Salt, chemically known as sodium chloride (NaCl) is fundamental to your horse’s well-being. Even horses who are not working require a daily supply. Sweating from work, or heat and humidity increases the need. It also increases the need for other electrolytes, such as potassium, calcium, and magnesium. Forages and other feedstuffs usually provide these additional minerals. Or electrolyte supplements can be used. But there is an important distinction between feeding plain salt and adding electrolyte supplements to the diet. Let’s start by examining salt.
Salt is necessary for key body functions that have nothing to do with the weather. The sodium portion of NaCl is needed for proper muscle contraction, including the heart muscle, as well as nerve impulses throughout the body and brain. If your horse is getting plenty of forage every day, he is getting many key electrolytes, except sodium. Hay and pasture are very low in sodium. That is why salt needs to be easily accessible.
The chloride portion assists with balancing the blood pH and water flow in and out of the cells (osmotic pressure). It is needed for potassium regulation, allowing for proper muscle contraction as well as water balance. During exercise or hot/humid conditions, large amounts can be lost from heavy perspiration. Fortunately, forages (pasture and/or hay) are high in chloride.
Another significant role of chloride is the production of stomach acid, known as hydrochloric acid (HCl). HCl is needed to start protein digestion. Without enough HCl, horses can become malnourished due to an inadequate pool of available amino acids with which to produce body proteins (such as those found in muscles, joints, skin, hooves, vital organs, and other tissues, as well as enzymes, antibodies, and some hormones).
An important aspect of HCl worth noting is its role in the immune system. Horses normally eat off the ground, ingesting beneficial but also harmful microbes. HCl serves as the first line of defense against potential infections.
A full-sized horse (1100 lbs or 500 kg) requires a maintenance level of one ounce (two level tablespoons or 30 ml) of salt each day.
How to add salt to your horse’s diet. The best way to meet your horse’s salt needs is to offer granulated salt free-choice in a small container. If your horse ignores it, it may be necessary to add salt to your horse’s meals. Before doing this, calculate the amount of sodium from any commercial feeds or supplements. You may need to contact the manufacturer for this amount since it is often is not included on the label. Your goal is to provide approximately 12 grams of sodium per day to a full-sized horse. Each teaspoon (5 ml) of table salt contains 2 grams of sodium, so calculate accordingly. However, for palatability, limit the amount to no more than 1 tablespoon (3 teaspoons) per meal.
Salt blocks or unrefined rocks should also be available for additional needs. During periods of heavy perspiration, one ounce per day may not be enough. Salt blocks or rocks can offer additional salt during these times. However, keep in mind that these were originally intended for cattle, which have scratchy tongues. Horses, with smooth tongues, may develop irritations when licking too long. Therefore, though good to have around, they generally do not meet the daily requirement and are only useful for supplemental needs.
Salt offered in bulk at many feed stores may contain “prussic acid,” so check the label before purchasing. Prussic acid is often added as an anti-caking agent and is the common name for “hydrogen cyanide.” While cyanide can naturally occur in minuscule concentrations in feedstuffs, I do not recommend deliberately adding cyanide to your horse’s diet.
Common sources of mined salt deposits are those from Salt Lake in Utah[i] as well as Himalayan salt. Himalayan salt is obtained from a salt mine in Pakistan, about 300 miles away from the Himalayan mountain range. It contains a vast variety of trace minerals and many horses enjoy the rocks. When choosing a product, it is always preferable to use one that offers a guaranteed analysis.
In nature, salt exists in loose form, accumulating on rock surfaces and sediments near salt water sources. Wild horses often travel miles to find salt.
They also obtain salt, and trace minerals simply by eating many types of plants, contrary to the same daily diet our horses experience. Offering a naturally mined salt rock or coarse granulation is one way to offer the domesticated horse the variety found in nature.
The iron content in Redmond rocks, for example, is 300 ppm[ii] and Himalayan rocks contain approximately 39 ppm.[iii] If you have an insulin resistant or a cushingoid horse and are trying to avoid added iron in the diet, these numbers may sound concerning. But they shouldn’t be. It’s best to put it into perspective: Most forages contain between 70 and 250 ppm of iron. If your horse consumes 22 lbs of this forage per day, that equates to 700 to 2500 mg of iron per day. One ounce of Redmond Rock contains 8.5 mg of iron and one ounce of Himalayan salt provides 1.1 mg of iron. So, the contribution of iron from these salt sources is minuscule compared to what a horse normally consumes from pasture or hay.
Your horse can lose up to four gallons of perspiration an hour when exercised in hot, humid conditions. Sweat is predominantly made of sodium, chloride, and potassium, with lesser levels of magnesium and calcium, all responsible for keeping your horse’s heart beating, the gastrointestinal tract moving, kidneys working, as well as maintaining almost every biochemical reaction. Without them, the horse can become weak and may collapse.
Electrolyte supplements contain some NaCl, but not enough to meet your horse’s daily need for salt. Consequently, if used, they should be given in addition to salt. They are not meant to replace salt. Instead, they are designed to help replace some perspiration losses and are to be used on an “as-needed basis” following exercise or periods of excessive perspiration.
Read the label. Many electrolyte supplements contain sugar as the first ingredient. It is typically added for improved palatability but is not necessary. Horses normally enjoy the flavor of salt. Your supplement should contain approximately 13 grams of chloride, 6 grams of sodium, and 5 grams of potassium along with lesser amounts of calcium, magnesium, and perhaps some copper (to promote healthy red blood cells).
Hay provides almost no sodium, but plenty of potassium and chloride. When a horse sweats for two hours or longer, he will lose significant amounts of chloride. Electrolyte supplements designed to replace perspiration losses offer some, but not enough. The key is to give your horse a head start on chloride blood levels before exercise begins. Fortunately, this is easy to do since grass hay is high in chloride. As little as 9 lbs will provide enough chloride to get your horse through his exercise session. Fresh pasture grasses also contain chloride, but your horse would have to graze for a several hours to get the same amount found in hay because pasture is mostly water.
How to use an electrolyte supplement. Assuming your horse is in good sodium standing before the hot, humid conditions set in, you can supplement electrolytes on an as-needed basis. Follow the label instructions. You can add it to one or two gallons of water, followed by plenty of fresh water. You can also add electrolyte supplements to your horse’s feed, but if you’re already adding salt, you’ll make it unpalatable. Electrolytes also come in a paste version, which is fine, but don’t forget to immediately follow it with fresh water. Important to note: Never add electrolytes to your horse’s only water supply. Plain water must always be available.
Furthermore, always allow your horse to eat something before giving him an electrolyte supplement. The risk of developing ulcers is very real if electrolytes are given on an empty stomach.
Oddly, horses do not always know that they’re thirsty. This has to do with the hormones that regulate sodium and water levels in the blood. If your horse does not drink enough water, his blood will become concentrated with sodium. The hormone that manages this problem is called antidiuretic hormone (ADH). An anti-diuretic causes less urination. Therefore, ADH will tell the kidney that it needs to retain water in order to dilute the blood; your horse will urinate less, and his urine will be more concentrated. His blood, on the other hand, will become more diluted due to water retention and he won’t know that he’s thirsty.
But there’s a flip side to this situation. Let’s say your horse is getting enough water, but not enough salt (sodium). Low sodium in the blood causes another hormone to come on the scene — aldosterone. This hormone delivers a different message to the kidney. It says, “Don’t let any sodium leave!” When the kidney holds on to sodium, it excretes potassium in its place.
This would lead one to think that the horse needs more potassium. But it’s just the opposite — he needs more sodium; not enough sodium is what caused the potassium loss in the first place!
In both cases, the hormones try to maintain balance between water and sodium, so your horse may not sense that he is dehydrated. He will not realize that he either needs more salt, or more water. Why, you ask? Well, this is a survival mechanism. But as caring horse owners, we do not want our horses to go into “survival mode.” We want them to thrive.
The solution is to provide adequate sodium so your horse will drink enough water. Even mild dehydration can be harmful — muscles get tired and can tie-up, and colic risk increases due to depressed intestinal motility. To check for dehydration, most folks pinch a fold of skin on the horse’s neck to see if it goes back into place. But frankly, the best barometer of hydration is to offer him a drink. You “cannot make him drink” as the old saying goes, but if he does drink, then you know he needed it. If his thirst mechanism is out of whack, feed him something he enjoys and add some salt to it, while keeping water nearby.
Give your horse salt – either plain, white salt or a natural salt that has at least 93% NaCl. Potassium and chloride requirements are met by feeding hay, but one ounce of salt will provide the sodium he requires for maintenance. Electrolyte supplements can be given when there is excessive sweating, but only when your horse starts out in good sodium balance.