Did you know a horse not in work loses up to 10 litres a day in sweat! That means losses of 10 grams of Sodium, 10 grams of Chloride, 25 grams of Potassium and 10 grams of Magnesium!

A horse in mid-range work sweats by comparison 27-43 litres a day.  That means losses of up to 43 grams of Sodium, 71 grams of Chloride, 43 grams of Potassium and 13 grams of Magnesium.

Signs of electrolyte deficiency & heat stoke include:

  •              Fatigue
  •              Exhaustion
  •              Impaction colic – constipation
  •              Dull coat
  •              Slowed rates of chewing
  •              Uncoordinated chewing
  •              Sunken eyes
  •              Weight loss
  •              Unsteady gait
  •              Depression
  •              Muscle contractions
  •              Listlessness
  •              Poor performance
  •              Dark urine
  •              Decreased water uptake
  •              Tying up
  •              Diaphragmatic flutter
Electrolyte Model

The horse’s body cannot retain water without the presence of electrolytes.  Adding electrolytes to the horses feed helps replenish the lost fluid.  However, after prolonged sweating it will take several days of electrolyte supplementation to completely replenish losses.  Hence supply of necessary electrolytes should continue. 

Critical attention needs to be adhered to on how to sustain and replace electrolytes.  Sadly, some recommend loading hard feed with salt.  Is this safe or even necessary?

Studies consistently demonstrate sodium chloride (salt) should be available for the horse ad lib in the paddock/stables all year round in the forms of either plain iodized, cobalt-iodized or trace-mineralized salt (Himalayan Rock – often the easiest choice). 

In Nutrient Requirements of Horses, the National Research Council Research indicates a horse will naturally uptake only 0 to 62mg/kg BW/day.  (Example: a 500kg horse would uptake naturally between 0 gr a day to a maximum of 31 gr by free choice).  Common sense dictates adding more than 31 gr a day to hard feed (including what is already available in their feeds/supplements) would be unnecessary and even dangerous in consideration of Holbrook et.al., 2005 ‘repeated oral administration of an electrolyte solution has been associated with an exacerbation of gastric ulcers.’ *Jansson and Dahlborn (1999)

(Read more at http://www.horseandhound.co.uk/features/understanding-essential-electrolytes-450961#kTLIf4fixqlVCAAC.99

“When left on their own, horses have the innate ability to regulate sodium chloride equilibrium within their bodies. Therefore, all horses should be offered ad libitum salt.”


So how do you replace these significant electrolyte losses safely?  A portion of sodium and chloride can be obtained by providing a Himalayan salt rock.  Potassium can be picked up in forage, typically hay provides 10-20 grams per kg.  German research revealed horses fed adequate forage maintained better water and potassium balances during exercise than horses fed a high concentrate diet (grain).

Magnesium however is not readily available in sufficient quantities to replenish a horse’s needs.  Magnesium must be fed in conjunction with Calcium (close to 3:1 Calcium: Magnesium) in conjunction with Boron to be adequately supplied to and utilised by the small intestine.

The other time to consider the use electrolytes is during wintry weather, especially during Autumn and Winter.  When horses tend to drink less. Horses prefer water that is 7-18OC and they will drink less if it is too hot or cold. The water content of pasture is about 80% compared to the water content of hay which is only about 10%. The danger that can occur with wintry weather and hay-only diets is that horses can become dehydrated and the risk of impaction colic is increased. By feeding electrolytes daily during the cooler months the risk of impaction colic can be reduced.

Too much salt?

Signs of salt toxicity are frequent urination, weakness, colic, diarrhea, irregular heartbeat, muscle tremors, abdominal pain and central nervous system manifestations, such as circling, blindness, seizures, and partial paralysis.

Overuse of electrolytes might cause physical injury, namely ulcers, to mouth and stomach tissues. In addition to following manufacturer recommendations, other management strategies to avoid ulcers when supplementing electrolytes include never administering electrolytes on an empty stomach, mixing electrolytes with some type of stomach buffer, feeding alfalfa, and rinsing the mouth with water if dosing electrolytes with a syringe.

Although horses may develop salt toxicosis or hypernatremia (excessive sodium in the blood), the condition is rare. Toxicosis is usually the result of overconsumption of salt water when alternative water sources are unavailable; overfeeding salt to salt-deficient horses; or offering a ration with 2% or more salt with inadequate water supply.


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