Sodium deficiency leads to dehydration in horses! The electrolyte most likely to be in short supply in horses is sodium. You are better off providing extra sodium rather than too little, as a healthy horse can easily excrete the excess if plenty of fresh water is available.
Table salt is 40% sodium by weight (plain old iodized salt from the grocery store) – 2 tablespoons mixed with wet feed or sprinkled over wet hay fulfills the baseline daily sodium requirement (before sweat losses) for a 1000 lb horse.
In hot weather, don’t count on a salt block to supply enough sodium! Sweat losses can more than double a horse’s sodium requirement in hot weather, even without exercise. To help prevent dehydration in hot weather, consider feeding up to 4 tablespoons of table salt per day – mixed with wet feed or sprinkled over wet hay. Also offer your horse an electrolyte solution as well as plain water. (Source: Nutrient Requirements of Horses: Sixth Revised Edition, National Academy of Sciences).
If your horse is dehydrated, don’t force-feed concentrated electrolytes unless the horse is drinking freely. Instead, offer an electrolyte solution in addition to plain water, or mix table salt or electrolytes with feed and add water until soupy.
Here’s a recipe for a homemade electrolyte solution that’s an inexpensive and effective alternative to commercially-formulated electrolyte powders:
Homebrew Electrolyte Solution for Horses
- 1 oz (2 tbsp) table salt (sodium chloride)
- 2 oz (4 tbsp) lite salt (sodium chloride and potassium chloride)
- 1 oz (2 tbsp) baking soda (sodium bicarbonate) or 10 Alka-Seltzer tablets
Mix with 5 gallons of water and offer alongside plain water to prevent dehydration, or to treat dehydration in a horse who is drinking. If needed, add flavor with alfalfa pellets, oats, powdered drink mix, or molasses. (Dr. Kellon’s Guide to First Aid for Horses, 2005)