Is your horse getting enough salt?

But surely too much salt leads to dehydration as the body tries to expel it?

This is a classic "it depends” scenario in biology! It is absolutely true that in a vacuum, salt pulls water toward it (osmosis). If a horse eats a massive amount of salt and cannot find water, they will become dangerously dehydrated as the body tries to flush the excess sodium through the kidneys.

However, in a healthy horse with unlimited access to fresh water, the opposite happens.

Here is why the "salt leads to dehydration" rule works differently for horses than it does for, say, a human stranded at sea:

1. The sodium-water magnet

Sodium is the primary electrolyte that holds water in the bloodstream and in the spaces between cells.

• Without enough salt, the horse's body literally cannot ‘hold on’ to water. They drink, but it passes right through them as thin urine because there’s no sodium to ‘anchor’ the fluid in their tissues. This leads to chronic dehydration.

• When you add salt, the sodium acts like a sponge, pulling water into the blood vessels and keeping the horse hydrated at a cellular level.

2. The kidney ‘flush’

Horses have incredibly efficient kidneys. If a horse eats more salt than they need:

1. The brain triggers an immediate, powerful thirst.
2. The horse drinks a large volume of water.
   
3. The kidneys filter the excess sodium and send it out via urine.
4. The net gain: Because the horse drank so much extra water to handle the salt, they actually end up more hydrated than they were before.

3. When does salt cause dehydration?

• No access to water: If you add salt to your horse’s hard feed, but the horse's automatic waterer is broken or the bucket is empty, the body will pull water from its own tissues to try and process that salt. If this happens for a prolonged period of time, especially if associated with sweating, this can cause ‘salt poisoning’.
• Frozen water: Similarly, in winter, horses often stop drinking because the water is too cold. If you add salt then, you can actually worsen dehydration because they won't drink enough to keep up with the sodium intake.

If your horse is ignoring their salt block, it’s rarely because they don't ‘need’ the salt. Usually, it's a texture issue: salt blocks were originally designed for the rough, sandpaper-like tongues of cattle. Horses have much softer tongues, and licking a hard block can eventually become abrasive or even painful for them.

Switching to loose salt (granular salt) is the most effective way to ensure they get their daily requirements. Here is how to introduce it safely:

1. Mixing with their hard feed meal

The easiest way to get salt into a horse is to add it directly to their existing feed, preferably dampened.

• Start small: Don't dump 2 tablespoons in at once. Start with 1 teaspoon mixed thoroughly into their feed.
• Increase gradually: Over the course of 7–10 days, slowly work your way up to the target amount (usually 2 tablespoons or roughly 20 to 30 grams for a 500kg horse.
• Add water: Dampening the feed helps the salt to dissove and stick to the feed so a fussy eater can't sift it to the bottom and leave it behind.

2. Free-Choice Loose Salt

If you want the horse to regulate their own intake (which most horses are very good at), you can provide loose salt in a separate bucket or feeder.

• Location: Keep it in a covered area (like the stable or field shelter) because rain will turn loose salt into a solid, unappetizing brick.
• The two bucket rule: Some people like to add salt to their horse’s water to encourage drinking, always provide a second bucket of plain, fresh water. Some horses find salty water unpalatable and will stop drinking entirely if they don't have a choice.

3. Choosing the Right Type

You don't need expensive special salts. Standard plain white table salt or iodized salt from the grocery store works perfectly.

• Avoid: Stay away from red mineral blocks or bags if your horse is already on a balanced commercial feed or ration balancer, as these can sometimes provide too much of certain trace minerals.
• Coarse vs. Fine: Coarse salt or livestock-grade loose salt is often preferred because it's less likely to blow away in the wind.

• Personally, I add about a tablespoon of iodised or plain salt to their feeds (less for my TBx else he won’t eat it!). I avoid table salts that have added anti-caking ingredients.
• Then I throw a handful of coarse sea salt and a handful of plain coarse salt into a feed skip each night for them to take what they want.
• There is also a salt lick in a holder in their field and stables. I avoid the ‘Himalayan’ salt blocks nowadays because our ground and water is rather high in iron already.

4. Water is Key

Never provide supplemental salt if the horse does not have unlimited access to fresh water. Salt poisoning is rare, but it almost always occurs when a horse eats a large amount of salt and then cannot find enough water to flush it out.

Julia Williams