A: Providing access to or giving salt every day ensures your horse’s maintenance sodium needs are met, which is vital for hydration. So, the first thing to do is make sure you’re feeding sodium chloride and not Lite Salt, which is a blend with potassium chloride that doesn’t provide as much sodium.
Sodium chloride comes in many forms, from plain white blocks to red mineralized blocks to loose forms of the same, plus iodized, sea salt, kosher salt, Himalayan salt, and others. I believe horses should have salt available at all times when not working, and my preference is a plain white salt block unless your horse prefers the taste of another form.
However, many horses do not actively use block salt. A 500-kilogram (1,100-pound) horse at maintenance on a cool day needs the amount of sodium provided by about 28 grams (1 ounce or 2 U.S. Tablespoons) of sodium chloride. This equates to just under a kilogram or 2 pounds of salt a month. So, if your horses aren’t readily consuming this from block form, I suggest adding the daily maintenance amount of salt to their feed, so you know they got it. They should still have access to additional salt, so they can consume more if they want it.
As for the type of loose salt, my go-to is regular iodized table salt, because I find that the small amount of additional iodine is often beneficial in the ration, unless the horse is receiving kelp-based supplements. Kelp-based supplements typically provide several times the daily National Research Council requirement for iodine, and, therefore, I’m not keen in these instances to add more.
The levels of other minerals naturally occurring in mineralized salt are not great enough to make a significant impact on your horse’s ration, except perhaps iron, which is generally in excess in forage-based rations already. Therefore, my motivation for using other forms of salt comes down to your horse’s taste preference and your personal preference. If your horse prefers the taste of sea salt or Himalayan salt over regular table salt, then that makes it a good choice. But know that at the end of the day they’re all providing sodium chloride and one confers very little additional benefit over the other, and most are more expensive than regular table salt.