Electrolyte Primer

Electrolyte Primer

Electrolyte supplements are products formulated with various levels of sodium chloride, potassium, calcium, and magnesium.

Photo: Thinkstock

Not every horse requires supplementation with these molecules that regulate water content, but some steeds do--here's what to consider.

The equine body requires electrolytes; their levels govern functions ranging from muscle contraction to fluid transfer between cells to hydration. The average pleasure horse or light competitor can replenish most of his depleted electrolyte stores with a balanced diet along with fresh water and loose or block salt. However, "extreme athletes" such as racehorses and endurance mounts might require help getting all the electrolytes they need to perform and recover effectively.

It Does Their Bodies Good

There's an essential difference between naturally occurring electrolytes and electrolyte supplements provided to horses, according to Elizabeth Carr, DVM, PhD, Dipl. ACVIM, ACVECC, associate professor of large animal medicine at Michigan State University's College of Veterinary Medicine.

"Electrolytes, in ther simplest form, are just molecules that regulate water content within the body," says Carr. "They're also important in generating electrical potentials (charges) across membranes, which are responsible for nerve conduction and muscle function as well as transport of molecules."

Electrolyte supplements are products formulated with various levels of sodium chloride, potassium, calcium, and magnesium. "Electrolyte supplements are generally pastes or powders supplying some quantity of one or more of these ions that are important for normal functions within the body, and may also include other molecules such as glucose," Carr explains.

When dissolved in water electrolytes become charged particles called ions. Maintaining these ions in the proper compartments inside and outside of the cells is essential for many basic cell functions and physiologic actions.

Carr notes that electrolyte disturbances can alter basic nerve and muscle functions, and they can affect hydration status, gastrointestinal tract pH, and molecular absorption. If you think about how depleted you feel after exertion on a hot, humid day, you'll get a sense of how electrolyte imbalance and depletion can reduce a horse's capacity to perform.

Water and Salt: The Partners of Proper Hydration

We know salty foods, like a bag of movie popcorn, make us thirsty; similarly, sodium is an essential trigger for the equine thirst response.

"One of the clinical signs of sodium deficiency is that horses won't realize they're thirsty," reports Theresa Kujawa, MS, an international equine nutritionist and microbiologist currently living in Thailand. "We think of salt as a function of flavor, but in horses it provides the signal for thirst, and if a horse is sodium-deficient, they're not getting that signal to drink."

There’s a cascade of biological events that happen when a horse isn’t drinking water. "Water is very important in equine digestive health; things don't ferment well in the gut without it," says Kujawa. "In addition, the gut will want to hold on to the water it's got, which means there won't be a flow of fluids throughout the body. In essence, the gut can begin to shut down, with food not being taken up as energy sources. This is when we see colic happen; it's also when you get a drop in pH, an increase in acids and acid-loving and acid-producing bacteria, and a decrease in functionality that can lead to a serious health crisis."

As a nomadic animal, the horse evolved to store and retain water in several areas of the body, such as the cecum and hindgut, drinking deeply upon a return to the watering hole. But today, many horses need sodium supplementation to maintain adequate water reserves, especially low-ranking pastured horses that might have to compete with horses higher up in the pecking order to get to the salt block.

"Unless those low-ranking horses are able to sneak in and access the salt lick, chances are they could become dehydrated and then colic at the first good cold snap, when they're no longer sweating and drinking," says Kujawa.

While the classic signs of dehydration (such as dry mucous membranes in the mouth, skin losing elasticity, fatigue, and weakness) are important to watch for, Kujawa says another indicator of dehydration is a horse that likes to lick salty skin. "Some horses are just comforted by the licking action, but for others excessive licking of salty hands or sweaty skin can be a sign of sodium depletion," she says. For sodium supplementation, Kujawa prefers a plain sodium chloride block or loose salts. In a pinch, an owner can sprinkle plain table salt or sea salt over a nondrinking horse's food to stimulate his thirst.

"It's amazing how easily things can shut down when water isn't present in sufficient quantity," says Kujawa. "It's important to provide fresh water in all seasons, especially when feeding a primarily hay-based diet, because the digestive movement and nutrient absorption are completely dependent upon the presence of water."

Lisa Kemp

The Supplement Shopping Cart

Electrolyte supplements come in block, paste, water soluble, and top-dressing forms, and different applications exist for each. For instance, an owner can give paste electrolytes to an electrolyte-depleted horse that won't eat or drink to stimulate his thirst function and promote recovery. Soluble electrolytes can be provided in a bucket of water for free-choice access, provided a bucket of plain water is also provided.

Whatever the form, taste counts when it comes to selecting electrolyte supplements, according to Theresa Kujawa, MS, an international equine nutritionist and microbiologist currently living in Thailand.

"You should be sure that any loose electrolyte supplement you're using tastes salty, not sweet. It could be different with pastes, which might have flavorings added," she says. "Research has shown that a small amount of dextrose or other sugars improves sodium absorption, but too much sugar can skew the osmotic balance, or levels of fluids both inside and outside the cells, so you're actually throwing the water balance off and creating more problems than you're solving."

If you're new to electrolyte supplementation, first obtain a clean bill of health for your horse from your veterinarian, then check with that vet or a qualified equine nutritionist to determine what is appropriate for your horse's diet.

Finding The Balance

Carr says that in a healthy horse it's fairly difficult to oversupplement to a level that might throw off a horse's electrolyte balance. "There's an old saying that 'the dumbest kidney is smarter than the smartest doctor,' and that's because the kidneys can usually regulate and balance things regardless of what we give them," she says. However, there are some situations where supplementation issues can arise.

"We see problems when the horse's diet is deficient in some electrolytes, when the horse has existing renal (kidney) issues, or owners aren't providing free access to fresh water in addition to electrolyte water," says Carr. "Humans and horses aren't meant to drink electrolyte water exclusively, so when that’s their only water source they can ingest excessive amounts that the body might find difficult to excrete efficiently, especially if the kidneys are already compromised."

Horses that are sweating excessively or have diarrhea or other gastrointestinal disorders might also suffer electrolyte deficiencies. There are other factors in modern-day horse keeping that can contribute to electrolyte depletion, according to Kujawa. "During a half-hour trailer ride, a horse can have several bowel movements, especially new travelers or nervous horses. There's a significant electrolyte and water loss in manure, even if it's of normal consistency," she points out.

For a performance horse, add in the stress of transport and housing away from home, the physical and mental exertion from heavy competition, and extremes of heat and humidity, and it can be a recipe for electrolyte disaster--and that's in a healthy horse.

Electrolyte Cautions

While both Carr and Kujawa concur that the average healthy horse will ingest the majority of necessary electrolytes through his normal diet, there are some caveats and cautions to consider, especially if your horse has health issues:

  • If you're feeding a forage-only diet, sodium supplementation might be necessary (see "Water and Salt" sidebar).
  • Horses with renal disease or dysfunction might be unable to process additional supplements properly, but they're also likely to show signs of ill health and poor performance, meaning they won't be able to exert themselves enough to get into electrolyte trouble in the first place (when given a normal diet).
  • Horses with the metabolic disorder hyperkalemic periodic paralysis (HYPP) have a defect in their muscle membranes that can cause them to develop weakness and paresis (partial paralysis); controlling the potassium in their diet can help minimize episodes.
  • In situations where a horse has been salt-deprived for some time (e.g., in a neglect/rescue case), owners or managers should initially control access to salt. Because the horse is salt-starved, if given free-choice access he could overconsume sodium. This could cause the thirst response to go haywire, resulting in extreme thirst and the possibility of overwhelming or "drowning" the horse's kidneys with water consumption.

Electrolyte levels also can go awry when a horse is exhibiting diarrhea for any reason. When a horse has diarrhea, significant amounts of fluids and electrolytes are pulled from the body's own tissues and blood and are sent into the intestines, "coming out the hind end of the gastrointestinal (GI) tract," says Kujawa. "Simply put, it's due to an imbalance in the ion charges, with too many positives and not enough negatives, or vice versa, so the osmolarity (pertaining to osmosis) gets skewed."

During and following bouts of diarrhea, replenishing both electrolyte stores and hydration is critical to full recovery; Kujawa recommends supplying adequate fresh water at all times and using a top-dress electrolyte, following manufacturer's recommendations for "light work" supplementation.

Sport-Specific Supplementation

Depending on a horse's athletic endeavors, electrolyte supplementation practices vary widely. "In addition to the individual differences of each horse, there are different needs and preferences for delivery mechanism that vary by sport," reports Kujawa. "I think many endurance riders use paste, because their horses are walking 'metabolic tightropes,' and they need to know exactly how many grams of electrolytes they're consuming and exactly when it's given. Paste allows this control."

Racing is another high-intensity activity in which electrolyte supplementation might be closely monitored, but it involves a wrinkle not typical in other equine sports. "Horses that are given furosemide (Lasix, administered to lessen the severity of exercise-induced pulmonary hemmorhage) tend to urinate more, excreting electrolytes along the way," says Kujawa. "It's crucial to get those horses rehydrated following a race."

A horse that rarely goes off feed will do well with top-dress electrolytes on days of heavy exertion or sweating; however Kujawa says an average feed formulation with approximately 0.5% salt meets most animals' needs. She also emphasizes the importance of scrutinizing feed labels to ensure you offer an appropriate ration. "Commercial feeds are formulated to a specific quantity or weight in order to (provide) the correct amount of nutrients; horses given an amount other than the 'serving size' will be getting more or less nutrients accordingly."

Take-Home Message

When it comes to electrolytes, not every horse requires supplementation, although all horses need access to some form of salt to keep their thirst function and hydration balanced. As with any horse health decision, you should consider the animal's overall health, activity level, and environment to determine appropriate supplementation, and consult your veterinarian or an equine nutritionist whenever possible.

About the Author

Lisa Kemp

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