Salt is the most important mineral required by horses, yet its importance is often overlooked in favour of seemingly more important minerals.
Although the majority of a horse’s mineral quota will be met with a good-quality long-stem forage, the salt content in grasses and hay is too low for the needs of a horse. Consequently all horses will need salt supplementation. Salt is an essential part of nutrition and just like any other nutritional deficiency, when a horse’s salt requirement is not met health consequences develop over time.
Common salt, a combination of sodium and chloride, is essential for countless critical functions in the body. When dissolved in the bloodstream these two minerals become ionized and are integral to electrical signals and communication throughout the body. This communication is instrumental for the nervous and musculoskeletal systems to function properly.
Sodium has the ability to hold water in the tissues and thus its presence has a major influence on hydration and fluid dynamics in the body. Insufficient sodium inevitably leads to a degree of dehydration. This function of sodium is so important to the body that the sodium levels are “read” by the brain in determining when to trigger thirst.
Sodium is also involved in moving glucose across the cell membrane where it is used as a fuel source. If sodium is insufficient at the cellular level glucose transport in the tissues is impaired. Ultimately this translates into ill health and may present as early fatigue, muscle weaknesses and impaired performance. Less recognized benefits of adequate salt are an aid in blood sugar regulation, hormone balance, maintenance of healthy weight, health of hooves and hair coat, pH balance of the body and its function as a natural antihistamine.
Salt insufficiency generally develops over a period of weeks or months and clinical signs of minor deficiencies are generally non-specific and subtle. Fortunately the behaviour of the horses themselves provides a valuable clue regarding their salt requirement. Horses lacking salt often develop an abnormal appetite, also known as “pica” and lick objects that may have traces of salt on them. These can include but are not limited to wood, metal, stones, fences, bark, hands, vehicles, and soil. Although the occurrence of pica does not necessarily indicate a salt deficiency, it does warrant a check for the availability of a sufficient salt source. A decrease in water intake often accompanies a salt deficiency as the body attempts to preserve what salt it does have. The dehydration closely associated with salt deficiency places such horses at a greater risk for colic.
Salt requirement of any one individual horse is in a constant state of flux — just observe the daily activity around the salt lick within a group of horses for a period of time. This is because “true” salt intake is influenced by a number of factors including an animal’s own unique biochemistry, diet, lifestyle and various events in the horse’s life. Even the weather will determine the amount of salt a horse needs, since weather directly affects the growth and chemical composition of forages. The salinity of water sources can also influence a horse’s need for salt from outside sources. Waters from deep ground wells tend to be quite saline in nature.
With so many variables influencing the salt needs of a horse, it becomes problematic for human logic to determine the exactness of any one horse’s salt requirements. Fortunately horses have an innate ability or inner wisdom to regulate their own salt requirement. Therefore it is possible to allow the horse itself to meet its own salt equilibrium. In order to do so it will need free-choice access to a readily available source of salt.
First, some basics: an average-size horse of 450 kg (1,000 pounds) needs roughly two level tablespoons or one ounce of salt per day to meet its requirement for sodium and chloride. The demand for salt will flux daily and can double and even triple when workload and/or hot and humid environments increase sweat losses.
Providing salt for horses can mean simply tossing out a salt block. As convenient and economical as this common practice is, it does have shortcomings and often does not suffice meeting the salt requirements of many horses.
Processed and/or pressed salt blocks were originally designed to be consumed by the rough tongue of cattle, and so the smooth tongue of the horse often fails to easily remove the quantity of salt necessary to satiate the horse. While the addition of trace minerals in “colour-coded” salt blocks may seem to be a good idea, the inexpensive forms of inorganic minerals used are rarely bioavailable to the animal. Some horses object to the bitter taste of minerals in the salt block and thus will not ingest the salt they require.
One way to improve availability of salt for the horse is to provide a source of natural salt. It has been my experience that horses offered a source of natural salt will increase their consumption of salt, considerably so at times. Natural salts are not pure white in colour, rather they are reddish, pink or grey due to their unrefined mineral content. They can be purchased as uneven “rocks” or licks. The fissures and variations in densities and textures inherent to the mined “rocks” create a “softer” lick for the horse, thus increasing their availability for salt.
Providing horses with a loose granular or free-flowing form of salt has also been shown to increase both their salt and water consumption. In order to minimize wastage while providing this form of salt it is necessary to utilize covered mineral feeders or secure buckets with the loose granulated salt in protected shelters.
Horses appear to have an innate intelligence when meeting their salt requirements and they also appear to have a preference regarding the quality of salt offered to them. Whenever the salt source is well received by the horse the horse’s own intake will naturally wax and wane as it is continually meeting its own salt equilibrium.