The importance of water.

We talk a lot about our horses' diets—whether they're forage, feed, biotic supplements, etc.—and we pay less attention to the importance of the water we provide. The truth is that water is the basic priority for a horse's life; only the air they breathe surpasses it in importance as a fundamental nutrient for life.

Drinking water from Lake Montcortès.

Water is involved in everything from pumping your heart and digesting food to lubricating your joints, filtering waste through your kidneys, and, very importantly, regulating your body temperature .

While we cannot control the amount of air available, we can control the quantity and quality of water we provide to our animals.

A horse's body contains 65–75% water. Horses maintain their body fluid balance by drinking water or eating moist foods such as grass, as well as through the metabolism of proteins, carbohydrates, and fats. Horses lose water through the excretion of urine, feces, and sweat, as well as by exhaling while breathing. A lactating mare also loses fluids through milk secretion. Water can also be lost through illness; diarrhea, for example, can be extremely dangerous for foals; they can lose water too quickly and disrupt their body fluid balance.

The amount of water a horse needs to consume per day is directly related to the amount of water the horse loses per day. A horse needs approximately three to eight liters of water per 100 kilograms of weight.

Of course, diet also plays a role. Water is the basis of all nutrition; it provides saliva, stomach acid, enzymes for the small intestine, and the fermentation capacity of the large intestine.

Horse surrounded by fresh grass

Fresh grass has approximately 60–80% moisture, which means they obtain a substantial amount of water while grazing. In contrast, grains, concentrates, and baled hay contain much less moisture, meaning horses need to drink more to meet their water needs.

One of a horse's biggest water losses is manure. When a horse consumes forage, it is digested through fermentation in the large intestine, in a fairly liquid environment that allows for optimal bacterial growth. Forage consumption encourages water intake to maintain this environment. Fresh grass in pastures contains a much higher moisture content compared to dry feed, so it's not surprising that horses visit the water trough less frequently when grazing lush forage compared to when fed hay.

In addition to its nutritional function, water transports oxygen to every cell (and carbon dioxide from it), allowing the diffusion of these gases across cell membranes. It transports hormones, immunoglobulins, antibodies, and all the components that regulate these essential metabolic factors. It is essential for secreting substances on the external surface of the skin and hair, to maintain a barrier against infections, parasites, and other pathogens.

Mare urinating

Obviously, urine also contributes to water loss in horses, although it is the most variable type of water loss in horses. Some horses simply consume more water than others, so they will excrete more dilute urine to eliminate excess water from the body. On the other hand, if the horse's water needs are not met, the kidneys will act to limit water loss and concentrate the urine.

Of course, the weather can also affect water consumption. Horses generally consume more water during the hot and humid summer months. But some horses even drink more water in winter than in the hot summer because the quality of forage is generally not as good as in the lower humidity of summer.

Sweaty horse

Sweat represents a tremendous variable in a horse's water loss, dependent on both temperature and exercise. Compared to other species that rely primarily on respiratory cooling or panting for cooling, horses are more similar to humans, as both dissipate heat through sweating and evaporative cooling.

Rising ambient temperatures can increase evaporative losses by between 45 percent and almost 400 percent of a horse's normal water losses. Adding exercise to environmental losses can quickly lead to dehydration and heat stress if water losses are not replaced.

The good news is that horses, through training or adaptation to their environment, become more efficient at dissipating heat and begin to minimize their water losses.

Colt suckling

Lactating mares also experience significant water loss through their milk. The amount of milk produced can be extremely variable between mares, averaging 2 to 3 percent of their body weight per day. This will increase their water requirements by 50 to 75 percent more than normal. Lactating mares also have very high energy demands on their bodies, which also increases their feed intake. We've already discussed that as feed intake increases, the horse must increase its water consumption to keep digestion flowing and counteract water losses through manure.

The stages of a horse's life cycle are also important. In the case of foals, for example, their initial water needs are met by the mare's milk. But, when they are around one month old, they begin to eat a fairly significant amount of feed and nibble on dry forage; their water intake can reach 4 liters per day at that point. When they move on to consuming more dry feeds, such as hay and grain (and less milk), their water intake increases. Conversely, an older, more mature horse that has had less exercise may have a lower water intake.

Several circumstances can cause water deficiency in horses, including unpleasant taste, lack of water offered, or loss of thirst due to exertion.

Lack of water puts a horse's vital systems at risk. A horse can live for about a month without food, but within 48 hours of not having enough water or insufficient intake, it is likely to begin developing problems such as colic, impaction, lethargy, or other life-threatening conditions.

Increasing levels of dehydration will affect the bloodstream, reducing fluidity, which can lead to heart failure, oxygen deprivation, and multiple organ dysfunction. Muscle activity is impaired. Finally, the cells themselves become flaccid and lose moisture, leading to biochemical breakdown. Extreme dehydration can lead to death fairly quickly.

Checking for dehydration

Signs that a horse may be dehydrated include weakness, depression, sunken eyes, dry mucous membranes, slower capillary refill time, and an increased heart rate. A quick way to check your horse's hydration level is to pinch the skin near the base of the horse's neck for two seconds. If the skin returns to normal almost immediately, then the horse is not severely dehydrated. However, if the skin remains in the pinched position, the horse needs water.

Drinking water from the watering trough.

The horse will drink intermittently for only a few minutes each day to quench its thirst, and it modifies its water consumption pattern depending on both the source and availability. Each time it drinks, it first dips its nose into the water to take a long drink and then takes several small sips.

They will not drink if the water is too cold, frozen, or too warm, and water bowls should always be kept clean to prevent the development of parasites or algae.

So they should never be without access to fresh, clean, and palatable drinking water, and in horses that live in groups or herds, monitor the pecking order. If you suspect that one or more horses are being chased away from the watering trough, you should

consider adding a second watering trough