Causes of Tying-Up
Tying-up can occur due to multiple problems, some of which may be inherited or due to the horse's sex or personality. Many do require veterinary management and medications, but others can be avoided with proper management and conditioning.
Overexertion/under-conditioning: Working your horse longer or harder/faster than he is fit to do can cause sufficient muscle damage to result in obvious cramping and elevated muscle enzymes. Cramping, stiffness and reluctance to move may also be seen two to three days after a bout of heavy exercise, when delayed muscle soreness sets in.
Electrolyte imbalances/dehydration: This is most likely to be a problem for hard-working horses competing in hot weather, but even horses doing less intense work for prolonged periods in the heat can get into trouble if they don't have adequate water and electrolyte intake. Adequate salt intake is of prime importance, with potassium, too, for horses not eating normal amounts of forage. Incorrect dietary intakes of calcium and magnesium may also contribute.
Overheating: Overheating usually occurs in conjunction with overwork and/or electrolyte disturbances and dehydration but, under conditions of high heat and humidity, it may be the major factor. Skeletal muscle damage is a component of heat stroke.
RER (recurrent exertional rhabdomyolysis): The disease RER is normally found in Thoroughbreds and Standardbreds and is caused by abnormally rapid release of calcium into the cellular fluid from its storage depots inside the cell. Free calcium ions in the cell trigger contraction. The muscle contracts so rapidly and forcefully that there is no energy left for it to relax again. Nervousness, female and young age are reported to be factors in Thoroughbreds.
The horse working prolonged periods in the heat should be given about 4 oz./day of salt, which translates into 45 grams of sodium. In the 3 oz. of electrolytes he's getting (above) to help cover potassium, there is 6.6 grams/ounce of sodium so a total of 20 grams (rounding from 19.8), leaving you short 25 grams of sodium. Salt (sodium chloride) is 40% sodium, so you still need 2.2 ounces of plain salt on top of the electrolyte product. Do you see how easy it is to get into trouble with electrolytes if you count on a supplement to get the job done? That's not what they're meant to do.
Calcium and Magnesium: The working horse should get adequate, but not excessive, calcium to match his weight, age, work and growth requirements. Alfalfa, for example, can cause problems because of its natural high calcium. If you have sporadic tying-up problems, this is an area you want to have investigated. Some horses also do better with higher-than-average intakes of magnesium.
MANAGEMENT
Controlling tying-up is mainly a case of paying attention to management, fitness and diet.
Rule #1. Never work the horse beyond the level of activity you know he can handle without becoming fatigued. Condition your horse for your level of activity and your competition level carefully. Most horses enjoy working and can easily be encouraged to overdo it. A horse that has pent-up energy from being confined, or one that is in training and just reaching the point where they are starting to feel fit and on their toes, may fool you with their level of eagerness.
Rule #2. Regular daily exercise is important in horses prone to tying-up. "Monday morning disease" is one of the older names for tying-up, because it commonly struck work horses on Monday morning, after having been stalled and doing no work the day before. Daily exercise is also an effective way to control PSSM. It has been found that PSSM horses exercised daily for a month had almost normal post-exercise muscle enzymes even without fat supplementation. PSSM horses kept on 24/7 turnout also had muscle enzymes return to normal without feeding any fat.
Very fit horses are also more prone to tying-up if they miss their regular work outs. In addition, horses that are in training for speed work often go through a similar high risk period when they reach the point where they are beginning to perform work at speeds that demand high anaerobic generation of energy. The reason for this isn't entirely clear, but the solution is the same: Don't skip work days.
Rule #3. If a fit horse is not going to get his regular exercise, drastically cut or even eliminate the grain ration on that day. Interestingly enough, horses that are stall confined for one or two days are at risk of tying-up, but if three days or longer it's much less of a problem. This suggests there may be a factor of accumulation of a rapidly burned fuel, possibly short chain glycogen molecules. Adjusting the intake of soluble carbohydrate is another helpful strategy.
Rule #4. Pay attention to electrolyte and mineral intake to take electrolyte imbalances and dehydration out of the picture. When working for prolonged periods in the heat, don't invite trouble by ignoring your horse's water and electrolyte needs. A horse eating at least 10 pounds of hay before and over the course of the day's work, with normal hay intake the day before, probably won't need supplemental potassium. However, if it's less than that, you may be wise to use one a good electrolyte rather than plain salt.
Deficiencies and imbalances in calcium and magnesium can also contribute to muscular irritability and cramping. Excessive high calcium is as bad as too low and may be worse since it interferes with the body's ability to rapidly mobilize calcium from bone when needed during exercise. Horses vary widely in their sensitivity to magnesium intakes, but when magnesium is too low you can see muscular fasiculations, elevated muscle tone and elevations in muscle enzyme.
Rule #5. If the horse has recurrent episodes, get a diagnosis so you know how to proceed. When a horse has repeated episodes of tying-up and external factors have been eliminated as possible causes, you really need to know what you're dealing with. Muscle biopsy will confirm a diagnosis of RER vs. PSSM.
BOTTOM LINE
For horses prone to tying-up, a reduced carb diet is wise. We suggest considering Alam, Re-Leve or Low Starch, depending upon what is available in your area.
All hard-working horses require 1 to 2 oz. of plain salt daily, plus an electrolyte balanced to sweat losses. Our favorites are Perfect Balance and ExerLyte. For added control with horses prone to tying up, we would reach first for Tie Free 24 , which covers the major nutritional bases.
