Electrolytes are such a heavily used product for both humans and horses, yet the details of what, when, and why to provide them can get lost in blanket assumptions. For humans, if we plan to spend time outdoors doing, literally anything, in hot and/or humid weather, grabbing a bottle of Gatorade or Propel is common practice. The blanket assumption is that if we’re going to get hot or sweaty, our bodies need more than just water to replenish and keep hydrated. We apply the same assumption to our horses. While this line of thinking is not wrong, it’s important to remember that there are more things to consider when using electrolytes.
What are electrolytes, exactly? Electrolytes are a combination of minerals sold as a commercial product, usually as a salt or paste. The combination typically contains sodium, potassium, magnesium, calcium, chloride, bicarbonate and fractional amounts of other trace minerals. When dissolved in water, electrolytes separate into charged ions, creating an electrical-chemical current that acts as the catalyst for many functions within the horse’s bodily processes, including muscle contraction, nutrient absorption, nerve firing, acid-base balance, and fluid regulation. Electrolytes function like triage nurses, directing the water that a horse ingests to the cells, organs, and areas that need it most.
Many options on the market also contain glucose or sugar in their formulation. It’s important to note that horses differ from humans regarding electrolyte supplementation. For horses, sugar is not an important component. While it can improve the palatability of the electrolyte, it is not necessary. For those horses dealing with metabolic or insulin regulation issues, ensuring that the electrolyte you offer DOES NOT contain sugar is vitally important. The most significant 
elements of electrolytes are sodium (salt) and potassium. These minerals are generally consumed in sufficient amounts for the average horse at maintenance through their commercial feed and forage. However, as we will discuss further, there are many circumstances in which electrolyte supplementation is necessary.
If the average horse at maintenance consumes enough salt and potassium through their feed and forage, why would they need an electrolyte supplement?
Let’s start with the mechanics of the sweating process:
1) The metabolic process that generates body heat begins when fat and glycogen are broken down and used as energy
2) The blood just under the skin warms and the excess heat rolls off the body and dissipates into the air
3) If the body continues to increase in temperature the next stage relies on the electrolytes within the body to activate the sweat glands
4) As sweat comes out of the horse’s pores and evaporates it creates a natural cooling system to help the body lower the internal temperature
Sweat consists of both water and lots of electrolytes. So, when horses sweat, they lose not only water but also the valuable minerals responsible for many biochemical functions within the body. Consequently, replenishment is crucial to the horse’s health. The more a horse sweats, the quicker it may need replenishment. For example, the average horse that sweats minimally due to environmental temperature or exercise is likely getting enough salt/potassium replenishment through the feed and forage it consumes. It may still be prudent to make both a white salt and trace mineral salt free-choice accessible via a loose salt/mineral tub or blocks. On the other hand, a horse actively training or in extremely hot environments and sweating profusely could benefit from additional electrolyte supplementation via a granular top-dress or paste.
Electrolyte imbalances and deficiencies cause dehydration and can affect the horse in multiple ways, from energy loss, weak or trembling muscles, to instability and in severe cases, can even cause death. Therefore, it is important to discern when electrolyte supplementation is necessary and when it could be dangerous.
When Electrolyte Supplementation Can Be HELPFUL
For Any Reason or Combination of Reasons That Cause Excessive Sweating:
- Strenuous or prolonged exercise
- Hot and/or humid temperatures
- Illness
- Dehydration
- Diarrhea
- Fever
- Metabolic conditions such as Cushing's when the horse retains too much haircoat which, in turn, creates more heat and causes perspiration
- Traveling/Transportation
- Stressful Situations
- Showing
- Any events outside of the normal everyday routine
- When the Weather is Cold or Experiencing Variable Conditions – Cold temperatures and fluctuating weather can deter some horses from drinking enough water. Adding an electrolyte supplement can help encourage them to drink more.
- When Recommended by the Veterinarian or Nutritionist
When Electrolyte Supplementation Can Be HARMFUL
- Administering at the Wrong Time or the Wrong Dosage. Electrolytes are not stored in the body; they pass through the system and, if not utilized, the kidneys filter them out, and they are excreted in the urine. Consequently, ‘pre-loading’ a horse with electrolytes before a workout or event can cause an electrolyte imbalance. Similarly, administering a higher dosage than recommended by the manufacturer can also create electrolyte imbalances. These imbalances can trigger numerous other health-related issues.
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If the Horse Has Not Had Access to Water and/or is Already Dehydrated.
When administering electrolytes, it is important first to ensure the horse has access to fresh, clean water. Giving electrolytes without access to water can cause electrolyte imbalances. Ensure the horse has actively consumed water before administration. Remember, electrolytes encourage the horse to drink more because the saltiness makes them thirsty. For the horse to improve its hydration, it must drink more. Electrolytes alone do not increase hydration.
- Underlying Health Conditions. If you are dealing with any kind of health concerns, especially horses with kidney or renal dysfunction, heart or metabolic disorders, consult with your veterinarian before beginning electrolyte supplementation. They can help direct you to the right product and dosage specific to your horse’s needs.
Electrolyte Forms
- Paste – For immediate and forced consumption
- Powder/Salt – To use as a top-dress in either feed or water
- If adding electrolytes to water, make sure to offer a bucket with the supplement and a bucket or tank without the supplement. The goal is to increase hydration. If the horse is picky, it can be deterred from drinking enough or any at all if it does not like the smell or taste of the water with the supplement.
- If adding to feed, be sure to keep a close eye on the feed bucket after the horse has consumed its meal. Again, if the horse is sensitive and does not like the smell or taste of the supplement, it can cause them to eat less or walk away from their feed tub altogether. Some horses can rifle through their feed with the quiver of their muzzles to sift and separate the powder or salts to the bottom of the tub. If you find that the feed is gone, but the powder or salts remain, you may want to consider a different top-dress electrolyte product that may be more appealing to them or consider using a paste.
- Free Choice Salt and Mineral – Having free-choice salt and mineral available to your horse is a wonderful idea, especially if your horse is simply turned out and living his/her best life. Keep in mind, though, for a horse that is actively working or dealing with events, illness or out-of-the-normal conditions, self-serve supplementation is likely not enough. On the flip side of this, be sure to monitor the consumption rate of free choice options. Some horses get bored or like the taste and will mow through free choice salts and minerals like candy. Too much of a good thing can be a bad thing, too. Free Choice options include:
- White Salt AND/OR Trace Mineral Salt
- 4lb Brick
- 50lb Block
- Loose Salt/Mineral
The tips in this article can help you avoid blanket electrolyte assumptions to help you maximize your management efforts. Electrolyte supplementation can be a useful tool when it comes to keeping horses well-hydrated. Understanding the role electrolytes play and how and when to best utilize them are critical components for proper management. If you have questions or would like to talk to one of our Equine Specialists about choosing the right electrolyte product for your horse, give us a call at The Mill. We have a wide variety of options and are always happy to help.
