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In literature on horse nutrition, a great deal is written about the importance of calcium and phosphorus and their relationship between each other. The importance of sodium chloride (NaCl) – “cooking salt”, without which no life would be possible – is often neglected. Not only humans, but also horses need sodium chloride for vital functions.

There is only a small salt content in plants, but in the soil

At the same time, the horse’s natural diet is extremely poor in these minerals. While calcium is found in excess in roughage and phosphorus is abundant in concentrated feed, sodium chloride is hardly available. Especially in regions far from the coast – i.e. about 20 kilometres beyond the sea line – the “salt deficiency area” actually begins. There are many halophytes near the coast – salt-loving plants that absorb the mineral during floods or from the constantly falling sea spray. If horses eat such plants, they get the salt for free. Horses far away in the Alpine region for example, it’s quite a different story. Here, salt has not been present in the plants for millions of years. But in the ground!

Many regions that are now land or even mountains were covered by seas millions of years ago. They dried out with the shifting of the continental plates. Not only fossils were left behind, but also extensive salt crusts. The movement of the earth’s surface caused these dried-up lakes to be torn apart and compressed, soil was pushed over the salt crusts and disappeared underground. Humans discovered such salt deposits early on because wild animals had “salt licks” where the salt could be found just below the earth’s surface. Place names with “Salz” or “Hall” in the name indicate that salt deposits were found here, which humans have been mining and utilising for themselves and their livestock for centuries (https://www.youtube.com/watch?v=uD6GIiqWm3M). Whereas salt used to be worth its weight in gold, modern mining methods have turned it into a mass-produced commodity that is extracted all over the world and marketed cheaply worldwide. From extensive sea salt extraction plants in southern countries to the mining of rock salt in mountainous regions, a whole range of sometimes very exotic salts can now be found on the market.

Salt loss and salt intake must balance each other out

Even our great-grandfathers knew about the importance of salt for their animals. Horses in particular lose sodium chloride through sweating – the reason why sweat tastes “salty”. If the animal sweats profusely on a hot summer’s day, especially when being exercised, it can lose up to 100g of sodium chloride. How much that is, can easily be established with a packet of salt and a kitchen scale: an astonishing amount.

Sport horses in particular lose a lot of salt as they sweat excessively in summer. This salt must be replenished through the feed. It is absorbed in the large intestine and at the same time ensures that the faeces are thickened.

This is because up to the end of the small intestine, the feed bolus is constantly “diluted” by the addition of liquids. The thickening process only begins in the large intestine to prevent diarrhoea. Unfortunately, the body is not able to pump water from one place to another. To do this, it utilises a special property of salt: it is hygroscopic. This means that it attracts water. Anyone who touches the salt lick in the stable can see this: it is always damp, even if no horse has licked it. This is why people used to put grains of rice in the saltshaker, because rice is even more water-attracting than salt: rice kept the salt free-flowing. Thanks to modern “anti-caking agents”, this trick our grandmothers used, is no longer necessary for our table salt.

The property of salt to attract water is utilised in many places in the body. In the large intestine, around 95% of the salt contained in the feed is removed from the feed bolus, and even up to 99% if there is a salt deficiency. This is usually sufficient to simultaneously absorb the water to such an extent that the faeces are thickened to the usual “horse droppings”. If this mechanism does not work, we see this symptomatically as diarrhoea. Prolonged diarrhoea – especially in foals – can lead to considerable salt loss.

Salt regulates the water balance in the body

Salt also fulfils the task of influencing the distribution of water in the body. The body cells of mammals have no solid cell walls, unlike plants. They derive their stability almost exclusively from the internal pressure generated by the cell’s internal fluid. Our cells are therefore comparable to balloons that have been filled with water. They need exactly the right internal water pressure in order to function. If they absorb too much water, they burst. If they absorb too little water, they shrivel and also die. However, the cell cannot pump water directly in or out. It uses salt.

The active absorption of sodium chloride causes water to follow and the cell swells. By actively releasing salt, water flows out of the cell again and the pressure decreases. It is therefore vital for all cells in the organism that exactly the right amount of sodium chloride is always available. Both “too much” and “too little” are life-threatening.

The salt content in the body – as well as the balance of all other minerals – is regulated by the kidneys. They are subject to a complex hormonal (renin-angiotensin-aldosterol) control system, which ensures that they retain sodium chloride in the body or excrete it in the urine as required. Accordingly, a loss of sodium chloride can not only be caused by sweating or diarrhoea, but also by impaired kidney function, in which too much urine is released – something we often observe in horses with insulin resistance (type 2 diabetes).

Salt is much more than just a component of sweat

As well as maintaining internal cell pressure, sodium chloride is also used to retain water in the body as required. This can be seen in “lymphatic” horses. Horses with EMS (Equine Metabolic Syndrome) are often considered as ‘fat’ to the untrained eye.

If you take a closer look, you will see that it is mainly lymphatic deposits that are generally visible in the (hardened, swollen) crest of the mane, sometimes ridges can appear also and in the area of the flanks (“hindquarters”). If the water/salt balance is lasting disturbed, the whole horse can look downright bloated due to excessive lymph deposits in the entire subcutaneous connective tissue.

In such cases, no muscle tone is longer visible, the horse looks like a fully inflated balloon. This condition is currently referred to as pseudo-EMS – as there currently isn’t a better name to describe the complex of symptoms. Pseudo-EMS is always an indication that the metabolism is severely misfunctioning and should therefore be treated with an appropriate therapy, starting at the route course.

fat horse
If the water/salt balance is permanently disturbed, the whole horse can look downright bloated. © Nadine Haase / Adobe Stock

Sodium is also needed together with potassium for nerve transmission and together with chlorine for muscle contraction. It is therefore essential for the functioning of the locomotor system. Sodium is also used by the liver to produce bile, which is essential for a healthy digestive process. Chlorine, on the other hand, is used by the stomach to produce hydrochloric acid (“stomach acid”). Both the sodium from the bile and the chlorine from the stomach acid are largely reabsorbed from the feed bolus in the large intestine.

The key is in the dosage – recognising deficiency and oversupply at the right time

These central key functions show how important sodium chloride is for the body. A lack of sodium chloride often initially causes horses to lick at everything – hands, faces, bars, soil etc. and in severe cases can lead to colic or kidney failure and should therefore not be taken lightly. Lack of appetite, poor performance, poor urination, poor skin turgor (when a fold at the base of the neck is lifted off the body and remains there) and very dry faeces, including a tendency to impaction colic, should also indicate salt deficiency. Conversely, an oversupply of salt often leads to excessive water intake and correspondingly excessive urination and/or diarrhoea, mouth ulcers – especially if salt licks are given in the feed bowl together with the concentrated feed – and mineral imbalance, as in this case too much has to be excreted via the urine, which can also severely disrupt the regulation of other minerals.

Permanent stabled horses in particular often lick the salt lick out of boredom and therefore ingest far too much salt. Attention should be paid to equine-appropriate management instead of simply removing the salt lick.

However, deficiencies in trace elements or microelements (“rare earths”) can also lead to an excessive consumption of the natural salt lick, as other minerals are always present in traces. If the salt stone is “eaten away” after two to three days, it is essential to find the reason for the excessive consumption and treat accordingly. For the body it is essential that there is not too much and not too little available.

Fortunately, the organism normally has a healthy self-regulation in relation to salt intake. Most horse owners know this from themselves: there are phases when you have a real craving for savoury food and add extra salt to every meal. And then there are phases when normally seasoned food seems salty, and the thought of a salty pretzel makes you lose your appetite. Our horses have the same instincts: Most horses regulate their salt requirements perfectly themselves, provided they have the opportunity to do so. Therefore, it has become standard practice in most stables to have salt licks freely available.

Salt licks in all sizes, shapes, and colours

There are different variants on offer. The standard white stones with a hole in the centre are classic. They consist of pressed evaporated salt. This is obtained in mining by dissolving the salt out of the rock using water. This highly saline water (saline) is then boiled away, so to speak, so that salt remains at the end. Although they are made of pure sodium chloride (and, depending on the manufacturer, sometimes contain pressing aids, i.e. adhesives), horses are usually not too keen on these.

Horses are much more likely to take natural salt stones, also known as rock salt or mountain salt. © fotorauschen / Adobe Stock

Horses are much more likely to take natural salt stones, also known as rock salt or mountain salt. They are widely available on the market. Pink-coloured Himalayan salt stones with a hole and string are particularly popular in equestrian retailers. The colour of rock salt differs from white evaporated salt in that it contains traces of other minerals, e.g., calcium, magnesium or iron, which can vary depending on the area of origin. The mining area for the popular Himalayan salt stones is a good distance from the Himalayan mountains in Pakistan. Here, it is mainly extracted by hand from the mountain, cut and tapped to size, drilled and shrink-wrapped in plastic and shipped by container to Europe and elsewhere. The working conditions are rather questionable by our standards: https://www.youtube.com/watch?v=d0NGD0PziOE and the payment of the workers at 3US dollars per tonne of salt extracted (mainly by hand and with dynamite) is probably also rather critical (https://www.youtube.com/watch?v=Pxq2nW0A7gw), especially when compared with the retail prices.

As an alternative, local rock salt was fed to livestock and game long before globalisation. It is still mined today in many places in Germany, Austria, and other European countries (https://www.youtube.com/watch?v=-Fh0SfAEUM8) and varies slightly in colour depending on the mining area, from almost white to grey to pink or rusty red. The working conditions and wages for these salts are more in line with our standards, which generally makes local salt somewhat more expensive. On the other hand, it is not transported halfway around the world, but mined on our own doorstep, so to speak. Just like Himalayan salt, its composition essentially consists of sodium chloride, with some elements that are present in traces and give the salt its particular colour.

Conclusion

As a mental note, in the summertime when horses generally sweat a little more; regardless of the activity: salt should always be offered to horses not only in summer, but all year round, and – with a few exceptions – it should not be administered forced. Reason being is that even on sunny and warm winter days, salt loss through sweating can suddenly increase significantly. Salt lick stones are an excellent way of providing salt and are particularly popular in paddock track systems as an additional ‘Refilling station’ on the track. In summer, a horse normally needs 2-4g Na / 100kg body weight for maintenance. With heavy sweat loss up to 5-10g Na/100kg body weight. Especially with broodmares, attention should be paid that the ‘mother-to-be’ has free access to a salt lick before giving birth, the foal usually doesn’t then experience severe ‘foal heat diarrhoea’. Healthy horses kept in a equine-appropriate management regulate their salt requirements themselves when offered natural salt licks (rock salt or mountain salt). In the event of excessive intake, it is important to find out exactly what the cause is.

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Team Sanoanimal