Feed your Horse Salt

for your horse’s well being and prevent fatigue. There are many body processes that require electrolytes plus a lot is lost in sweat.

The reason why it is so important to feed salt is that salt is made up of sodium and chloride (NaCl). These key electrolytes are often too low in horses’ intakes. This is true for cold climates and even more likely in a hot climate or use rugs or do a lot of floating (transporting) of horses; horses need salt supplementation as so much can be lost in sweat.

The key electrolytes include sodium, chloride and potassium. Grass/hay and other feeds are relatively high in potassium for horses which is fantastic as it means you generally don’t need to supplement potassium, unless the horse has no access to feed for a period of time and is sweating.

Horses need electrolytes for daily body maintenance jobs (staying alive) and to replace what is lost in sweat. Some of the important jobs include:

The production and secretion of sweat, saliva, intestinal tract fluids, urine and mucus
Skeletal muscle contraction
Heart contraction
Nerve function
Intestinal movement (and other involuntary smooth muscle contraction, such as the uterus)
Absorption of nutrients across the intestinal wall and into the body cells
Maintenance of normal acid-base balance (pH)
Maintenance of normal hydration (the body contains roughly 70% water)
Preventing tying up
Preventing fatigue

How to supplement salt

Providing a salt lick or better, a bucket of loose salt is an excellent strategy in addition to feeding salt, but on it’s own, can’t be relied on to cover maintenance and sweat requirements. Despite salt being the only documented craving horses have, some horses won’t touch a salt lick or not access it enough. Don’t rely on free choice salt intake unless you can accurately measure what each horse is taking in. Adding salt to a feed will go a long way to ensure a horse will have the sodium and chloride needs covered with forage and feeds as the potassium source. For an untested situation, Dr Kellon recommends around 2 metric tablespoons of salt in a feed, and more per day for horses in hot climates. If you plan to introduce feeding salt, start with a very small amount and build up gradually to allow time for the horse to adjust to the change in flavour.

If possible, mix the salt in with the soak water in your choice of bagged feed/chaff you put in the feed bucket. Ideally your chosen feed is a high fibre feed (beet pulp, soybean hulls and/or lupin hulls) rather than low fibre/high starch/grain feed.

This video shows one approach for adding salt (and minerals). The salt will become sodium and chloride ions in the soak water. Whatever your choice of feed, it should be fed wet to prevent choke and reduce dust.

Which salt?

Best salt to use is plain salt or iodised salt if your horse needs more iodine. If the salt is pink or what is known by many nutritionists as ‘dirty salt’ then you are probably paying a premium for a salt product that contains microscopic traces of minerals and heavy metals. The amount of minerals in these products are so tiny it’s not worth counting towards satisfying daily requirements.

Salt can be purchased cheaply in bulk in 20 or 25 kg bags from many stockfeed suppliers.

Quirky behaviours

One horse owner who contacted me wondered why his horse always licked the ground in the same spot when out on a trail ride. On adding 2 tablespoons of salt to his horse’s feed (per day) he found his horse no longer wanted to lick the ground. He observed his horse drinking more water and looking more hydrated.

Over the years I’ve been asked about this with similar stories. There may be a particular spot in the paddock or out on the trail or a propensity for eating dirt or manure. Whilst a salt craving may not be the only possible answer, it’s easy to experiment to see if the behaviour continues after feeding salt.

One theory that explains why horses have such a relatively high need for salt is that they evolved in a region of North America with very saline soils.

What about potassium?

Is potassium harmful in excess – NO unless in exceptional circumstances due to say poor choices with fertilising pasture results in >4% DM on the pasture test OR the horse has a veterinary issue such as Hyperkalemic Periodic Paralysis (HYPP), an inherited condition.

All forages; grass and hay are a rich source of potassium so it doesn’t need to be supplemented for a horse that is not in work. Access to food means the horse will be getting a lot of potassium. Any electrolyte excess is easily and efficiently excreted from the kidneys in the urine. Of course, drinking water should always be provided. This is normal for horses, does no harm. The excess can be removed as quickly as within an hour.

Timing of feeding salt

If you feed more than once per day, spread out the daily amount among those feeds since horses can’t ‘stockpile’ electrolytes.

Can sodium or chloride deficiency be harmful – Yes.

Electrolytes in the body

If your horse often seems tired or flat/ little energy, one possible reason is a lack of salt in the intake as insufficient sodium is related to dehydration.

Precise electrolyte concentrations are maintained in and out of cells and in certain parts of cells. The movement of electrolytes in and out of cells is what enables nutrients to move from one place to another. Electrolytes are vital for the function of the nervous system and skeletal muscle and to prevent tying up. Electrolyte supplementation even enhances muscle glycogen repletion which means your horse is more likely to have energy stores replenished for the next workout. Dr Eleanor Kellon VMD, a leader in equine nutrition reports that as little as 2 to 3% dehydration can lead to a 10% drop in performance.

Electrolyte levels in the blood are tightly regulated by hormones. This is of paramount importance so other areas of the body will go without to ensure the bloodstream maintains a narrow range of concentration. If sodium is low, the body will draw the sodium ions from the extracellular spaces (between cells) and results in the horse’s skin getting that dehydrated, tented look. When a vet pinches the skin near the shoulder they are getting a measure of skin elasticity, an indication of sodium deficiency.

There is some evidence that the sodium in sodium chloride can increase absorption of other ionised minerals. Sodium appears to increase permeability of the lining. For example, in the case of phosphorus (and glucose) there is a cotransporter that absorbs them together.

Working on a hot day - sweat

Sodium is also the major controller of water balance in tissues. Sodium levels in the brain are read by cells called osmoreceptors, short for osmolality. In addition to ‘holding’ water in the tissues, sodium is what the brain ‘reads’ in determining when to trigger thirst and when to regulate the amount of sodium and water the body excretes in the urine.

Chloride is involved in a host of reactions that include maintaining normal pH, fluid volume and electrical conductivity of cells.

All forages; grass and hay are a rich source of potassium so it doesn’t need to be supplemented for a horse that is not in work. Sodium though is rarely in sufficient quantities to satisfy maintenance needs unless the soil the pasture is grown on is quite saline. Adding 2 metric tablespoons of salt (sodium chloride) per feed to a horse’s feed is a reasonable amount to cover maintenance electrolyte requirements, especially for a horse that sweats on a hot day standing around in a paddock or on a short trail ride. Any excess is easily and efficiently excreted from the kidneys. Of course, drinking water should always be provided.

Potassium is the major electrolyte inside a cell; the difference in sodium and potassium concentrations outside and inside cells is responsible for excitability of muscle and nerve tissue. If potassium is deficient symptoms can include fatigue, heart rhythm irregularities, muscle weakness or tying up (Rhabdomyolysis) and nerve irritability, also known as ‘Thumps’.

For example, the National Research Council (NRC), in the current 6th revised edition of Nutrient Requirements of Horses (2007) gives the following calculations to determine maintenance requirements based on body weight (BW). For sodium it is 0.02 x BW and chloride, 0.08 x BW. A 450 kg horse requires 9 grams of sodium and 36 grams chloride per day. These are minimum levels; it doesn’t take into account sweat losses on a hot day or exercise. A level tablespoon of salt contains approximately 9 grams of sodium and 14 grams of chloride.

If a horse is exercised for more than 2 hours then an electrolyte mix with potassium is necessary to replace heavy losses in sweat. Electrolytes can be added directly to a feed or syringed. If syringing, mix with a little sugar, preferably glucose. Sodium, chloride and potassium move through the intestinal wall into the bloodstream via passive transport; the ions fit through the small holes or pores. However, a small amount of sugar or amino acids (protein) will enable active transport of sodium, a quicker process than passive transport. This applies only to sodium, not chloride or potassium.

You might see your horse foaming if heavily sweating during exercise. Read about latherin in foam.

Article originally published in the November – December 2009 issue of Equine Excellence magazine with the title of ‘The importance of electrolytes’, updated since.

Salt; plain or iodised

Working on a hot day - sweat

Feed your Horse Salt

How to supplement salt

Which salt?

Quirky behaviours

What about potassium?

Timing of feeding salt

Electrolytes in the body

Further reading:

Salt; plain or iodised

Working on a hot day - sweat