A horse who is tying-up is experiencing severe muscle cramping after exercise. It’s not a single disorder with a single cause, however. It may have multiple causes at its root, and determining the causes and the solution can be a challenge. The first step is to classify the problem as sporadic or recurrent.
Sporadic tying-up means the horse had a single episode, or long periods of time between episodes, rather than frequent repeated problems. With sporadic tying-up, there’s usually an external management-related cause, while horses with regular tying-up may have an inherent biochemical disorder.
In any case of tying-up, you likely have more than one risk factor operating. Even when the horse has an underlying metabolic problem at the root, it can be external factors that push him over the edge, or make the problem worse.
Your first step is to identify and fix any external factors, then to get your veterinarian involved for a detailed diagnostic workup if the problem persists, including risk factors.
Overexertion is often involved. A single episode of very heavy work in an unfit horse can cause muscle damage and soreness, but this may not be obvious in the typical tying-up scenario where the pain and cramping will occur while the horse is still working/exercising.
More commonly, it will be a horse that’s in a heavy training program and being pushed along faster than it should. Every time the horse is worked hard there’s more damage to the muscle, until another hard work or the addition of a second risk factor like dehydration and electrolyte imbalances pushes him over the edge.
Too little exercise can be involved, too. Horses that are worked hard but for short periods of time, like racehorses, and spend the rest of their time in the stall are at increased risk. Tying-up is most likely to occur when the horse is racing-fit. After a hard work out, the muscle normally adapts by increasing its stores of glycogen.
Recent research has identified two forms of glycogen — proglycogen and macroglycogen. Proglycogen is formed rapidly and first. It’s a much simpler structure that is more easily and quickly broken down. When a hard-working horse misses a day of work, glycogen continues to accumulate. This easily metabolized glycogen may then break down too quickly and the muscle overcontracts. Exertion-related stiffness will be worse in all horses that can’t keep moving around freely.
We tend to think of how often and well we feed our horses as determining how much “fuel” they will have for work, but when the horse is exercising he relies primarily on energy that is already stored in the muscle as glycogen.
Both working at speed and working for prolonged periods of time places tremendous drains on these stores. It can take three days or more for the glycogen level in the muscle to return to pre-stress levels, and low glycogen stores predispose to cramping and muscle damage.
Severe electrolyte imbalances can cause tying-up, but this is only likely to be a major cause in horses that work for a prolonged period, e.g. endurance. Sweat and electrolyte losses are also sizeable for horses working shorter periods but intensely. If not supplied with adequate salt and a mineral-balanced diet, and given at least three days between hard works, electrolyte deficits can worsen until they reach the point they can at least be a contributing factor to tying-up.
Finally, a variety of mineral, vitamin, and protein deficiencies, in addition to electrolytes, influence how well the muscle handles exercise. While it would take extreme deficiency states for any of these nutrients to be solely responsible for severe tying-up, they can easily be the determining factor in whether or not a horse under heavy exercise stress, or dealing with an underlying metabolic problem, will tie up or not.
Of particular importance are calcium, magnesium, selenium, the B vitamins, vitamin E and vitamin C. L-carnitine, which is both an antioxidant and an important cofactor in energy generation, may be deficient in unfit horses undergoing training. The protein in muscle is heavily composed of branched chain amino acids, which the horse must get from his diet. Turnover of these amino acids is high in exercising horses, even more if there is muscle damage.
While tying-up takes many people by surprise, there can be early warnings if you’re alert to them: low-level muscle problems that haven’t caused severe pain/cramping yet often show signs of irritability, less interest in work, possibly decreased appetite, and overall stiffness when working. These are all nonspecific indicators of pain.
More specifically, you may notice the horse is not muscling up as expected, or even losing muscle mass. Most revealing of all is the muscle tone. Even fit horses with well-defined muscles should feel soft and pliable on palpation. The pectorals (chest), triceps (above the elbow) and quadriceps (above the stifle) should be relaxed and soft at rest, with a consistency similar to a pot roast. Rump and back muscles will normally have a bit more tone even at rest but should still be easily indented. You should be able to easily insert your fingers to a depth of about one inch in the space between the neck muscles and the front edge of the shoulder.
Tying-up tends to be more common during both very hot and very cold weather. In the heat, muscle function can be compromised by overheating (a risk for horses not properly acclimated to the level of work under high heat conditions), mild dehydration and electrolyte losses in sweat, especially sodium and potassium.
What’s going on with cold weather isn’t as clear. Severe chilling, to the point the body temperature drops, interferes with blood delivery and energy availability in the muscles, but it’s unlikely this is a factor in healthy horses.
Insufficient warm-up time before starting strenuous exercise, cold-induced spasm of muscles that were already “strained” but had not been obviously symptomatic before, or a nonspecific stress reaction triggered by cold weather precipitating the symptoms in a horse that has an underlying low-level metabolic problem are possibilities.
General support products can be used for horses with both sporadic and recurrent problems with tying-up, and we’ve listed some good representative products in our chart.
Much of this support surrounds basic good nutrition, which is important even if your horse never ties up. If your favorite product isn’t included, compare its ingredient levels to the ones we’ve listed here, which have good levels in them.
For horses with repeated episodes of tying up, it’s imperative to get a complete diagnostic work up to identify any underlying disorders so that they may be treated most effectively. We’ve included products that we find offer good support for tying up that has been traced to specific causes/deficiencies.
Contact Your Local Tack Store Or: Peak Performance Nutrients, www.peakperformance nutrients.com 800-944-1948; Uckele Health and Nutrition www.uckele.com 800-248-0330; Kentucky Equine Research www.ker.com 800-772-1988; Buckeye Nutrition www.buckeyenutrition.com 330-828-2251; Equine Gold www.equinegold.com 800-870-5949; Equine Racing Systems www.equineracing.com 360-837-3700; Med-Vet Pharmaceuticals www.unitedvetequine.com 800-328-6652; Vita-Flex www.vita-flex.com 800-848-2359; Finish Line www.finishlinehorse.com 800-762-4242; Farnam Companies www.farnamhorse.com 800-234-2269.
Also With This Article
Click here to view ”Devise Your Plan.”
Click here to view ”Tying Up First Aid.”
Click here to view ”Determine What Your Horse Needs.”
Click here to view ”Choose The Product That Fills Your Horse’s Needs.”
Click here to view ”Recurrent Tying-Up Causes.”