It’s a perennial question. Can a horse meet his salt needs from a salt block? In a way, it’s a trick question. There is more than enough salt there to meet the horse’s needs. The real question is will the horse consume all he needs from a block.
A widespread myth is that horses cannot get enough salt from a lick but cows can because their tongues are rougher. A cow’s tongue is rougher (like a cat’s) – but not rough or sharp enough to slice salt off a block! Cows and horses both get salt from a block by dissolving it with their saliva. Same as licking a lollipop.
All herbivores have a strong drive/taste for salt. The sodium in salt (salt is sodium chloride) is the only mineral consistently at very low levels in the natural diet. The drive to eat salt comes from the brain. Salt hunger increases with higher levels of the hormones aldosterone and angiotensin II. The main function of this hormone system is to regulate blood pressure and maintain normal blood volume. Sodium is important for this because of the major role it plays in holding water in the blood stream and the tissues surrounding the body’s cells.
Natural concentrated salt deposits are the beds of ancient seas which have dried up. They may be on the surface (salt flats) or underground, including under the ocean floor. Like all natural mineral deposits they are contaminated to varying extents by other minerals. The table salt you buy in the supermarket has been purified of the contaminating minerals.
Raw salts have different colors depending on their contaminating minerals. Somewhere along the line someone got the bright idea that these basically dirty salts were more desirable, even offered a health benefit because of the myriad contaminating minerals they contain. Problem is, the mineral profile of raw salts has virtually nothing to do with the mineral requirements of your horse.
For example, a typical analysis of one popular “natural” salt’s trace minerals shows it would take 150 kg (330 pounds) of this stuff to meet the average horse’s daily zinc requirement. Toxic fluoride was much higher.
Bottom line is that unrefined salt has zero health advantage over refined table salt. Despite this, you will be paying at least three times more for this raw material than you would for the purified version of exactly the same thing.
Your horse needs about 1 ounce of plain salt daily in cool weather, up to 3 or 4 when sweating. If he won’t eat it freely, add to food or spray on hay to guarantee adequate intake.
Eleanor Kellon, VMD