Australian cattle and sheep farmers have noted better weight gain, under normal weather circumstances, and less weight loss during periods of heat. 
This of course translates directly to better market value.  If you have horses, you probably aren’t raising them for slaughter, but heat and cold stress still affects your horses’ condition, recovery time, and trainability.  If you can lessen the stress from heat and cold, you get better performance from your horse and a better price when you go to sell it (and we all know what a challenge that is these days)!

Other health benefits include:

• Regulating the water content throughout the body. Because the Himalayan salt is so pure, so free of toxins, and not baked at 1200 degrees, the crystalline structure doesn’t require nearly as much water or energy to absorb as
  the ‘regular’ stuff.  This means your horse doesn’t bloat on
  water, dilute his electrolytes, and YOU don’t waste as much bedding – or time and energy cleaning his stall!
• Promoting a healthy pH balance in your cells, particularly your brain
  cells.  As it doesn’t use as much water, the pH remains right where it should be, which allows them to function with less energy wasted, and allows your horse to perform better, no matter what he’s doing.
• Promoting blood sugar health and helping to reduce the signs of aging.
• Assisting in the generation of hydroelectric energy in cells in your horse’s body. Electrolytes are critical for the movement of electrical energy in his body. Salt, as well as other minerals helps create that. When the
  horse can utilize the structure easily, it doesn’t require as much.
• Absorption of food particles through your intestinal tract.
• Supporting respiratory health.
• Promoting sinus health.
• Prevention of muscle cramps. When the electrolyte balance is off, muscle spasms occur.  Getting enough salt – and the proper amount of water – keeps that from happening.
• Promoting bone strength. Getting the proper amount of the correct minerals – Calcium and phosphorous, among others – help to build strong bones.
• Regulating the sleep — it naturally promotes sleep. Getting the proper amount of calcium and magnesium in the diet helps calm animals, and helps them to get the proper amount of sleep, so that they can train and compete at their best.  The minerals in HorseSalt Brand Himalayan Salt are easily absorbed by the system.
• Supporting the libido is especially important for breeding stock.  Need we elaborate?
• Promoting vascular health.  When the proper amount of water is in the system, blood pressure is less of an issue.  As this salt helps regulate the amount of water in the system, it helps with this.  Also the minerals found in it help strengthen the muscles, and reduce the inflammation often found in patients with blood pressure issues.
• In conjunction with water it is actually essential for the regulation of blood pressure.

Here is a pdf with the mineral analysis of Himalayan salt.  This is likely to vary a bit from piece to piece, as concentrations differ, but this is a good starting point to understand what is going into your livestock.