JULY/AUGUST 2024 THE RIDER /21 Preventing Dehydration in the Horse


Guelph, ON June 18, 2024 - With exercise, the body temper- ature rises. This heat must be dissipated, or the horse will lit- erally “cook”! The body cools itself through the evaporation of sweat, so sweating is espe- cially important for the exercis- ing horse. The sweat contains water and electrolytes, or salts. The main electrolytes are sodium, chloride, potassium, calcium, and magnesium. When the body loses water and electrolytes, various functions are compromised, and the health of the horse can be at risk. To ensure that your horse remains healthy, learn to effec- tively replace both the water and electrolytes – and the elec- trolytes must be replaced in bal- ance with what has been lost (While this article focuses on exercising horses, it is impor- tant to realize that heat stress from confinement in the horse trailer for hours can result in profuse sweat losses due to hy- perthermia and anxiety).


Replacing the Losses For sedentary horses or


horses undergoing low level, or short-term work, salt losses through sweat can generally be readily replenished by a good quality diet and provision of loose salt in a bucket or added to the feed if necessary. How- ever, horses in training (and therefore sweating) several days a week, and regularly in- volved in intense or prolonged activity during competition, may become chronically defi- cient in electrolytes, because there may not be enough in the feed to replace those losses. Horses involved in long-term, higher-intensity work may lose electrolytes at a rapid rate (10 to 15 L of sweat per hour) and the sudden decrease in elec- trolytes can cause muscle prob- lems and heat stress injuries.


How Do You Help Your Horse? When you help your horse


minimize the losses or quickly replace water and electrolyte losses, then you will be helping your horse maintain optimal health and optimal perform- ance. Remember that you can always slow down! Fast speed is the best way to lose lots of water and electrolytes and risk heat stress in your horse. Learn- ing to effectively cool out your horse at rest stops is also para- mount to prevent heat stress and lower sweat losses. Before you start through


all the electrolyte information though, make sure that you have your horse on a proper op- timal diet. Then make sure that you have trained your horse to the level needed for the event and the terrain. Training must incorporate a strategy for elec- trolyte supplementation before, possibly during and after exer- cise / transport. You cannot


make up for poor preparation with extra electrolytes! The ways in which


chronic and acute losses of electrolytes and fluids may be minimized or eliminated are presented briefly here. 1. During the week, make sure the horse has a high-quality diet and add electrolytes to wetted feeds only if the horse has been working at intensities and dura- tions causing moderate to high sweat losses. Lower losses are easily replenished by normal amounts of electrolytes in the feed and good quality hay. Al- ways make sure that the horse has access to a clean salt block. It may be advisable to break the block up into smaller pieces and place these in the grain bin during the summer to increase salt intake. For many horses, the salt block will not give them enough salt. For these horses, place a small container fixed to the wall in the stall to hold free- running salt. Make sure fresh water is always available. 2. One to two hours before the event (or before a long trailer ride), it may be beneficial to give the horse an oral dose of electrolytes to build up a reser- voir in the gut – but adequate amounts of water must be pro- vided with oral electrolyte ad- ministration. Do not give electrolytes to a horse that is al- ready dehydrated. A high con- centration in the gut may actually pull water from the blood, increasing the dehydra- tion of the body. Attempt to give at least one gallon of water before or immediately after the dose, or give the dose in the water if the horse will drink it. Feeding wet hay and/or soaked beet pulp four to five hours be- fore the event may also in- crease the water in the gut which would be available to the horse when dehydration devel- ops. 3. Do use electrolyte prepara- tions with glucose (dextrose) as this promotes sodium and water absorption in the gut. However, high-sugar supplements can cause a surge of glucose (blood glucose) in the bloodstream which in turn causes a release of insulin. The insulin causes an uptake of glucose from the blood and could cause the horse to become hypoglycemic while it is exercising (“sugar crash”). Also, avoid high-fat supple- ments as this may slow down the absorption of electrolytes in the gut. Fat supplements are beneficial during training as part of the diet but should not be used during rest breaks. 4. Supplement water and elec- trolytes 1-2 hours before as well as early in an endurance ride or when you know the horse will be needing elec- trolytes. You may increase the blood sodium level and the horse may start drinking sooner as a result. If the weather is hot, don’t wait until the horse shows


signs of dehydration before ad- ministering electrolytes. If you wait until the horse “looks” like it needs electrolytes, it will have some level of dehydration by that time and less blood is available to the gut for normal function. Also, if an electrolyte mix is given without an ade- quate amount of water, the high concentration of ions may actu- ally pull water into the gut, and this takes more water out of the blood, further dehydrating the horse. 5. For endurance horses, do not use an electrolyte supplement containing bicarbonate. Gener- ally, due to the sweat loss, the horse is already alkalotic, and the bicarbonate would increase this. 6. Once the event is over, do not stop giving water with bal- anced electrolytes. The horse may still be sweating for some time after the event to reduce body temperature. It may be more important to get the elec- trolytes into the horse after the event, and before the horse starts eating dry feeds and hay If a horse consumes water only, this will actually “dilute” the blood, causing urination, fur- thering water and electrolyte losses through the kidneys and lowering the blood electrolyte concentrations. If the horse is already dehydrated and low in potassium due to sweat losses, then this condition can be wors- ened by feeding the horse large amounts of dry hay. The hay re-


quires a lot of water for diges- tive enzymes and will pull water and potassium into the gut, worsening the effects of dehydration. Allow the horse to drink water with electrolytes until satisfied before providing hay and feed, i.e. replace fluids and electrolytes first, then pro- vide the feed, when possible. 7. Ensure that you are helping the horse to cool itself. The blood flow is shunted away from the gut to the muscles and skin when the horse is over- heated in order to assist with heat loss through sweating. Learn to monitor the rectal tem- perature of the horse and ob- serve the vasodilation of the skin to ensure the horse is cool- ing out. Once the horse is cooled out, there will be more blood available to establish nor- mal blood flow to the gut. The intake of electrolytes assists in the restoration of cell and plasma volume, and this aids in cooling and reduces work of the heart by keeping blood vol- ume high. Using cool and cold water has been shown to safely and effectively cool hot/warm horses. 8. Ask your veterinarian to teach you to perform skin pinch, capillary and jugular re- fill and mucous membrane test- ing as well as listening for gut sounds. Monitor the clinical pa- rameters yourself to help deter- mine if electrolyte solutions are necessary. These will help you to determine if the horse needs


more electrolytes and fluid. If these parameters are not show- ing an improvement about half an hour after the horse has had fluid and electrolytes, then a second dose of electrolytes may be necessary as long as the horse has had a good drink of water. If the horse is not drink- ing, consult the ride veterinar- ian. They may help you administer small amounts of electrolytes frequently to help encourage the horse to start drinking. 9. Encourage higher fluid in- take by making up a “slush” or sloppy mash of the feed mixed in with lots of water, and per- haps pieces of apples and car- rots. You may want


to


experiment with different flavours such as apple or or- ange to see if the horse likes it. 10. Frequent small doses of supplements are preferable to one or two large doses. Ensure the horse has access to water and possibly some electrolytes at least every two hours. The electrolyte powder can be mixed up with water and some apple sauce and squirted into the horse’s mouth (open the side of the lip and squirt it to the back of the mouth with the head held up) using a 60 cc sy- ringe with the nib cut off. Tip: 35mm film canisters make an easy way of measuring and car- rying electrolytes as they hold one ounce or approximately 30 grams. Or mix the electrolytes into a sloppy mash which you are using to feed the horse. If a slurry or mash high in elec- trolytes is used, ensure that as much water is consumed as possible with the slurry and al- ways have water available. 11. If your horse refuses to drink even though you have given it lots of time, you might try putting a tablespoon of salt onto the tongue or into the lip of the horse. The salty taste sometimes causes the horse to start drinking. You will want to consult with the ride veterinar-


ian to make sure that your horse is okay and not at risk of a health problem. Ideally, you want to train your horse to drink water with a balanced electrolyte supplement as part of your training strategy. If you are new to events which might require supplementation of electrolytes, discuss the needs with a knowledgeable veteri- narian and with other riders who have been competing suc- cessfully. Their routines will not be exactly what your horse needs, but it gives you a place to start and, by trial and error, you will learn to adjust the dosages to suit the needs of your horse. You may also be inter-


ested in reading about how heat and humidity affect the horses’ ability to perform.


Equine Thermoregulation In- fographic: https://bit.ly/EquineTher- moregulation


Dehydration check Videos: Capillary


Refill:


ht tps : / /youtu.be /qQwk- NEOnxlQ


Skin Pinch test: https://youtu.be/5TdFx_dg75I


About Equine Guelph: Equine Guelph is the


horse owners’ and care givers’ Centre at the University of Guelph in Canada. It is a unique partnership dedicated to the health and well-being of horses, supported and overseen by equine industry groups. Equine Guelph is the epicentre for academia, industry and gov- ernment - for the good of the equine industry as a whole. For further


information, visit www.equineguelph.ca.


Story by: Dr. Mike Lindinger & Gayle Ecker


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