horse drinking water

Dehydration in Horses

Dehydration is a serious yet often overlooked condition in horses that can have significant health implications if not properly addressed. Water is essential for life and comprises about 60-70% of the bodyweight of the adult horse. In the healthy horse, average daily water intakes are around 50ml per kilogram of bodyweight per day but this may vary significantly between individuals and can be affected by diet. For example, horses at grass for longer periods usually consume far higher levels of water than stabled horses since grass is around 80% water, whereas hay is only about 15% water and haylage typically between 30 and 50%. This is why horses on plentiful lush pasture may not drink as much as the stabled horse.

The horse may lose fluid via four different pathways – through the faeces, the urine, through moisture produced when the horse breathes, and through sweat. Lactating mares can also lose fluid through milk production, which is why it’s so important to make sure the broodmare always has plenty to drink.

There are many factors that may contribute to dehydration in horses including:

  • Excessive sweating, caused by strenuous exercise, travel or increased temperatures
  • Failure to drink – animals that are under stress, especially those affected by disease, may be more likely to fall into this category
  • Health problems such as chronic diarrhoea – veterinary attention should be sought in these situations

Signs of Dehydration in Horses

Dehydration in horses not only affects their performance, but it can also lead to serious health problems if not managed and may even be life-threatening. Early symptoms of dehydration can sometimes be confused with other problems, but the typical signs to look out for include:

  • Poor performance especially early onset of fatigue when working
  • Lethargy and depression
  • Darker-coloured urine
  • Reduced urination
  • Dry gums

Although using the ‘skin-pinch’ test to see how quickly it returns to its usual position is often cited as a good indicator of dehydration in other species, its validity and repeatability in the horse is poor, with the age of the horse, the position of testing, the side of the horse and coat moisture all shown to have a significant impact on the result (Pritchard et al., 2008). This method should therefore not be relied upon to determine a horse’s hydration status.

What are electrolytes?

Electrolytes are frequently the cause of confusion and deliberation – horse owners often wonder whether they are needed and when to use them. Electrolytes are minerals that, once in the body, dissolve and gain a positive or negative charge. The horse’s nervous system works via electrical impulses to control the muscles, and so the balance of electrolytes within the horse’s body can influence muscle function, as well as affecting the movement of fluid into and out of cells. Other bodily functions can also be affected, including digestion. The main electrolytes for horses are sodium, potassium, chloride, magnesium and calcium.

Because electrolytes are water-soluble, they are lost through urine and sweat. Sweat losses can be particularly significant for those in hard work, but also for those who are working hard relative to their fitness level or ability. Horses that appear to get tired towards the end of their work may well be doing so as a result of electrolyte losses through the sweat, particularly if they are working in hot and humid conditions. Because electrolytes aren’t stored in the body, horses who sweat regularly either through work or travel might require a daily electrolyte supplement.

powder supplement

Horse owners often ask why electrolytes aren’t just added to a feed so that supplementing them isn’t required. Because electrolytes are salts, if they were included in feeds at sufficient levels to replace what is lost when working, the feed would taste very salty and would probably be unpalatable to most horses and ponies.

For this reason, electrolytes tend to be supplied as supplements that can be added to the feed or water. If adding electrolytes to water, it is recommended that plain water is also made available because some horses might take a while to get used to drinking the water with the electrolytes added, which could result in dehydration. If adding to the feed, the feed should have water added to make it sloppy prior to feeding.

Even if your horse isn’t in hard work but typically sweats heavily through excitement or travel, for example, using an electrolyte supplement is still likely to be beneficial. Remember that heavy breeds such as cobs and natives are adapted to surviving in colder climates and so often have to work harder to remove the heat from their bodies when exercising. This often means they sweat more than a lighter breed doing the same level of work and so could lose more electrolytes as a result.

In serious cases of dehydration, veterinary attention will be required to administer fluid therapy to rehydrate the horse and in this situation, electrolyte supplements formulated to maintain the balance in the healthy horse would not be appropriate.

What’s the difference between electrolytes and table salt?

Table salt is a combination of sodium and chloride and so an electrolyte supplement for horses should ideally include potassium, calcium and magnesium in addition to more effectively replenish the minerals lost in sweat. Although salt licks or free access salt can be helpful in contributing towards the horse’s requirements, it is important to note that horses are actually very poor at self-regulating their salt intake so it is impossible to ensure that a suitable amount will be consumed each day to meet their needs. Most horses will benefit from added table salt within the bucket feed on a daily basis, but for those who sweat regularly, a specific electrolyte will be of greater benefit to replenish levels that are being lost.

You can lead a horse to water… but how can we encourage horses to drink?

It’s not uncommon for horses to be reluctant to drink when they’re away from home, which could be due to the taste of the different water or as a result of the stresses of travel and competition. Some horses also don’t drink much even at home. Using buckets of water rather than automatic drinkers can be preferable when it comes to monitoring intake as it is easier to check how much is being consumed.

horse drinking water in field

Below are some top tips for encouraging horses to drink:

  • Ironically, horses often prefer the water from the field tank, as opposed to fresh from the tap, so if they don’t normally drink much out of the bucket while they are in the stable or away from home, try filling it with water from the tank in your field. When travelling or staying away, bringing their normal bucket from home can also be helpful.
  • When travelling, take your own water from home where possible as your horse will be used to its taste.
  • If taking your own water isn’t possible, try flavouring your water at home with a little bit of fruit cordial or food flavouring in advance to tempt them, and then use the same flavour when you stay away to hide the change of water. Flavours can also be used on a longer term basis to tempt horses who are continually poor drinkers.
  • In cold weather, mixing some warm water into their bucket may encourage them to drink as it may be more appealing than ice cold water from the outside tap or trough.
  • Offering a soaked feed is another way to increase water intake that doesn’t require the horse to actually drink from a bucket. Electrolytes can be added to Dengie Alfa-Beet which must be soaked prior to feeding. Alternatively, water can be added to a couple of scoops of your horse’s normal chopped fibre to make it sloppy and allow water intake to be increased in the form of a bucket feed, without having to purchase a specific mash if it’s not part of your horse’s usual diet. Electrolytes can also be added to make your own soaked feed for aiding recovery.
  • Consider using haylage rather than hay – a true haylage will have at least 35% water and so will provide more water than hay. As the horse consumes so much more forage than bucket feed, this can have a significant impact on their total daily water intake.
  • Increase grass turn out if possible – grass is around 75-80% water so some time out grazing will increase water intake. Obviously this isn’t feasible if the horse is prone to laminitis as the grass may present a greater risk to their health, but it could be an option to consider for some individuals.

How to cool down a horse in hot weather

Walking can help to cool your horse, by increasing the movement of hot air from the body and replacing it with cooler air. This will help to bring the horse’s temperature and respiration rate down but it also has another important function. The lymphatic system is crucial to the horse’s health, performance and recovery, and consists of an extensive network of vessels and nodes that help to maintain fluid balance and cellular health. After exercise, the lymphatic system clears the waste generated by cells that have been working hard to supply the fuel that powers performance. A cool down for around 20 minutes helps the lymphatic system to work efficiently.

It is also important to physically cool the horse down after exercise. Cold water applied all over the body has been shown to be one of the most effective ways to keep horses cool. It is important to ensure the water temperature is cooler than the horse so that heat can be lost through both evaporation and convection (transfer of heat from the body to the air). Ensuring the horse is in the shade and out of direct sunlight will also increase convection cooling.

horse wash down

How to keep your horse hydrated in cold weather

Your horse should always have access to fresh, clean drinking water, but when temperatures drop, life can get difficult as water buckets or drinkers can freeze over. For this reason it’s essential to regularly check your horse’s water to break and remove any ice. Floating a tennis ball in the trough or buckets can help to reduce ice formation and allow your horse to still access their water supply as the bucket shouldn’t become totally iced over. In very cold temperatures though this still may not be sufficient, so water supplies should be checked frequently.

Some horses will refuse to drink very cold water so adding hot water to make the bucket or trough water lukewarm or tepid may encourage drinking. A previous study found that horses drank about 40% more when heated water was provided compared to ambient near-freezing water (Kristula and McDonnell, 1994). Since an insufficient water intake can increase the risk of dehydration and colic, it’s really important to monitor your horse’s intake especially over the colder months to ensure they are consuming enough.

soaked pellets

Other ways to increase moisture intake include feeding haylage or soaked hay and wet feeds. Providing a soaked fibre feed, such as Dengie Alfa-Beet, is a great way to provide an additional source of moisture to aid hydration in the winter. Some horses will happily drink a solution of electrolytes – which can also be made with warm water – to improve hydration levels. Make sure they also have access to fresh drinking water at all times when being given electrolytes.

The Importance of Fibre

As well as ensuring your horse is consuming plenty of water and adding electrolytes to aid hydration, the importance of a high fibre diet should not be underestimated. In addition to its numerous benefits for digestive health, feeding plenty of fibre also helps to maintain hydration as it acts as a reservoir for water in the hind gut, providing reserves that the horse can draw from when required. Some horses can back off their forage when away from home, so feeding chopped fibres in the bucket can be a useful alternative. Suitable options from the Dengie range include Meadow Grass with Herbs and Oil or Meadow Lite with Herbs – just make sure these are introduced to your horse’s ration gradually in advance.

Top tips for keeping your horse hydrated:

  • Ensure fresh clean water is available at all times.
  • Monitor your horse’s water intake, especially during periods of colder weather or when away from home.
  • If your horse doesn’t like drinking fresh tap water while stabled, try filling a bucket from the field trough.
  • Adding cordial or food flavouring to water can help tempt fussy drinkers.
  • Using soaked feeds or adding water to a chopped fibre feed can help aid hydration without the horse having to drink from a bucket.
  • Adding salt or electrolyte supplements can help to replace what is lost through sweating.
  • Feed a high fibre diet as fibre acts as a fluid reservoir in the horse’s hind gut so can also help to keep them hydrated.

References

  • Pritchard et al., (2008) Validity of indicators of dehydration in working horses: A longitudinal study of changes in skin tent duration, mucous membrane dryness and drinking behaviour. Equine Veterinary Journal, 40(6), pp. 558-564.
  • Kristula and McDonnell (1994) Drinking water temperature affects consumption of water during cold weather in ponies. Applied Animal Behaviour Science, 41(3-4), pp.155-160.