Tying Up

by Rebecca Colnar. http://www.manepoints.com

It's called tying up, azoturia, Monday morning sickness and, by veterinarians, myopathies or myositis.

Whatever the name, though, most riders are familiar with the problem. You are trotting along vigorously when suddenly your horse stops, appears to be in distress, and is unable to move. What's going on?

Lactic Acid

"Your horse is suffering from exercise-induced myositis, or tying up. Tying up is often caused by excessive levels of lactic acid building up in the muscle and blood," says Dr. Bill Vandergrift, president of EquiVision, Inc., a company involved in equine nutrition consulting services.

"The excess acid level reduces cellular enzymes and blood pH and interferes with the normal function of cellular enzymes and the sodium pump." Explains Vandergrift.

"The resulting acidic condition means cells cannot derive energy by metabolizing important nutrients such as carbohydrates, fats and proteins. This, in turn, means the muscle cells cannot perform the normal sequence of contraction and relaxation during exercise. The muscle cells consequently enter a state of suspended contraction, or tie-up."

Vandergrift says the classical type of tying up (azoturia caused by excessive grain intake) is easy to manage.

"The horse that's susceptible to tying up should be fed as much good quality hay and roughage as he wants, with the minimum grain needed to maintain the horse's desired condition and energy level of the horse" Vandergrift advises. Horses being ridden only once or twice a week or less should not be fed more than four pounds of grain per day.

While the chemistry of azoturia is understood, the factors contributing to it are not as clear. "Besides consuming too much grain for their activity level, may horses tie up do so as a result of dehydration, glucose depletion, electrolyte imbalances, mineral and vitamin deficiencies and hormonal fluctuation," says Vandergrift.

Not understood

Fillies are more susceptible than colts to tying up.

Although the reasons are not completely understood, it's believed that fluctuations in estrogen levels affect the requirements for certain minerals and vitamins, as well as the activity of other metabolic controlling hormones such as thyroxin.

"Feeding a horse to reduce the incidence and severity of tying up should include improving glucose levels, increasing thyroid function, increasing hydration and blood volume, balancing electrolyte levels, and feeding minerals and vitamins," says Vandergrift. "Feed a moderate level of high-quality grain that's easily digested in the horse's small intestine."

For most horse owners, this advice is simple to implement. Horses should not be fed more than 15 pounds of grain daily, and they shouldn't be fed more than five pounds of grain at any one time, warns Vandergrift.

He says that if the horse needs more than 15 pound of grain per day to maintain adequate body weight and condition, a better forage should be selected. Vegetable oil can be added to the diet (up to 1.5 cups per day) to provide more calories without feeding excessive amounts of grain. Or, adds Southern States equine veterinarian Dr. Ken Kopp, consider using a higher-fat balanced ration.

Beet pulp

"Feeding two or four pounds of shredded beet pulp in the horse's ration works very well," says Vandergrift. "Beet pulp contains more calories per pound than the best alfalfa, yet at the same time, it contributes to the horse's requirement."

(Southern States' Target Feed, adds Dr. Kopp, "is balanced feed with beet pulp as its primary ingredient. Feeding a balanced beet pulp feed is more advisable than feeding an unbalanced raw beet pulp.")

Vandergrift notes that minerals are also a factor, since dietary electrolyte balance has a significant effect on blood glucose levels and pH levels during exercise.

Dietary electrolyte balance is affected by the concentrations of potassium, sodium and chloride in the horse's diet.

"Sodium deficiencies are commonly found in the diets of horses that have a tendency to tie up," says the equine nutritionist.

Low dietary sodium concentrations result in reduced dietary electrolyte balances which in turn stimulate excessive calcium excretion and reduced blood glucose and pH levels. "A sodium deficiency has a great effect on the horse's ability to metabolize glucose efficiently, as well as his ability to relax and contract muscle. So, lack of sodium is really a double-whammy in causing horses to tie up," Vandergrift says.

Hormonal factors

Horses that exhibit low thyroid hormone levels are also more prone to tying up than others.

"Recent research has indicated that horses fed excessive amounts of protein may suffer from low thyroid function," says Vandergrift.

"Therefore, if your horse tends to tie up, try to meet the horse's nutrient requirement without providing excessive amounts of protein - that is, provide 100 to 120 percent of a horse's daily protein requirement while providing higher magnesium intake."

In practical terms, that means feeding a grain mix containing 10 percent protein with a magnesium level of at least .3 percent.

Other factors

It has also been proven that body water levels, blood volume and stamina levels are all related to azoturia.

"Adequate water intake is a real concern for performance horses," Vandergrift says. "Simply ensuring that an adequate amount of water at the desired temperature is provided can go a long way to improve the hydration level of horses and prevent muscle fatigue."

However, water retention must be improved for horses to effectively increase their blood volume levels, This can be done by ensuring that adequate amounts of salt are provided in the horse's diet each day, according to Vandergrift. Use free choice salt or add electrolytes to the horse's grain mix.

Trace mineral and vitamin intakes can also play a central role in reducing the incidence and/or severity of tie ups. These substances can detoxify the horse's body by removing free radicals that are produced at substantial levels when the horse exercises.

Vandergrift says, "Major minerals that reduce the production of free radicals are zinc, copper, selenium, vitamin E, vitamin A and vitamin C. Proteinated or chelated minerals are superior in reducing freed radicals also."

Performance horses should get more vitamins and minerals than the average horse.

"However," he says, "be careful with iron supplements. Excessive iron can actually stimulate freed radical production levels. Therefore, use caution when administering high iron supplements, such as blood tonics, to horses that have tied up in the past."