Exercising in hot weather and other considerations to support optimal performance

17th July 2020

Water and electrolyte loss during work and the importance of rehydration and replenishment afterwards

If horses are not working and the weather is cold, they will require lower amounts of electrolytes (salts) to maintain essential bodily processes. A 500 Kg horse will require 10g sodium, 25g potassium, 40g chloride, to replenish daily losses. These baseline levels will often be satisfied through normal daily consumption of forages (grasses and hays that the horse eats). Once a horse enters work, these requirements will start to increase, at which point as owners we should consider supplementation and/or the use of a feed with added electrolytes.

Exercise produces heat energy, which is lost through evaporation. Most of this evaporation occurs through the skin and through breathing. When the temperature outside increases, respiratory losses decrease and sweating increases. The body water lost in sweat can be significant (around 15 litres for normal canter work in summer conditions in the UK), as can the added electrolyte losses. Horses sweat contains 2.8g sodium, 1g potassium, 5.3g chloride and 0.12g calcium and 0.05g magnesium per litre. A good estimate of losses during work is between 4-10 litres an hour, however, as previously mentioned, temperature, as well as intensity of exercise, fitness, length of coat and humidity can all influence losses. (Hoyt et. al.1995)

If a horse is low on electrolytes, or not in isotonic balance, that they will be unable to perform at their best. Research has demonstrated that excessive exercise without providing electrolyte replacement afterwards will lead to a 1-4% drop in performance. A study performed at the Animal Health Trust in Newmarket found that in 144 horses that repeatedly tied-up, 100 of them had poor electrolyte balance. It is therefore important to seek out a supplement that will provide balanced electrolyte replenishment after work, in addition to ensuring the horse always has free access to water. (Frape et. al. 2008)

Electrolytes are also cited as an important part of muscle recovery after work. This is because sodium and potassium are involved in muscle contraction at a cellular level. If either is out of balance or low, skeletal muscles used during work will not contract at their optimum, possibly leading to weakness and/or poor performance.  (Hoyt et. al. 1998)

The role of the hindgut

Horses can maintain a reservoir of water and electrolytes in their hindgut if their diet contains soluble fibres and their hindgut pH remains in its optimal range. Every 1g of fibre consumed allows the hindgut to hold 5ml of water (and associated electrolytes). This can help a horse in heavy work, as this hindgut reservoir can help support recovery immediately post exercise by rapidly replacing lost salts. (Hoyt et. al. 1995).

Antioxidants and recovery from work

Optimising recovery is essential if you’re trying to gain a leading edge and support performance. When horses exercise oxidative stress increases throughout the bodily systems. Antioxidants like Vitamin E have been shown to mop up the free radicals released from oxidative stress, therefore lessening the impact of exercise on the body. The entire D&H Performance Range has elevated vitamin E levels, to help horses achieve and recover more completely. D&H’s unique QLC antioxidant package that is included in several Performance Range products as well, including Elite Sport Muesli, Performance Concentrate Muesli, and Ultimate Balancer, helps improve total antioxidant capacity in the body and the ongoing bioavailability of vitamin E in the blood stream. Together, Vitamin E and QLC can help improve recovery time and extent. (Lowe et. al. 1992)


When reviewing your feeding and exercise plan with optimal recovery and performance in mind, it is essential that you feed for your horse’s individual requirements (i.e. workload, clinical conditions, temperament). Workload duration and intensity can heavily influence calorie and energy types needed, much like our own added needs when heavily exercising. If you have questions about the specific products you are using, consider discussing them with our Nutritional Helpline. They will be able to offer advice and support with your review.

Once your feeding plan is set, monitoring your horse’s “normal” can be an incredibly beneficial way to cross check progress. To assess hydration, start by monitoring their normal water intake in various conditions (at home when at rest, in work, in various environmental temperatures, and whilst away at competitions). Recording normal behaviour can help you identify potential risk areas. For example, if you discover that your horse drinks much less whilst away at competitions, despite the same workload. Other parameters that can be assessed to check hydration status include body weight before and after work, mucous membrane wetness, and associated capillary refill time. Speak with your vet at their next yard visit to learn how to check these parameters. Vets will also assess the hydration levels by listening to your horse’s heart and by taking a blood sample to look at the concentration of red blood cells (PCV), and at competition gates or rest points, they are usually assessing heart rate, respiratory rate, mucous membrane colour, capillary refill time, body temperature, gut motility, and soundness/movement. With a bit of practice, these parameters can also be assessed at home, in addition to the other more general, but equally important parameters like water intake, body weight, and body condition.

In summary, exercising in hot weather can increase requirements of the horse quite significantly. Electrolytes and water stores will be two parameters most effected. There are several ingredients that can help support recovery from work in hot weather. Once your nutrition plan is set, monitoring can help you identify early warning signs that something might not be quite right. If you have any questions about your current plan, about riding in hot weather, or about feeding to support optimal performance, please consider reaching out to our Nutritional Helpline available via livechat on our website, by email, via phone on 01270 782 223.


Williamson, H. M. (1974). Normal and abnormal electrolyte levels in the racing horse and their effect on performance. Journal of the South African Veterinary Association, 45(4), 335340.

Frape, D. (2008). Equine nutrition and feeding.

NRC 6TH Edition, pages 69-108

Hoyt et al 1995

Holbrook et al 2005

Meyer 1992

Equine nutrition, Saunders Elsevier

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