Electrolytes and Competition Hydration

, Electrolytes and Competition Hydration
By November 16, 2018 No Comments

What are electrolytes and why are they important?

Electrolytes are body salts that are key for fluid balance but are lost in sweat. Electrolytes are essential nutrients that are involved in a number of body processes but are of utmost importance for healthy fluid balance and post-exercise recovery. Owners need to understand how to feed electrolytes correctly in order to maintain optimal health and performance in their horses. Working horses specifically need to have these body salts replaced daily in order to stay healthy and well hydrated.

 Electrolytes and hydration

The horse’s body consists of about 61-72% fluid, which exists in two forms: in the cells and between them. The electrolyte salts ensure the fluid remains at the correct concentration and are involved in movements of different compounds in and out of the cells. The main electrolytes are sodium, chloride, potassium, magnesium and calcium.

 Water is involved in all body processes and is essential for normal body function. Water balance is the maintenance of equality between water input and output. Input occurs through drinking, eating and metabolic processes, whereas output occurs through faeces, urine, respiration and sweating (cutaneous). This process is dynamic i.e. changing all the time.

 Horses can lose 10-12 litres of sweat per hour during exercise in hot and humid weather. Horse sweat is loaded with electrolytes, at around 9g total per litre. A loss of 25 litres of sweat can be associated with losses of 175 g of sodium and 55 g of chloride. This equates to losses of 20% of sodium and 27% of chloride from body fluid compartments. For optimal health and performance, these lost electrolytes and body water must be replenished.

 The ideal electrolyte should be a mixture of the body salts lost in sweat, which dissolves well in water and has flavours added to boost palatability. It should be fed every day to working horses.

 Thirst response

Because horses lose a lot of electrolytes when sweating, they can sometimes lose their thirst response. Their body water and electrolyte loss is such that the body does not recognise the need to drink. In this case, getting electrolytes into the horse is imperative to get them drinking.

 Signs of electrolyte deficiency

Most horse diets are deficient in sodium without extra electrolytes supplementation. Signs of electrolyte deficiency include:

  • Poor performance
  • Lethargy
  • Slow recovery after exercise
  • Muscle problems including an increased risk of tying up
  • Thumps (Synchronous diaphragmatic flutter)
  • Decreased sweating and associated risk of hyperthermia (overheating)

 Did you know?

  • Just 2% dehydration could limit exercise performance, 8-10% will cause ill health and over 15%, death
  • Transportation causes dehydration, so extra care should be taken for horses travelling to competitions
  • Working horses may not take in enough salt from a block
  • Fresh, growing pasture grass can be about 80% water and horses grazing it may not drink at all
  • Some stabled horses dunk their hay in their water buckets, to make it more like their natural forage
  • Feed-deprived horses tend to drink more water

Why might an oral hydration solution be required?

The higher the sweat rates, the greater the need for supplementary electrolytes, especially sodium. Feeding them daily ensures your horse starts their competition and travel to venues fully hydrated. The most effective way to replace fluid losses after exercise is to have the horse drink an electrolyte solution, ideally an isotonic one – an ‘oral rehydration solution (ORS)’. Horses given ORS post-exercise have better muscle glycogen replenishment rates than those who are not, so they may well aid post-exercise recovery.

 Fresh water without electrolytes will not effectively rehydrate horses post-exercise because it can suppress their desire to drink. Working horses should be trained to drink oral rehydration solutions, which you can make by adding 45g salts in 5 litres of water. Without enough electrolytes in the diet (both in the feed and in solution), the body cannot hold onto water.

How to feed electrolytes correctly

Electrolytes are fed in two different ways:

  • In the feed to replenish salts lost in sweat
  • In water as a way to enhance rehydration in a dehydrated horse, post-exercise

 ELECTROLYTE REPLENISHMENT: Add electrolytes into bucket feed daily to working horses, adjusting the amount according to the size of horse or pony, level of work and amount of sweat loss. Feed around 19-80g (1–4 tablespoons) of salts daily, according to sweat rates and how much the horse will eat.

 REHYDRATION: Mix 45 g of electrolytes in 5 litres of water. Ideally train the horse to drink the mixture by offering it during training, straight after work. Salt does not taste so salty when the body is low in sodium, so offering an oral rehydration solution after exercise can help uptake.

 Equestrizone Everyday Electrolytes contain just the right mixture of different types of body salts to replenish those lost in sweat and dissolve well in water. The product also contains palatable herbal flavours, helping to ensure that horses with high requirements will eat all the salt they need.



  • Geor et al (2013) Equine Applied and Clinical Nutrition. Saunders Elsevier, Edinburgh.
  • MacLeod (2007) The Truth About Feeding Your Horse. JA Allen, London
  • NRC (2007) Nutrient Requirements of Horses. 6th ed. The National Academies Press, Washington DC. 
  • Lindinger, M.I. & Ecker, G. L. (2013) Gastric emptying, intestinal absorption of electrolytes and exercise performance in electrolyte-supplemented horses. Experimental Physiology, 98 (1), 193-206.


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