Electrolyte Losses and Requirements

NAF explain when and how to replace those essential sweat losses for maximum recovery. Sweat losses are a critical aspect of equine nutrition, so it is beneficial to know how and when to use electrolytes. 

Sweat

Sweat is a clear, salty solution that horses – like us – use to help regulate body temperature. As the saying goes, horses sweat profusely, using it as their principle method of thermoregulation.

Sweat consists primarily of water and electrolytes. However, horse sweat also contains a protein, latherin, which causes the white foam seen with heavy sweating.

Electrolytes

Electrolytes are body salts, or ions, responsible for many functions within the body. The most important to the horse are Sodium, Potassium and Chloride, with Magnesium and Calcium playing smaller roles.

Once sweating starts, significant electrolytes levels may be lost in a relatively short amount of time. Many factors will influence how much they sweat, including temperature, humidity and exercise intensity.

Early signs of dehydration include a drop in performance and concentration, whilst long-term can lead to fatigue, weakness and has been associated with issues including thumps (Diaphragmatic flutter) and tying-up (Exertional rhabdomyolysis).

Signs of Dehydration

• Muscle weakness
• Increased heart rate
• Increased respiratory rate
• Increased rectal / core temperature
• Impaired mental function
• Muscle fasciculations (twitching)
• Loss of skin elasticity

How and When to Feed

Sweat losses need to be replaced whenever the horse has sweated. Generally whenever they are working above very light exercise. Horses are excellent at dissipating sweat, meaning it is easy for sweat losses to go relatively unnoticed; so what should we look for?

Measuring sweat losses can be tricky, but researchers have developed a ‘Sweat Score’ with easily recognisable signs. This shows that even a simple damp saddle cloth may relate to sweat losses of up to 4L in a typical Warmblood.

Sweat Score

(600kg Warmblood, fit for light to medium work)

Sweat Score	Signs	Sweat losses (L)
1	Under saddle partly dry, partly dark and moist. Sticky throat. Darker flanks.	1.6 - 4
2	Wet under saddle and on throat. Possible white areas at tack edges. Sweat obvious where reins touch, and inner hind legs.	4.0 – 7.2
3	Bridle leaves wet mark, often with foam. Saddle and throat areas wet. Flanks clearly wet.	7.2 – 9.3
4	Throat and flanks completely wet. Moist, dark wrinkles above the eyes. Possible white between inner hind legs from foaming.	9.6 – 11.8
5	Horses additionally dripping above the eyes and under belly.	12.7 - 18

(From Zeyner et al, 2014)

Whether hacking, schooling or competing, if you feel dampness under the saddle, or see signs around the throat and under the reins, then it is time to supplement electrolytes.

It is important to remember that as well as the electrolytes themselves the sweat losses include significant amounts of water. It is imperative that water is replaced alongside the electrolytes, as failure to do so can negatively impact uptake of both water and electrolytes across the gut wall.

Just because you feed electrolytes, does not mean they get into the horse.

Further, use of super-concentrated electrolytes, such as syringes, can act as an irritant in the stomach and cause gastric ulcers. The best way to avoid the risk is to add electrolytes to a really wet feed – something like well soaked sugar beet – or to acclimatise the horse to taking electrolytes from drinking water. A wet, fibrous feed is ideal, as the fibre also helps support the gut’s role as a fluid reservoir for hydration. Either way, ensure clean, fresh water is also always available.

Electrolytes should be given whenever the horse has worked, and when observed signs show that sweating has taken place. Remember, horses sweat when travelling, and research shows pre-loading is advised, i.e. feeding electrolytes one hour before travel. This should be sufficient to see them through the competition. However, for journeys longer than two hours long, rest breaks should be provided and electrolytes fed. Post-competition electrolyte supplementation is also important to aid recovery.

As horse owners, it is our responsibility to know the importance of electrolytes to working horses at all levels.

Know when and how to replace those essential elements with safe and appropriate supplementation.