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The Balancing Act: water v. electrolytes

Posted: Saturday, December 10, 1994

Electrolytes promote tissue growth and help meet energy needs, but there is disagreement as to when or even if-they should be administered as supplementsIf you were asked to name a single nutrient that is most essential for the horse's well-being, it would have to be water.
Water makes up about 70% of a horse's total body weight. It plumps up the body's cells and bathes them with a supply of essential nutrients. A horse can give up food more easily than he can go without water. A mildly dehydrated horse gets tired more easily and cannot work at his best. The moderately dehydrated horse may show signs of physical distress such as colic or muscle spasms. A severely dehydrated horse, one whose body loses 12%-to-15% of its total water content, can die.
Dissolved in the body's water are electrolytes-electrically charged ions that are essential to the formation of new body tissues, the transfer of energy within cells, and as agents in a multitude of enzymatic functions. Each ion carries a positive or negative charge that pushes the horse's system toward acidity or alkalinity. The horse's body constantly rebalances the amounts of each of these ions (primarily minerals) and water to maintain a neutral solution in a certain concentration.
As the horse sweats, both water and electrolyte levels drop so that the horse's system becomes more acidic (or, more rarely, alkaline) until feed and water intake allows his body to rebalance the water and electrolyte levels to normal.
If specially formulated electrolyte products (which all contain a high proportion of salt or sodium chloride) are added to the horse's diet, the concentration of charged ions in his system increases and thirst will prompt the animal to drink more water as the body attempts to regain that neutral balance. This is one way to get a horse to drink more during hot weather or at times of exertion so that he maintains an optimum level of both water and electrolytes in his system.

When horses need electrolytes
A healthy horse receiving good quality hay or pasture and free-choice salt meets his basic electrolyte requirements. When stress enters the picture, however, that may not be enough. Stress can come from many sources. Besides the obvious physical stress of running a race, just moving a horse from one location to another, changing the animal's companions, altering the daily routine, changing the training regime, even a change in the temperature or humidity, can all stress the horse's body.
Given warm-up times and the stresses associated with changes in daily routine, by the time a horse crosses the finish line on a hot, humid day, it may have lost as much as ten liters of water and the electrolytes in them. The horseman's goal is to replace lost water and electrolytes as soon as possible to bring the horse back to normal.
One important thing to remember about electrolytes is that the horse's body cannot store them. Once the body attains the desired concentration of electrolytes in neutral equilibrium, any excess simply gets processed out through the kidneys. Supplemental electrolytes are absorbed by the horse's system within one-to-two hours and any excess is excreted within four-to-five hours.

Using them
Electrolytes come in powders, pastes, drenches (fluids administered via nasogastric tube), and what racing trainers euphemistically refer to as "jugs" (fluids administered via intravenous drips).
Powder proponents like their ease of administration. Paste aficionados point out they can be sure their horse got the full dose when they administer electrolytes that way. Others like the idea that drenches or jugs ensure that the horse gets extra fluids when the weather is hot and humid.
When it comes to adding electrolytes to their horses' diets, everyone has a theory, but so far, there is not a great deal of scientific evidence to either confirm or disprove the effectiveness of any of them.
Some horsemen give no supplemental electrolytes at all. They believe that a well-balanced diet provides enough of what the horse needs and that even a racing effort does not justify adding something extra to the diet, tubing, or giving a jug. A number of vets agree with them. Given good hay and access to plenty of water, they feel the horse will rebalance his water and electrolytes on his own within 24 hours.
Other horsemen add powdered electrolytes to their horse's rations daily. You never know exactly what things a particular horse will find stressful, they argue, so daily electrolytes are insurance against dehydration that might affect a horse's performance. Conversely, others argue that by feeding electrolytes daily, the horse's body never learns to use its electrolyte supplies (particularly calcium) efficiently. They also point out that feeding electrolytes in excess of what the horse needs is simply a waste of money since they just go out through the kidneys.
A third camp believes firmly in "preloading" electrolytes before a race. Whether with a powder, paste, drench, or jug, extra electrolytes are administered within 24 hours of a race to ensure the horse is fully hydrated and has the optimum concentration of minerals in his body fluids when he heads to the post. Some vets question whether the sudden concentration of salts when preloading may upset the horse's digestive tract temporarily enough to affect performance. While a drench may contain several gallons of water, jugs are generally only half a liter. Some argue that compared to the ten liters of sweat that the horse is likely to lose before he returns to the shedrow, a prerace jug is useless because that half-liter is a figurative drop in the bucket.
Another group holds that the best way to use electrolytes is as a post-race booster to get the horse's water and electrolyte balance back to normal as quickly as possible. Giving electrolyte powders or pastes immediately after a race is one way to accomplish that. Others use jugs administered the day after a race. Some vets argue that postrace jugs are too little too late-too little fluid to make much real difference, too little total electrolytes, and so late after the race that the horse has probably rebalanced his fluids and electrolytes on his own by then.

Checking ingredients
While the horse's body needs many minerals, chloride, sodium, and potassium are the primary focus of electrolyte supplementation because of their volume in the horse's sweat. Calcium and magnesium are next because of their roles in muscle function and enzymatic reactions throughout the horse's system.
Besides these basic minerals, most manufacturers add flavorings to their powdered or paste electrolytes for palatability. Several also add a hefty dose of dextrose or some other form of simple sugar. Besides adding good taste, some people believe that a wallop of sugars can give the horse a little added energy if they are administered just prior to a big effort.
A lot of electrolytes also contain vitamins, other minerals, or amino acids. The biggest problem with vitamin and mineral additives is the possibility of overdosing the horse with certain nutrients if he is also getting them in his regular feed and other supplements.
Water soluble B vitamins will simply pass out through the kidneys and create expensive urine if the horse gets them in excess. Fat soluble vitamins A, E, and K, however, can build up to toxic levels if the horse gets too much of them from multiple sources. Ditto minerals which interact in many complex ways that can be adversely affected by either too much or too little of a mineral in relation to other minerals in the diet.

Summary
Not all electrolytes are created equal. It pays to look at labels and see what you are getting for your money. Comparing labels against the chart estimating electrolyte losses will give you an idea of how much of a product would be needed to restore electrolyte balance. There is an extremely wide variation in the amount of electrolyte per ounce provided by the pastes and powders on the market.
Smart money takes a look at all of the components of a horse's diet and makes sure that he gets what he needs-nothing wanting for a balanced diet and nothing in excess, either. Generally, feeding excess electrolytes as "insurance" will not do anything worse than produce expensive urine. However, if the particular product chosen is also loaded with extra minerals, some careful analysis of the other supplements going into the horse's feed bucket is essential to hitting that target of a balanced diet.

Approximate levels in body fluids