Maybe you?ve been out of town for a couple of days on a business trip and are itching to get back into the saddle. After a brief warm-up, your horse enthusiastically picks up the trot. But shortly into your ride, you start to notice that something is wrong.
His neck is stiff, his back is rock hard, and He's having trouble moving forward. The trot slows to a walk, and you hop off, only in time to see your horse freeze in place with a gripping rigor. What is wrong' What is happening' More than likely, he is tying up.
Also known as exertional rhabdomyolysis or Monday morning disease, this musculoskeletal condition is a syndrome known to cause severe muscle cramping (for lack of a better term: ?Charley Horse?).
Literally speaking, ?rhabdomyolysis? means ?striped (or red) muscle break-down.? The condition usually occurs shortly into a bout of exercise and most commonly affects the back and haunches, although it can affect any muscle. In extreme cases, the entire body will be affected.
Horses in an acute stage of tying-up sweat and display muscle tremors. They take short, choppy and uncoordinated steps, if they can move at all. Many just take a ?camped out? stance, looking like they?re going to urinate. The most extreme cases actually lay down.
The sight of a horse in such distress is agonizing. We've included a short video of a horse in the acute stages of tying-up with this article at www.horse-journal.com:?Tying up video.
FIND THE CAUSE. Tying-up actually can occur from more than one cause. The first is the most simple and is called sporadic or acute exertional rhabdomyolysis. This event is usually singular and not due to underlying disease or genetic disorder. Rather, it occurs as a result of either asking a horse to do too much and/or an imbalanced diet.
When a horse is asked to perform beyond his level of physical fitness, muscle damage can occur. Of course, the most common scenarios include high-intensity work (such as a galloping sprint) or prolonged low-to-medium intensity work, such as a long trail ride. Naturally, this form of tying-up is more frequently seen on the racetrack and on endurance rides.
It can occur due to:
- ?Overexertion. Muscle damage causes soreness and subsequent stiffness, as the muscles tear on a microscopic level. If the muscle continues to be exerted beyond its physiologic threshold, it can tense up significantly. ?With this form of tying-up, owners will often report that their horse has red or brown urine, which is due to the damaged muscle being cleared and excreted. If you see this, the condition is serious. Call your vet immediately.
- ?High-sugar diets. They play a role in any form of tying-up.
- ?Electrolyte imbalances. This can cause severe muscle cramping. Horses on long rides that sweat can lose grams of vital electrolytes, especially potassium, sodium, magnesium and calcium.?Click here for our chart on Horse Journal ?Recommended products.
- ?Selenium and vitamin E deficiencies. This is linked to acute exertional rhabdomyolysis. Both elements help battle muscle destruction caused by harmful free-radicals. If either is deficient, muscles may have a greater chance of seizing. Click here for more nutritional/management information.
MANAGEMENT. Caring for basic tying-up involves determining the factor(s) associated with the condition. For instance, if you live in an area where the soil lacks selenium, consider a vitamin E/selenium supplement. Feeding a low-carbohydrate, mineral-fortified pellet?instead of a high-carbohydrate grain?may be helpful.
Feed a good electrolyte supplement every day and provide free access to a salt/mineral block.
Take care choosing your electrolyte, too. Read the label. Many products, while high in the desired minerals, are also high in carbohydrates, which you want to avoid. If the product has dextrose or molasses in it, skip it.
Of course, the availability of copious amounts of fresh clean water goes hand-in-hand with these recommendations.
Finally, gradually train your horse up to the exercise level that you desire. ?Weekend warriors? who ask their horses to do more than they?re physically ready to do are more likely to cause tying-up. ?Click here for What To Do If Your Horse Ties Up and for Information on HYPP.?
DISEASE AND GENETICS. In the grand scheme of things, if your horse just ties up out of the blue, the fixes are relatively simple in comparison to horses that experience repeated episodes.
Unlike the sporadic form, chronic exertional rhabdomyolysis can occur with even minimal exercise, despite a reasonable diet (low-carb, mineral-fortified diet).
To date, there are at least two diseases linked to chronic exertional rhabdomyolysis. Although both of these diseases are well-described, they?re thought to be more yet-to-be identified diseases that cause repeated episodes of tying-up.
1. Polysaccharide Storage Myopathy (PSSM) is a type of chronic exertional rhabdomyolysis that has been described predominantly in draft horses, warmbloods and Quarter Horses. Although no definitive genetic link has been identified, a strong suspicion exists given that the disease exists in significantly higher percentages in certain breeds and family lines within those breeds.
This condition is characterized by two factors. Either one or both of these factors can be present in a PSSM horse. The first is an enhanced sensitivity to insulin. This results in an increased uptake of sugar into body tissues.
The second is over-activity of a muscle enzyme called glycogen synthase. It takes all of that extra sugar and turns it into an energy substrate for muscle called glycogen. Because glycogen synthase is overproducing, glycogen builds up in the muscle, causing it to malfunction and tremor or seize.
Management of PSSM horses involves two ?simple to say but hard to do? factors. The first is that they must have as little sugar in their diets as possible. The second is that they must get moderate exercise every day (a 15- to 20-minute walk warm-up, at least 15 to 20 minutes of walk-trot riding or longeing, and then a cool down).
This helps to ?burn off? any built-up glycogen in the muscle. Studies have shown that when owners combined a strict low-carbohydrate diet with moderate daily exercise, 90% reported episodes of PSSM-related tying-up fell to zero in their horses!
In place of carbs, fat can be supplemented in the diet to maintain weight and energy stores. Canola oil is pure fat and can be added as a top dressing on supplemental feeds. Other forms of fat include supplements that contain poly-unsaturated fatty acids (omegas) or feedstuffs that are high in digestible energy.
2. Recurrent Exertional Rhabdomyolysis (RER) chronic tying-up?s clinical signs are similar to acute rhabdomyolysis, except with this form of the disorder, the horses that suffer from it usually are physically fit. The most common breeds affected include Thoroughbreds, Standardbreds and Arabians.
Once again, there may be a genetic predisposition, but one has yet to be definitively identified. This condition appears to be brought on by excitement or the initiation of intense exercise. Like the other forms of tying-up, RER should be managed by moderate exercise and a low-carbohydrate/higher-fat diet.
Article by Contributing Veterinary Editor Grand Miller DVM.