By Bridget Cook
Electrolytes are salts that are dissolved in a solution—charged ions that act as a medium to conduct electrical pulses between cells and through themselves. These electrical pulses are responsible for bodily functions, such as muscle contractions and nerve impulses. They are in body fluids and are carried throughout the body via the blood. The main electrolytes are sodium (Na), potassium (K) and chloride (Cl).
Horses lose electrolytes through sweat, particularly in hot, humid conditions or during extended periods of work. Supplementing a horse with electrolytes encourages the horse to intake more water to maintain hydration.
“Horses have simple sweat glands, and when they sweat, they lose water and electrolytes in a similar concentration as to what’s in their blood,” says Dr. Hal Schott, of the Equine Medicine Clinician, at Michigan State University.
Horses also lose water across their respiratory tract when they breathe. As the horse’s respiration rate increases during exercise, so does the amount of water it loses as it humidifies across their respiratory tract.
“Over time, if there’s no water replacement, they will end up with a slight increase in salt concentration in their blood,” Schott says, “but if they have free access to water, we don’t see that in blood work because it will go up 1 percent. Then, they’ll drink a little bit, and it will go down. Then it will go up again, so they’ll drink a little bit. We don’t see huge increases in the electrolytes in the blood.”
Electrolyte supplements are available in many forms. They come in pastes that are administered orally. They can be administered intravenously or given in the form of a liquid or powder that is mixed in water or top dressed on feed.
Most well balanced feed rations provide horses doing medium intensity work with the electrolytes they require, while hay provides a good source of potassium.
The horse is comprised of two-thirds water. One third of that is outside of the cells, including in the blood, and the remainder is in the cells. Approximately 660 pounds of a 1,000-pound horse is water. That equates to 80 gallons of water. The most effective way to measure how much water a horse has lost during exercise is to weigh it before and after the exercise. A weight loss of 8.25 pounds equals the loss of one gallon of water.
The average horse should drink five gallons of water a day. A horse in heavy work in a hot, humid climate may drink two to three times that amount. Proper hydration is important for the horse’s overall wellness and can decrease instances of impaction colic.
Should Hot Horses Drink?
A common myth is that a hot horse that’s just been exercised shouldn’t be offered water. Schott and his colleagues found that there was no science behind this statement.
“We found that there was no detriment to giving the horse all the water that they wanted after it has been exercised,” Schott says.
They studied horses that were given free access to water after exercise and compared them to those that were initially given half a bucket of water and then given more water after a 20 minute time period. Both sets of horses drank the same total volume of water.
Drinking Salt Water
Salty water is an alternative to giving a horse an oral paste electrolyte. Horses that are given salt water after exercise and then offered fresh, unsalted water 20 minutes after the salt water will drink more water than horses that are only given fresh water. The salty water increases the salt levels in the horse’s blood and rehydrates the horse. Following a 20-minute time period offer the horse fresh, unsalted water.
Horses that are mildly dehydrated or known to be bad drinkers away from home may benefit from salty water.
“He might be a horse that you offer both salt water and plain water, as well as put some salt in the feed, but don’t do anything different at the show that you haven’t tried at home,” Schott says. “Try it at home for a couple of days to make sure the horse eats it.”
To make salty water that is palatable to the horse, add 1 ounce, or one to two rounded tablespoons of salt to a five gallon bucket of water.
The temperature of the water influences the volume of water the horse will drink.
“Temperature of the salty water affects the horse,” Schott says. “It’s the same for us. Do we prefer an ice cold Gatorade that’s just come out of the cooler or one that’s just cool, but not freezing?”
Horses prefer water that is 68ºF (20ºC). This is the approximate temperature of water coming out of a faucet.
Colder water, 50ºF (10ºC), causes horses to take fewer, shallower drinks and overall drink less water. Hotter water, 86ºF (30ºC), such as water that’s been sitting in a bucket in the sun all day, also has a negative impact on the total volume of water consumed.
Electrolytes, Hydration and Performance
Giving the horse electrolytes does encourage it to consume more water. In a study on eight horses competing in two, 50 mile endurance rides that were two months apart, Schott studied the effect of electrolytes on performance.
On one ride, the horses were given enough electrolytes to replace a small amount of electrolytes that was lost through sweat. On the other ride, horses were given enough electrolytes to replace the entire estimated electrolyte deficit. The horses given the higher level of salt drank more water, but the researchers found no difference in the horses’ race times and recovery.
“Salt helped them drink more, but didn’t affect their overall performance,” Schott says. “Fifty miles takes about six to 10 hours, depending on how fast they go. A horse that gets loped all day before an event probably isn’t doing as much exercise as the endurance horse.
“However, a horse that gets shipped 200 miles the day before, or the morning of, and then goes to the competition to perform—they can get dehydrated. Always use common sense. Horses that are going to be transported all day, remember to stop and offer them water every six hours or so.”
Schott has not found any long-term effects of not supplementing salt intake for performance horses that already eat a well-balanced ration.
“If a horse is eating a reasonable ration, it’s going to be hard for them to get depleted of electrolytes,” he says. “Sometimes people feel that you increase the risk of muscle cramping, but for a horse to do that, you’d have to be going 50 miles a day for five days.
“We did one study on the Outlaw Trail Ride in South Utah where we looked at horses that went 50 miles a day for five days. We found that the horses lost most of their weight the first day or two, and then they were pretty stable after that. They were able to eat and drink to take care of themselves after that.”
Electrolyte depletion in horses is offset due to the reserves that the horse carries in its hindgut.
“Anywhere from 10 to 15 percent of a horse’s body weight is feed material in the gut, whereas for us, it is one to two percent of our body weight. They have a lot of water and electrolytes in reserve to absorb from the hindgut during exercise. During our studies, our goal was only to ever replace between 30 to 50 percent of the estimated loss.”
Electrolyte supplementation is recommended especially in hot, humid conditions. Replacing lost electrolytes is advantageous for horses that are sweating a lot or being trailered in the heat.
Schott recommends top dressing grain with one to two ounces of salt twice per day. Dosage is dependent on how much the horse has sweated out. Two ounces is recommended for horses in hot, humid climates, while one ounce is probably sufficient for horses working in a balmy, 70º environments.
Giving too much salt is not a problem, as excess salt will be filtered through the kidneys and excreted through the urine.
Salt blocks are an easy and useful method of supplementing electrolytes, but many horses won’t eat them, while others will devour them.
“There’s huge variability with salt blocks, so we recommend loose salts in the grain,” Schott says. “You can also use loose trace mineral salts that come in a 50 pound bag.”
Many horse owners also use products like the Equiwinner patch, which is designed to help electrolytes work more efficiently once they are in a horse’s system, to further ensure that their horse’s internal balance is properly maintained.
Bridget Cook is a Texas-based freelance writer and barrel racer. E-mail comments on this article to [email protected].