How much salt does your horse need?
Danielle Nielsen | 27.02.21
What is the importance of salt in the horse’s body?
An average 500kg horse requires 10 grams of sodium and 40 grams of chloride per day when conditions are cool, and the horse is not working (NRC, 2007). When work increases to a moderate level, requirements also increase to 17.8 grams and 53.3 grams respectively and this does not account for hot weather. These two electrolytes are critical to the function of numerous cellular processes within your horse’s body and for that matter, yours as well!
Salt is important because it is made up of Sodium and Chloride – two electrolytes (charged ions) which play a major role in cell function. Sodium (positively charged) and chloride (negatively charged) are major components of the fluid surrounding our cells (extracellular fluid) and inside our cells (intracellular fluid). Along with potassium (positively charged), these electrolytes create a concentration gradient across the cell membrane which allows them to determine acid base balance and fluid regulation of the cells.
Sodium plays a vital role in the functioning of the central nervous system. When nerves are triggered, channels in the nerve cell membranes open and the sodium ions move into the cell. This changes the internal electronic charge of the cell from negative to positive. Gradually potassium channels open and the process is reversed. Tightly controlling the concentration gradient across cell membranes is vital for nerve cell function and therefore electrolyte levels are vital to nerve conduction. This tightly controlled concentration gradient is also essential for muscle contract. Therefore, a horse with inadequate sodium/chloride status may have compromised nervous and muscular skeletal performance.
Sodium also plays a role in maintaining hydration. There are sensors in the brain that monitor circulating sodium concentration. If sodium in the blood becomes too high a thirst response is triggered motivating consumption of water. This means that additional sodium encourages water consumption which is important as water is vital for numerous bodily functions.
Chloride is an essential component of bile as well as hydrochloric acid, a major secretion in the stomach necessary for digestion.
What happens if your horse is not getting enough sodium or chloride?
As discussed, Sodium and Chloride play major roles in bodily functions. For this reason, the body has several mechanisms in place to control concentrations.
The kidney’s control excretion in response to signals from around the body. When circulating sodium levels are low, less sodium is excreted in urine. Instead, the kidneys will excrete more potassium to try and maintain correct electrolyte balance. Sodium attracts water, meaning urine with lower sodium content will contain less water and be more concentrated. Ironically, lower circulating sodium means less thirst stimulus so while water is conserved by reducing excretion, consumption of more water is not stimulated and as a result dehydration may occur.
Despite the horse’s ability to adapt well to reduced sodium intake thanks to the various regulatory mechanisms, horses that are not consuming adequate sodium will have low-level dehydration which may become an issue should greater demands be placed on them. Horses consuming inadequate amounts of sodium are more likely to suffer from heat stress, and electrolyte imbalances than those consuming the correct daily intake of sodium and chloride. They may also have an increased risk of impaction colic due to reduced fluid consumption and flow through the gastrointestinal tract. The saltiness of blood can also influence sweating. When the horse becomes dehydrated and the blood sodium level is much more concentrated, sweating will slow or even stop as the body is trying to preserve the critical balance of salt to water. However, without adequate sweating, dangerous overheating can result.
Symptoms associated with inadequate sodium and chloride intake include:
- Electrolyte imbalance
- Increased risk of impaction colic
- Decreased feed intake
- Weight loss
- Muscle weakness
- Decreased milk production
- Decreased skin turgor (skin stays tented when pinched)
- Licking objects
- Uncoordinated muscle contractions
How do I ensure my horse is receiving adequate daily intake of sodium and chloride?
Sodium and chloride levels in forages vary and without a forage analysis it should not be assumed that they are adequate to meet daily requirements. While sodium and chloride are both added to commercial feeds to help meet requirements and aid in palatability the amounts may not be enough to meet daily needs especially in working horses. Therefore, the best practice is to insure a supplemental source.
Regular table salt, sodium chloride, is approximately 61% chloride and 39% sodium. Feeding 30 grams of salt a day will provide 18.3 grams of chloride and 11.7 grams of sodium, enough to meet the maintenance needs of a 500 kg horse.
Be sure to use sodium chloride not lite salt as the latter is potassium chloride and will not help maintain sodium levels. There is no added nutritional benefit of more gourmet forms of salt, Himalayan, or sea salt.
Can I feed too much salt?
As for whether you can give too much salt the National Research Council advises that as long as adequate water is available excess sodium will be excreted in urine and gives the maximum tolerable concentration in the ration of 6% of total feed intake. Research suggests that large intakes of salt may lead to gastric ulceration however the levels of salt administered in the study were significantly greater than would reasonably be given. Keep in mind that the purpose of giving salt is to provide adequate sodium and chloride to meet daily maintenance requirements not to replace sweat losses. Horses can lose large quantities of sodium and chloride in sweat and for these replacement purposes additional salt is required. Providing your horse with adequate salt each day can go a long way in maintaining hydration which not only safeguards health but supports optimal performance.
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