Salt, or sodium chloride, is a necessary component of a horse’s diet and metabolism. However; too much salt will increase thirst and urination. Hoof quality can deteriorate from the additional urine and moisture in the environment. Horses that are confined for periods of time are primarily affected.

The excess moisture softens the hoof wall and sole leading to weakening, wall separations and cracks. The sole swells, the white line widens, and the softer hoof wall bends outward. This has the adverse effect of shifting and increasing weight bearing on the sole rather than the hoof wall. Hoof eating microbes also have increased opportunity for invasion. These softened structures are more likely to be ground and abraded away from exercise or stall boredom.

To add further insult, urine soaked bedding has been associated with higher ammonia levels. Ammonia is not only damaging to the horse’s respiratory system but is very destructive to the hooves. Urine contains a breakdown product of protein metabolism called urea. Urea is converted to ammonia by microbial activity in the bedding. Although salt intake would not affect the total daily urea output from a horse, the additional moisture from increased urine output facilitates the bacterial production of the enzyme that breaks down urea into ammonia (urease).

The horse’s salt requirement varies between horses depending on several factors including activity level and amount of sweating. The maintenance requirement of an 1100 lb. horse at rest is approximately 25 grams per day. On the other hand, the horse in heavy work may require up to 200 grams of salt. Fortunately, by offering salt free choice, the vast majority of horses voluntarily consume only the amount of salt that they require.

Unlike the rough tongue of a cow, the smooth tongue of the horse is inefficient at removing salt from blocks designed to withstand the weather. They will often bite off large chunks of a salt block resulting in excess intake. Free choice loose white salt, or often called livestock feeding salt, is the best option.

Compounded feeds usually contain added salt at 0.5% to 1.0 %. Salt in the ration increases the palatability of the feed. Hard keepers that need large feeding levels of a compounded feed in order to maintain his/her weight can consume significant levels of salt in the feed. For example over the course of a day the hard keeper horse fed 12 pounds of compounded feed with 1% added salt would be consuming 55 grams of salt. The horse that is not working or sweating is being force fed more than twice the requirement. A better option for hard keepers would be feeding a low salt feed such as a forage balancer and a non-fortified calorie source such as whole oats. Add free-choice loose white salt and fresh water for a balanced diet.

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Scott Gravlee, DVM, CNS 
Equine Nutrition Consultant
Life Data Labs, Inc.
Maker's of Farrier's Formula^®