Working and performance horses produce a lot of sweat, so they not only lose fluid in sweat but they also lose electrolytes.  Dr. Kathleen Crandell with Kentucky Equine Research indicates that horses should have access to electrolytes year round. For those horses not working hard, loose or block salt may provide sufficient electrolytes. The concern with block mineral is that the amount the horse consumes may not be sufficient to meet his needs.  Sometimes the blocks are contaminated by the environment, especially if they are placed directly on the ground, which affects the taste and limits consumption.

If you have a performance horse, a block is not sufficient as an electrolyte source and daily electrolytes are needed at a much higher level.  The major electrolytes that needed to be supplemented are sodium, potassium, and chloride; although table salt contains sodium and chloride, it does not contain potassium.  However, lite salt does contain potassium so you could add table salt and lite salt to your horse's feed. The amount of electrolytes your horse needs depends on the level of work the horse is doing. There are numerous flavored electrolyte products on the market that can be added to your horse’s feed to encourage him to eat the product. Unfortunately, a lot of these products don't contain enough electrolytes to be effective. The electrolyte paste veterinarians use contains about 9 grams of sodium per dose, which is about the same amount of sodium in one tablespoon of table salt.  However, the commercial paste also contains chloride and potassium as well as minerals calcium, phosphorus, and magnesium.