We all know that muscles are critically important for the mechanics of performance, so of course, conditions related to the muscles are top of mind for performance horse owners.
One such condition, which no horse owner ever likes to see, is rhabdomyolysis, commonly referred to as ‘tying up’ or Monday morning disease.
Tying up in horses is characterized by muscle pain and cramping due to the breakdown of striated muscle cells, and though the condition can stem from several different causes, it is most commonly associated with exercise.
It’s important to understand the possible implications of tying up--it can be performance-limiting or even career-ending for some horses--so knowing what you, as the horse owner, can do to prevent it in the first place is crucial.
What causes tying up
When tying up results from exercise, it is technically known as equine exertional rhabdomyolysis (ER), and it can occur infrequently (sporadic ER) or on a recurring basis (recurrent ER).
Due to the strenuous nature of their work, race horses are commonly affected by ER. In fact, equine surgeon and FullBucket co-founder, Dr. Keith Latson, says that 8 out of 10 muscle diagnoses in the race horses he sees are cases of sporadic ER.
Sporadic ER often results from:
- Muscle trauma;
- Exhaustion; and
- Dietary/electrolyte imbalances (especially high-carbohydrate diets, insufficient vitamin E and selenium, or electrolyte imbalances).
Equine recurrent exertional rhabdomyolysis (RER) is believed to be caused by an abnormality in the regulation of muscle contraction and relaxation and may be triggered by excitement. This form of chronic tying up is usually seen in Standardbreds and Thoroughbreds, and interestingly enough, occurs most commonly after low-intensity exercise.
What happens when horses tie up?
The signs of tying up in horses are usually easy to spot, as the animal will be very uncomfortable and often reluctant to move. The most common symptoms of tying up in affected horses include:
- Firm, painful muscles over the loin and croup along the top line, as well as the gluteal muscles;
- Excessive sweating;
- Quick, shallow breathing;
- Rapid heart rate; and
- Muscle tremors.
But what exactly is going on inside the muscle cells when these symptoms occur? Dr. Robert Franklin, equine internal medical specialist and Latson’s business partner at Fullbucket explains:
“The problem whenever we deal with rhabdomyolysis is that the muscle cells can fail and whenever they fail, they will actually rupture and release their contents into the bloodstream.”
Latson notes that changes in the horse’s urine will usually be present as well, and the color and consistency may range from light red-tinged urine all the way to thick, red urine with the consistency of coffee grounds.
“When it gets to this extreme, it is a medical emergency,” says Latson, “because now we’re talking about the health of the kidneys, as well as many other body systems, not just some cramped muscles that need time to recover.”
Franklin notes that horses aren’t the only ones who can experience rhabdomyolysis--people can, too--and he goes on to explain about the filtering component in the kidneys, known as the glomerulus.
“The glomerulus works like a swimming pool filter to separate things, and that filter gets clogged by the muscle pigment called myoglobin. Myoglobin just stops the filter and then you can imagine (in the pool analogy) that all the algae and bacteria just overgrows. You can’t balance any of the electrolytes in the pool, and the same thing happens in the blood. If a horse can’t eliminate the toxins its body produces, and they can’t balance the water or electrolyte load, the patient can fail.”
What to do when a horse ties up
Though not every incidence of tying up is as severe as what is described above, you still need to treat it as such. If you suspect your horse is tying up, immediately stop any exercise and call your veterinarian.
While waiting, offer the horse water but don’t force him to move. You can gently massage the back and hindquarter muscles if your horse will tolerate that. If you need to transport the horse to a veterinary hospital, walk him slowly to the trailer, stopping for breaks as needed. Add deep bedding in the trailer in case the horse needs to lie down during transport.
Your vet will take a blood sample in order to determine the extent of the muscle damage, and two different muscle proteins are typically measured: creatine kinase (CK) and aspartate transaminase (AST).
Franklin says he usually treats these horses with pain relievers, electrolytes, IV fluids, muscle relaxers, and oftentimes, vasodilators.
After immediate treatment, stall or paddock rest is generally recommended, along with some hand walking for the first few days after the episode. Horses with mild episodes of tying up can likely return to gradual work after a few days, but horses who have suffered more severe tying up episodes may need additional time off.
Once horses are back in training, it’s recommended they get daily exercise with a prolonged warm up period, as CK levels can actually increase on days off.
How nutrition can help tying up in horses
For horses prone to recurrent exertional rhabdomyolysis, stress management and proper nutrition are key. Allowing these horses to live as naturally as possible with companions can help to keep stress levels in check. Owners should also ensure that the horse is getting enough salt in his diet; if you have traditionally used a salt block, you might try adding loose salt into his feed bucket instead. A low-carbohydrate diet is often recommended as well.
“We often try a high fat diet for these horses,” says Franklin. “Many companies market high-fat, low-carbohydrate feeds for horses that have muscle problems. That’s because a lot of muscle problems are genetic and related to the storage of glycogen.”
Franklin also explains why Fullbucket’s product, Medical Muscle, is a strategic and effective supplement to consider giving to horses at risk for tying up or simply as a preventative for hard-working horses.
“Medical Muscle is unlike any other muscle supplement out there because of the astaxanthin, along with the L-carnitine and natural vitamin E,” he says. “Those ingredients actually stabilize the muscle cell and do not allow the cell to rupture during times of stress.”
Franklin goes on to explain that astaxanthin has a potency unlike any other antioxidant.
“Astaxanthin is what elite human athletes, especially endurance athletes, use to train, because it accumulates in the muscle cell and staves off the incidence of tying up,” he notes. “It also increases endurance, by allowing the cell to perform at a high level for a longer period of time.”
Massage, stretching, and other modalities that help to relax the muscles can be beneficial for horses with RER, but more importantly, keeping them on a regular exercise program and not expecting them to perform at a level they haven’t trained for.
“Our goal with managing tying up is to prevent it,” says Franklin. “And that’s where resiliency and the adaptation to increased levels of training really comes in. We want to steer towards wellness and to widen that band of resiliency and exercise tolerance.”
In the next segment of this series, we’ll focus on the genetic component in tying up--polysaccharide storage myopathy (PSSM)--so stay tuned.