8/ APRIL 2024 THE RIDER Electrolyte Supplementation Horse sweat is considered hyper-


tonic, or isotonic, meaning that the con- centration of electrolytes in the sweat is higher than the concentration of elec- trolytes in the blood. This differs from humans, as the sweat that humans pro- duce is hypotonic. There is visual evi- dence of this when a horse sweats, as you will often be able to see the pres- ence of salt on their coat. If we compare sweat losses in horses and humans, ad- justed for surface area, the horse will sweat up to three times the amount of sweat as humans! The main electrolytes lost in equine


An Equine Nutrition Series by Madeline Boast,


MSc. Equine Nutrition Electrolytes supplements are com-


monly given to many horses, particu- larly in the summer months. When the temperature rises, the amount of sweat the horse produces increases. Addition- ally, in Ontario, our horses are often rid- den more frequently in the warmer weather.


What are electrolytes? Electrolytes are a class of minerals


that dissociate into electrically charged ions in water. They play a key role in the maintenance of fluid balance, osmotic pressure and are imperative to healthy nerve and muscle activity. For horses, sweating is the primary method of ther- moregulation during exercise. There- fore, when a horse is working, especially in a hotter climate, their electrolyte losses can be substantial.


sweat are sodium (Na+), chloride (Cl-), and potassium (K+). Magnesium (Mg2+) and calcium (Cl2+) are also lost; however, they are lost in smaller quantities. The need for electrolyte sup- plementation will depend on factors


such as the duration and intensity of ex- ercise, the heat and humidity they horse is working in, and if they are acclima- tized to that environment or not. For horses that are at maintenance,


their electrolyte requirements will gen- erally be met with a forage-based bal- anced diet and supplemental salt. However, when horses are in regular training, competition, or prolonged transport, it may warrant additional elec- trolyte supplementation. If you are un- sure if your horse requires additional electrolytes, you can always consult your veterinarian or nutritionist.


Why should they be supplemented? When a horse is exercising and


sweating, the sodium levels in their blood are normally lower than the pre- exercise levels. This can reduce their de- sire to drink water after exercise. Therefore, when a horse is given elec- trolytes after working it will increase the concentration of sodium in the blood and in turn, stimulate them to drink. Additionally, due to the high con- centrations of electrolytes lost in sweat,


their requirements increase when exer- cising. When choosing an electrolyte supplement for your horse it is important to use a product that mimics what the horse loses in their sweat and provide them with free choice access to fresh water.


What to look for in an electrolyte sup- plement? For my clients, I recommend being


cautious of the commercial electrolytes that provide large amounts of sugar (often dextrose). Of course, it is unnec- essary for sugar to be added to an elec- trolyte supplement as this is not something that is lost through the sweat. However, sugar is a popular addition to electrolytes as it increases the palatabil- ity of the product. If your horse is finicky, opting for a product that does contain dextrose is preferable as the product only does its job if they con- sume it! There were some prior claims that


sugar increased the uptake of elec- trolytes, but equine research has not sup- ported this claim. A 2013 study (Pagan et al. 2013) used thoroughbred horses and illustrated that an addition of dex- trose to the electrolyte supplement did not increase the rate of absorption or the retention of electrolytes. The inclusion of a minimal amount


of sugar can be valuable for palatability, however, when there are large amounts of sugar, the concentration of elec- trolytes is lower which in turn may re- sult in a less effective product. Therefore, when looking for a sup-


plement for your horse, it is recom- mended to choose a product that primarily supplies sodium, chloride, and potassium as those are the electrolytes lost in the highest concentrations, with lesser concentrations of magnesium and calcium. Encouraging Hydration We have all heard the saying “you


can lead a horse to water, but can’t make them drink”, however, we can encour- age it! The gold standard for electrolyte


supplementation is to train your horse to drink a water/electrolyte mixture 1-hour before exercise or transport. This is not always feasible, therefore, providing the electrolyte/water mixture afterwards to replenish losses is also an option. A word of caution with electrolyte


supplementation is that you must always ensure adequate water access. When you mix an electrolyte supplement with water, it is recommended to always pro- vide your horse with both the mixture as well as a bucket of plain fresh water. If your horse does not prefer the taste of the water mixture, it is crucial that they are not being discouraged of drinking. Additionally, if you are mixing the


electrolyte product with water it is rec- ommended to train your horse to drink it at home first, prior to using it at com- petition. Introducing something new, such as an electrolyte supplement mixed with their water, in a more stressful en- vironment will not set you up for suc- cess. Familiarizing your horse with the product and mixture prior to situations in which you need them to consume it is preferable. That way, you can ensure you are purchasing a product that they like, and are used to, prior to offering it for the first time before a competition or transport event. Think of it like how you practice loading your horse on the trailer, prior to the morning of the show!


Take Home Message Overall, if your horse is not in


work, simply providing them with a bal- anced forage-based diet, and supple- mental salt is adequate. However, for horses in regular training, competition, undergoing transportation, or even just sweating due to hot weather, you can add an electrolyte that matches the losses in sweat. The electrolyte will ide-


ally be mixed with water and provided to the horse, however, adding it to their feed is also an option, you just want to ensure they are not seriously dehydrated when this is done. To conclude, this article simply


scratches the surface of what ingredients to look for in an electrolyte supplement as well as guidance on how to provide them to your horse. If you have any spe- cific questions about how to optimally provide your horse with electrolytes, it is recommended to consult your nutri- tionist or veterinarian.


References: Waller, A. P., & Lindinger, M. I. (2021).


Pre-loading large volume oral elec- trolytes: tracing fluid and ion fluxes in horses during rest, exercise, and recov- ery. The Journal of Physiology, 599(16), 3879-3896. Pagan, J.D., B.M. Waldridge, J. Lange. 2013. Dextrose does not affect rate of absorption or retention of electrolytes in idle Thoroughbreds. Journal of Equine Veterinary Science. 33(5):349-350. (Proceedings of the 2013 Equine Sci- ence Society Symposium)


By: Madeline Boast, MSc. Equine Nu- trition About the author: Madeline


Boast completed her master’s in Equine Nutrition at the University of Guelph and started an independent nutrition company known as Balanced Bay. She has worked with a variety of equids – from miniature ponies to competing thoroughbreds. Through Balanced Bay she designs customized balanced nutri- tion plans that prioritize equine well- being. This includes diets for optimal performance as well as solving complex nutritional issues and everything in be- tween. For additional information see www.balancedbay.ca


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