Dehydration and Electrolyte Losses in the Sport Horse
Dr. Melissa R. Mazan
Water requirements vary greatly according to the weather and the level of work that the horse is doing. For instance, if your horse is exercising in hot, humid weather, he may need 2 to 4 times the minimum amount. A good rule of thumb is that a horse needs at least a gallon of water per 100 lbs of body weight. For your average horse, this equals 10 gallons a day. If you use commercial preparations, look for one that contains approximately three parts NaCl to one part KCl, as well as calcium and magnesium.
If you need to get your horse to drink more, the first, and most important thing, is to make sure that he has continual access to water. Also, horses tend to drink less water in the winter if the water is cold. Studies have shown that horses will drink more water if it is warm or tepid, so, get yourself a water heater, and don't expect your horse to drink the icy cold water.
On the road, some horses are very picky about foreign water. Some experienced competitors advise bringing enough water from home, and getting your horse used to drinking flavored water. Many horses enjoy water flavored with apple juice. Horses will drink more when it is held up to them after and during competition. You should try to offer your horse water in a quiet area, where he will not be disturbed by all the action around him.
One wet-down flake of hay can absorb 1 to 2 gallons of water. If you feed your horse well-soaked hay, you can make a real impact on his fluid consumption. Endurance riders take advantage of this by feeding horses soaked hay before long rides.
It is possible to give your horse too many electrolytes and they can be toxic in excessive amounts. Requirements for salt (NaCl) range from one tenth of a percent of the ingested feed for a broodmare, to three tenths of a percent of the ingested feed for a competition horse. The maximum amount of NaCl that a horse can tolerate before he becomes toxic is three percent of the ingested feed. It would be unusual for a horse to ingest that much salt, as the food containing it would have an unpleasantly salty taste.
If you start to give your horse to many electrolytes, you will start to notice that your horse is urinating frequently, and drinking much more water. Some veterinarians do not recommend adding electrolytes to water. If you choose to supplement this way, it is VERY important that you also always offer your horse a bucket of water with NO additives. Your horse cannot, and should not, take in enough water with electrolytes to sustain his fluid requirements, and will become dehydrated if you do not give him access to plain water. In general, it is a better idea to supplement electrolytes in the feed, rather than in the water.
If you would like an inexpensive and effective solution, all you have to do is buy Lite salt (this is just KCl), and ordinary table salt. Mix them at a ratio of three parts table salt to one part Lite salt.
The amount you give depends on the weather and the horse's level of exercise. In general, horses that are not sweating excessively need two ounces per day of this mixture. Horses who are sweating in hot, humid weather need 3 to 5 ounces of this mixture.
In order to ward off electrolyte losses, give your horse approximately two ounces of electrolyte supplement a few hours before competition. If the competition will be long (such as an endurance ride), plan to give the same amount every 1/2 hour to 1 hour.
Don't give your horse dry hay after competition – it will soak up water that the horse needs elsewhere in the body.
Horses can generally be supplemented from 1 to 2 ounces of salt per day. Most commercial grains contain from 0.5 percent to 1 percent added salt, in addition to potassium and calcium. Because horses eat considerably more hay and other forage than grain, the horse's total ingested salt will be less than 1 percent. This is more than adequate for a pleasure horse, but is usually not enough for heavily exercising horses.
Salt can be supplemented in the form of a salt block (a trace mineral block is best), or as free salt added to the grain. This works best with a grain that has some sort of binding agent, such as molasses. The amount of salt your horse gets from a salt block depends on whether your horse has a taste for the salt block. Studies have shown that some horses fail to take in even the minimal requirements if they are simply given a salt block.
Horses that have done short, extreme bursts of exercise need to be carefully cooled down, and should be given frequent, small sips of water.
Horses that have done long, moderate exercise (such as endurance horses), should be allowed to drink water during and immediately after competition.
Although electrolyte solutions are not the best way to deliver electrolytes on a daily basis, they are appropriate after competition. As a matter of fact, your horse will be much more likely to drink an electrolyte solution during or after competition, rather than before. However, your horse needs water, not just electrolytes.
Horses that are moderately to severely dehydrated need veterinary attention. The attending veterinarian will treat with intravenous fluids and fluids given with a nasogastric tube.