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:
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:
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.
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.
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.
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.
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.
Below are some top tips for encouraging horses to drink:
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.
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.
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.
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.