Dehydration predisposes horses to many problems
Water is the most important nutrient for a horse. A lack of water is fatal faster than a deficiency of any other nutrient. Adequate water intake is essential both for regulating the horse’s fluid balance and for normal digestive function. Too little fluid leads to poor wellbeing and may predispose the horse to, among other things, impaction colic, performance issues, and reduced feed intake. About 60–70 percent of a horse’s body is water, and dehydration of more than 10 percent can, in the worst case, be life-threatening. For this reason, adequate drinking and proper fluid balance are a cornerstone of wellbeing both in summer and in winter.
A horse’s fluid balance functions properly when water intake and water loss are equal. Drinking too little affects, among other things, feed intake and performance. Water affects metabolism and therefore also recovery: if drinking or fluid intake is insufficient, the removal of waste products from the body slows down. This can cause, among other things, various muscle-related problems.
Water is lost from the horse through manure, urine, breathing, evaporation from the skin, and sweating. The amount of drinking water a horse needs depends on the type of forage used in feeding, the amount and type of work, the ambient temperature, and the horse’s size. Dry hay contains about 14 percent water and haylage about 50 percent. Horses eating dry hay therefore need more water than those eating moister haylage. In addition to the forage type, drinking is also influenced by the amount of forage. Studies have found that actively working horses that receive only forage drink more than horses that receive concentrates in addition to forage. This is because the less digestible fibers in forage bind fluid from elsewhere in the body into the gut, and therefore a large amount of water also leaves the body in manure. Pasture grass contains more water than dry hay or haylage—up to 80 percent. Thus, 40 kg of pasture grass can contain as much as 32 percent water.
The need is tens of liters of water per day
A horse needs tens of liters of drinking water daily. During the indoor feeding season, the requirement for an adult horse at maintenance is about five liters of water per 100 kg of body weight. Thus, for example, a 500 kg horse needs about 25 liters of drinking water per day. For a horse doing moderate to heavy work, the requirement is much higher—up to twice as much. A 500 kg horse can sweat 10–15 liters per hour during training, and a lactating mare loses as much as 2–4 percent of her own body weight through milk. Foals are especially prone to dehydration. A foal about one month of age drinks about 4 liters of water per day in addition to milk, and later the amount increases to five liters.
Air temperature has also been found to affect how much water horses drink. Temperatures below –8 °C have been shown to reduce horses’ water consumption by 6–14 percent, and hot air (above 30 °C) to increase daily water consumption by about 80 percent.
Electrolytes, mashes, and flavoring the water
When sweating, a horse loses large amounts of electrolytes, which in turn can disrupt the regulation of fluid balance. Feeds generally contain little sodium, so correcting sodium losses is the biggest challenge associated with sweating. Studies show that horses generally do not get enough sodium from a salt lick alone, which is why it is recommended that horses also be given salt in their feed to compensate for losses. For competition horses that sweat a lot, this means about a 100-gram salt supplement after a performance, and for others about 8 g per 100 kg of body weight. Hot weather also affects the amount of electrolytes lost through sweat. If it seems that a horse is drinking poorly, you can try to encourage more drinking by flavoring the water with, for example, different mashes or juice. Some horses also like the taste of mildly salted water. Teaching a horse to drink flavored water is also a good way to ensure drinking on competition trips, when familiar-smelling and familiar-tasting water is available.
Water available with every meal – horses drink the most in the afternoon
Even mild dehydration takes a few days for a horse to recover from, and horses that consistently drink too little are at risk of kidney damage. According to research, a horse should have water available with every feeding, because horses drink after eating. According to one study*, the most drinking occurred within three hours after feeding. While eating, horses produce large amounts of saliva and gastric acids for digestion. This production stimulates the thirst hormone, which is why horses should always have access to water after eating. One study found that horses drank the least early in the morning and the most in the afternoon. Drinking frequency is also influenced by temperature; in hot weather, a horse drinks every few hours. In addition, horses often prefer to drink after exertion. However, the sensation of thirst can pass fairly quickly, so it is best not to delay offering water after exercise.
Water temperature matters
A horse drinks a greater volume of water warmed to +19 °C than cold water, so the temperature of the available water really does matter. Low water intake can have many causes, such as water with an unusual taste or smell, or water that is too cold. Especially in older horses, cold water can make their teeth ache. By offering warm water, especially in winter, horses’ water intake can increase by as much as 40 percent according to studies*. Preventing water pipes from freezing in winter is ensured through sufficient insulation and proper installation depth. Even in winter, the temperature of drinking water can be influenced by installing a heating cable along the water line, which not only prevents freezing but also raises the water temperature—this increases horses’ drinking and thus reduces the risk of impaction colic. In addition, you should ensure that the drinking bowls provide a sufficient flow rate for the horse, 8–10 liters per minute, so that horses can drink enough. According to a study conducted at the Swedish University of Agricultural Sciences, a flow rate of 2–3 liters per minute is not sufficient, and horses generally do not drink enough in that case. For a poor drinker, it is also worth offering water in a bucket, because one study found that when given a choice, horses preferred drinking from a bucket rather than a drinking bowl.
Signs of dehydration
If you suspect your horse is not drinking enough, signs of dehydration may include, for example: reduced appetite, decreased manure output, a drier-than-normal mouth, dry manure, and the horse appearing sleepy or lethargic.
As useful rule-of-thumb figures for adequate water intake as summer approaches (temperature around 20 °C), the following can be used:
- maintenance horse 25 l/day,
- pregnant mare 31 l/day,
- lactating mare 51 l/day,
- horse doing moderate work 41 l/day, and
- 1-year-old foal 19 l/day.
See all Chia de Gracia products for maintaining fluid and electrolyte balance.
Sources:
Hevostietokeskus
Kristina Dahlborn, Hippocampus dagarna 2005
Drinking water temperature affects consumption of water during cold weather in ponies
Effect of water supply method and flow rate on drinking behavior and fluid balance in horses
