Tying-up: Complicated syndrome, simple management
August 2007
The horse industry has recognized "tying up" as a muscle syndrome in horses
for over a century. And there are as many names for this syndrome—Monday morning
sickness, azoturia, cording up--as there are theories why it happens. This article
provides an overview of the most current research about the causes, treatment and
prevention of this disorder, according to the Neuromuscular Diagnostic Laboratory
at the University of Minnesota College of Veterinary Medicine Equine Center.
"Tying up" is an umbrella term describing the pain and cramping of a horse’s
muscles with exercise. Therefore veterinarians refer to the syndrome as "exertional
rhabdomyolysis." There are two forms of ER: sporadic and chronic. The sporadic
form is a one-time event that occurs in otherwise normal horses asked to perform
beyond their current level of fitness. For example, an endurance horse conditioned
for a 50 mile ride might tie up if the weather is particularly hot and humid. A
combined training horse might tie up if moved up a level without additional conditioning.
This form of tying up can be managed by correcting electrolyte imbalances, Vitamin
E/Se deficiencies and conditioning programs.
The second form, chronic exertional rhabdomyolysis, is now separated into
two categories. One category is horses that tie up due to polysaccharide storage
myopathy (PSSM or EPSM), covered in a separate article. The other category is recurrent
exertional rhabdomyolysis (RER), which refers to horses that tie up repeatedly,
and is seen primarily in thoroughbreds, standardbreds and Arabians. In the past,
researchers thought RER may be due to lactic acid build-up in muscles, but more
recent studies point to abnormal regulation of intracellular calcium that makes
muscle much more sensitive to contractions. In thoroughbreds, this abnormality may
be inherited.
The signs of RER can range from mild to severe and include the following, all associated
with exercise:
- Firm and painful muscles over the loin and croup
- Excessive sweating
- Quick, shallow breathing
- Increased heart rate
- Muscle tremors
- Reluctance or refusal to move
- Reddish-brown colored urine
- Lying down/inability to rise
Exercise should be stopped immediately and a veterinarian called if any of the above
signs occur. Diagnosis is based on history, physical examination, bloodwork, muscle
biopsy and possibly other tests. Treatment for a horse suffering from tying up includes
keeping the horse hydrated by administering fluids and relieving the horse’s pain
and anxiety. Depending on the results of the bloodwork, the horse may need to be
stall rested and gradually reintroduced to exercise under close observation.
Preventing episodes of tying up in horses prone to RER consists of managing the
diet, exercise and environment. The recommended diet 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, powder or extruded pellets 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 Dr. Stephanie Valberg to avoid "trigger
factors" in nervous-type horses:
- Position the stall in a quiet area of the barn
- Time of training (first rather than last)
- Turn-out (if available a big advantage)
- Avoid training regimes like holding back at a gallop or intervals that
excite the horse
- Tranquilize before exercise to prevent excitement
- Attention to and treatment of lameness
- Avoid stall rest or lay-up if possible, providing calm exercise if
rested the day before
- If necessary, give medications that affect intracellular calcium regulation,
such as dantrolene orally one hour before exercise.
Tying-up, or exertional rhabdomyolysis, is a complicated syndrome and managing a
horse with the chronic form of it can be challenging. But simple adjustments in
nutrition and lifestyle can prevent episodes of this painful muscle condition in
most horses, and allow them to be kept in training and competition.
Tying Up: Complicated syndrome, simple management
By: Lydia F. Gray, DVM, MA
SmartPak Staff Veterinarian and Medical Director
August 2007
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