Electrolytes – The Battery of Life

Electrolytes are minerals existing in the body in an electrically charged, ionized form. Those with positive charges are called cations; negative charges are anions.

     The major electrolyte/free ion circulating in blood (the vascular space) and in the fluid surrounding cells (the extravascular space, i.e. Outside the vascular space) is the cation sodium, symbolized as Na+, followed closely by the anion chloride, Cl-. Next in line, in much smaller amounts, are the cation potassium, K+ and the anion bicarbonate, HCO3-. In addition, phosphate and sulfate groups circulate as anions in low amounts, as do small amounts of free/ionized calcium and magnesium. Inside cells, potassium replaces sodium as the major ion.

A host of essential body functions depend not only on the presence of electrolytes, but also maintenance of precise concentrations of different levels of electrolytes on the inside versus the outside of cells, and even within different sections of a cell. These include:

  • The production and secretion of sweat, saliva, intestinal tract fluids, urine and mucus

  • Heart contraction

  • Intestinal movement (and other involuntary smooth muscle contraction, such as the uterus)

  • Absorption of nutrients across the intestinal wall and into the body cells

  • Skeletal muscle contraction

  • Nerve function

  • Maintenance of normal acid-base balance (pH)

  • Maintenance of normal hydration (the body containing roughly 70% water)

Sweat can  be a major source of electrolyte loss but there are daily losses in urine, manure and mucus that occur all year. Potassium, sodium and chloride are the major electrolytes of concern. Most hays provide potassium concentrations 3 to 4 times higher than need so a horse getting plenty of hay or pasture will not need potassium supplementation unless working very heavily.

Sodium and chloride are another story.  Sodium is the major electrolyte holding water in the body. Levels are very low in the diet. Hay/pasture is the major source of chloride but levels may be borderline and horses not getting generous amounts may be deficient.


Fortunately, there is a simple solution.  Plain salt is sodium chloride. An average size adult horse requires a minimum of 1 ounce of salt per day. Salt is the only mineral for which the horse has a natural “taste”/appetite, but they do not necessarily take in the optimal amount, especially if they have been deprived of adequate salt for an extended period and/or if the only available source is a brick. It’s better to add salt to meals or dissolve and spray on hay. Use coarse, loose salt in a separate small feeder for additional  free choice intake. This is available at livestock supply stores.

Eleanor M Kellon, VMD

About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions, www.drkellon.com, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition.
This entry was posted in Equine Nutrition. Bookmark the permalink.

2 Responses to Electrolytes – The Battery of Life

  1. Billy blackman says:

    If a horse isn’t on an iodine supplement, should the table salt be the kind containing iodine? My horses receive poly copper and poly zinc which I believe contains kelp. Would the kelp be considered an iodine supplement?

    • uckeleequine says:

      To meet the iodine requirement from iodized salt would take about 2 oz/day for the average size adult horse, not harmful but more salt they need at maintenance with cool weather. The polysaccharide in the Poly minerals does come from kelp but iodine dose will depend on how much mineral you need to supplement. It’s easier to use Ocean K.

      Dr. Kellon

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