SPILLERS – Feeding the competition horse in hot weather

With the heatwave set to continue, we thought it timely to bring you our top tips on hot weather feeding. Whether you heading out for your first BE8O or competing at CCI 4*, soaring temperatures can present a number of challenges.

Copyright by Arnd Bronkhorst ©


Although not a nutrient, water is the most important component of the horse’s diet. In fact, water accounts for approximately 65% of the horse’s body mass and is involved in almost every physiological process in the body. Dehydration may lead to tying up, respiratory stress, colic, poor performance, heat stroke and exhaustion.

  • Some horses are reluctant to drink ‘strange’ water so where possible, taking water with you to events may help. Alternatively, the addition of apple juice may help to mask differences in taste but make sure you ‘teach’ your horse to drink flavoured solutions at home first.
  • Do not withhold water prior to exercise.
  • Allowing horses to drink immediately after exercise will not cause colic but withholding water may delay rehydration. Offer small amounts of water in the first 30 minutes and free access once the horse has cooled down fully.

Fibre & hydration

Depending on the diet, water in the digestive system accounts for approximately 19-21% of the horse’s bodyweight. Importantly, the ‘reservoir’ of fluid in the large intestine or ‘hindgut’ is thought to provide a source of water and electrolytes that can be drawn upon during exercise. Research has shown that the amount and type of fibre in the horse’s diet may affect the size of this reservoir, with horses on high forage diets having been seen to be less dehydrated following a standard exercise test than horses on low forage diets.

Did you know? Whilst 10-15% dehydration can be fatal, it is estimated that just 2% dehydration can affect performance. 

Signs of Dehydration

  • Loss of skin elasticity – do the pinch test!
  • Slow capillary refill – press gently on the horse’s gum (upper jaw)
  • Dry gums
  • Dry, red eyes
  • Thick, sticky saliva
  • Increased pulse and respiration rate
  • Depression 
  • Lethargy


When horses sweat they lose electrolytes, the main ones being sodium, potassium and chloride.

Electrolytes (mineral salts) play an important role in many cell functions, including muscle contractions and the transmission of nerve impulses. A lack or imbalance of electrolytes can affect almost every physiological process in the horse’s body and may lead to conditions such as heat stress, fatigue, synchronous diaphragmatic flutter (thumps) and tying-up.

  • Electrolyte losses are directly related to sweat loss which for horses exercising in extreme conditions, can be as high 10-15 litres per hour! 
  • Although it’s not possible to ‘pre-load’ with electrolytes, imbalances prior to exercise should be avoided.
  • Unless they are sweating heavily, free access to a salt lick is sufficient for horses in light work.
  • Table salt (the salt you put on your chips!) and plenty of forage is an effective replacement for the majority of horses in medium and hard work. Table salt is a combination of sodium and chloride whilst forage is naturally high in potassium.
  • If adding electrolytes to water, always provide plain water as an alternative.
  • Take care if using pastes and syringes, particularly during exercise. If the horse does not drink sufficiently, high concentrations of salt will result in water from the body being drawn to the digestive system which may lead to further dehydration. For the same reason, make sure your horse has started drinking before adding electrolytes to his feed.
  • Avoid using electrolytes pastes for horses prone to gastric ulcers. A study in endurance horses (Holbrook et al 2005) found a significant increase in the number and severity of ulcers in horses given electrolytes by syringe compared to those given a placebo.

Lazy in the heat?

We all know that exercising in hot weather can be hard work and it’s not uncommon for horses to become lethargic as the temperature rises. 

  • Although cereal based feeds can help to achieve a more energetic response in some horses, high starch diets are not suitable for horse prone to clinical conditions such as gastric ulcers and tying up.
  • Resist the temptation to introduce a new immediately before a competition. Sudden changes in diet upset the microbial population of the gut and may lead to colic or tying up. 
  • Whilst some feeds do produce a higher peak in blood glucose, horses don’t rely on the energy derived from their last meal for the next bout of exercise. With this in mind, the time at which you feed is unlikely to improve your horse’s energy levels.
Copyright by Arnd Bronkhorst ©

Avoid soaking/ dampening feed in advance

Although the idea of saving time is always tempting, dampened or soaked feeds can quickly ferment in hot weather so avoid adding water in advance. If using a mash or sugar beet, feed immediately after soaking – quick soaking varieties are ideal!

Safe feed storage

Hot weather increases the risk of mould and grain mite, particularly in cereal based feeds. Feed should be stored in cool (12 degrees Celsius or below), dry and preferably dark conditions. Un-opened bags should be raised off of the floor to allow air to circulate (on a pallet is ideal), have all shrink wrapped removed to prevent sweating and be kept away from walls (allow a gap of 0.5m). If you are only feeding one or two horses, avoid buying in large volumes to help maintain freshness.

For more advice on feeding competition horses contact the SPILLERS Care-Line on 01908 22 66 26 or visit www.spillers-feeds.com

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