Kate Hore RNutr (Animal) Senior Nutritionist at NAF

Now summer is here, one of the most important aspects of your horse’s summer health is to ensure he stays suitably hydrated, and what is lost through sweat is adequately replaced.

Water is, quite simply, the most important aspect of your horses’ diet. Essential to life, water makes up around 65 - 75% of the horse’s bodyweight. A lack of water is seen initially as reduced appetite and poor performance; but can lead to depression, bone and cartilage damage and, ultimately, be fatal to the animal if not rehydrated. Water is essential not only to hydration itself, but all aspects of general health. Research now also links a lack of fresh water directly to an increase in gastric ulcers; so for all these reasons it’s vital that your horse always has clean, fresh water available in both the field and stable. 

As water is lost through sweat it is essential that we replace it, but not just the water but also the essential body salts, or electrolytes, that are lost alongside.

Of the essential body salts sodium chloride, or basic salt, is key and should be supplemented daily year round. Having a salt lick available in the stable and field allows your horse to take what he needs, but beware that flavoured licks can sometimes be eaten like sweets! Once exercise is increased, and as the weather warms up, you should upgrade basic salt to electrolytes which provide all essential body salts, ie. sodium, calcium, potassium, magnesium and chloride. Failure to replace these body salts can affect the thirst mechanism by failure to replace lost water, thus leaving the horse dehydrated. Ensure you always feed electrolytes with clean, fresh water, as studies have recorded losses of up to 60 litres (110 pints) of sweat per day in competition*.

It’s worth noting that electrolytes must be fed in a way that works with the body, or more damage can be done. For example using a very concentrated form of electrolytes (i.e. a paste) can actually draw water out of the gut as it passes through, hence leaving the horse more dehydrated than he was before, and has been identified as a risk factor for gastric ulcers. For competing horses look for electrolytes which can be easily dissolved in a bucket of water, but we all know the adage ‘you can take a horse to water but you can’t make them drink’, so for those types fed in a nice wet feed is a tasty way to ensure the horse is also rehydrating at the same time.

Don’t forget yourself – if you’re riding all day at a show, maybe try an isotonic sports drink to replace lost electrolytes, rather than reaching for the fizzy drinks.

In conclusion, whether competing or just enjoying a summer hack, ensure you pay attention to your and your horse’s electrolyte and water requirements to stay alert and focused.


* Top level endurance competition in humid climates have recorded these levels.