after starting exercise.
- Firm, tender muscles in the loin and croup (lumbar or gluteal muscles).
- Shortened, stiff stride behind
- Excessive sweating
- Breathing is quick and shallow
- Rapid heart rate
- Twitching or muscle spasms
- Reluctant to move, or inability to move
- The breakdown of muscle tissue results in reddish brown or coffee-colored urine
- In severe cases, lying down or unable to rise
What to do when a horse is tied up
Horses that are tying up should not be treated as an emergency. Any activity involving the horse must be stopped immediately if it is under saddle or being exercised. Next, contact the horse’s vet and explain the situation. As you wait for the vet’s arrival, make sure the horse is comfortable. If the horse can’t lower his head, remove tack and blanket him with a blanket if it’s too cold. Try to keep the horse still if possible. Make his environment safe and calm by removing any other horses or activities. If the vet gives you specific instructions, such as taking vital signs and administering medication, follow them. At this time, do not give any grain or hay.
The veterinarian will examine the horse and take measures to alleviate anxiety and pain, as well as administer fluids if necessary. The vet may direct the horse to a stall or another confined space. This is because the horse should be restrained for at least 24 to 48 hours. To confirm the diagnosis, blood samples can be taken immediately or later in an episode. A better understanding of an episode can be obtained by looking at the levels of creatine kinase, which peaks between 6-12 hours and aspartate transaminase, which peaks between 24 and 48 hours after an episodes.
How to identify horses that are tied up
The veterinarian might ask questions if this is the first time the horse has had to tie up. A diagnosis of “sporadic tie up” may be made. The veterinarian may recommend the following:
- A balanced and complete diet
- Being able to perform the job being done
- Having no other health conditions, such as lameness or respiratory illness.
- Obtaining optimal levels of VitaminE, Selenium, electrolytes
The vet might also recommend that the horse gradually return to exercise. This could be as simple as hand-walking or paddock turnout. To determine if the horse is ready to work, the vet might perform rechecks on AST and CK blood levels.
The veterinarian might recommend “chronic tie up” if the horse has been tying up for several times in the past. The veterinarian may recommend additional diagnostic testing, based on the horse’s history, age and gender. These extra tests may include genetic assays (tests) of blood or hair and muscle biopsy. Chronic tying up is important as treatment and management of one type, like RER, is different from that for the other types such as PSSM1 and PSSM2.
Recommendations on Horses and Tying Up: Diet, Exercise, & Management
This section will focus on horses who have RER chronic tying up. Horses with occasional tying may just need a balanced nutritional diet that includes optimal levels of vitamins, minerals, and a well-planned turnout, conditioning, and competition schedule. This will help prevent future episodes. Horses with either type PSSM need to be fed a specific diet and follow strict management guidelines.
Horses that are prone to chronic tying-up due to RER tend to do better if the sugars in their diet are restricted. You can make high-quality forage the main ingredient of your horse’s diet, supplement with calories if necessary, or use a low-NSC (not sweet) grain or ration balancedr (not sweet). Stabilized rice bran, high-fat commercial feeds, and oil or powdered fat are all good sources of fat. Here are three things you should consider when adding fat to a horse’s diet with RER:
- Slowly start, allowing the horse’s digestive system to adjust (helping to minimize the chance of loose stool).
- Avoid oils rich in omega 6 fatty acid such as sunflower oil and corn oil
- To help the body metabolize additional fat, provide additional vitaminE
Make sure your horse gets at least 10g sodium each day by topping off with 2 tablespoons table salt when you eat regular meals. Supplementing with sodium or a commercial electrolyte that supplies potassium, calcium and magnesium to horses who are sweating excessively from exercise or high temperatures may be an option.
Exercise and management
Many RER horses may experience a tying-up episode due to stress or exercise. These suggestions are specific to the Thoroughbred horse lifestyle, but can be applied to any horse suffering from recurrent exertional rhabdomyolysis.
- Stall in quiet part of barn
- If you have more horses than one horse, work the first horse.
- As much as you can
- Avoid “exciting” training such as interval training, being restrained from full galop and galloping with horsestreat lameness or other medical issues.
- Avoid stall rest and lay-up, if at all possible
- If you have not rested for a while, do calm exercises
- Ask your veterinarian for muscle-relaxing medication such as dantrolene
Horses who experience chronic RER tying up should be given daily exercise, including turnout, lunging and/or riding. A consistent, calm exercise program is important in preventing horses from tying up.
Horse tying up is not a single condition. It is a combination of several muscle disorders that affect many breeds, ages and disciplines of horses. It can be an inherited condition, which may be confirmed by a genetic test. In other cases, the cause and method of diagnosis are not clear. There are also many ways to prevent or treat it. Riders need to be aware that there are many types of tying up, and each type has its own signs and symptoms. It is important to know when your horse should be contacted by a veterinarian in an emergency and when they are not performing as expected.