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Electrolytes and Minerals in Horses

What do the individual electrolytes and trace minerals do in horses?

Sodium is the main and most important electrolyte in the ECF, or extra cellular fluid. ECF means the fluid outside of the cells, as opposed to inside the cells. Salt (sodium chloride) has been valuable to mankind for centuries. The Romans paid soldiers in salt, thus the modern term, “salary”. The majority of plants, a horse’s main source of feeds, do not provide sufficient sodium (or chloride) to meet the horse’s requirements. Horses therefore have a definite appetite for salt; they’re always on the lookout for a good source!

In young horses sodium deficiency can lead to reduced growth rate, depressed immune system and poor feed efficiency. Adult horses are most likely to show signs of sodium deficiency when working hard in hot weather. Salt-deficient horses tire easily, show muscle tremors, hemoconcentration (blood that’s low in water), acidosis (acidic blood, reduces endurance), and may stop sweating. Let’s look at the physiology of that one: the horse detects low electrolyte levels in the body fluids. In the attempt to conserve the fluid, losses are reduced, and stopping sweating is one way to reduce loss of sweat (consisting of both water and electrolytes). Unfortunately that’s also a good way to get hyper thermic (overheated). In lactating mares, a sodium deficiency seriously reduces milk production. Physiologically, that makes sense: conserving the fluids.

Potassium is the main intracellular fluid electrolyte inside the cells. It works closely with sodium in maintaining cell volume and electrical properties. Potassium is very important in keeping muscles and nerves functioning properly. The horse’s body tries to maintain a specific ration or gradient of potassium inside the cells and sodium outside the cells. A horse that’s very low in potassium due to sweating may be weak, with muscle tremors and even heart arrhythmias. A standardbred during a race loses about 10 grams of potassium, while a Thoroughbred workout loses about 7 grams and an 85 km endurance ride horse will lose about 30 grams potassium.

Calcium is famous for its benefits in promoting healthy bones and teeth, but it also works with vitamin D. The calcium: phosphorus ratio is worth exploring too; grasses contain low levels of both, but cereal grains are high in phosphorus but low in calcium. Calcium is also important for muscle contraction, by activating potassium ion channels in the membrane of the muscle cells. Additionally, calcium regulates enzymes, which assist in the breakdown of larger molecules.

Magnesium is important for nerves and muscle, and a horse with a magnesium deficiency may be nervous and excitable, with muscle tremors and a propensity to tie up. As such, supplementing magnesium may help promote healthy nerve function. Care should be taken to avoid over-supplementing magnesium only.

Iron is well known to be required for red blood cell production. Iron is at the center of every hemoglobin molecule. While it is rare for a horse to be iron deficient due to dietary problems, iron deficiency can be caused by chronic blood loss (by a gastric ulcer, for example) or due to parasites.

Zinc deficiency in foals may cause reduced growth rates in skin, hoof and coat problems.

Copper is important in the creation of connective and other tissue structures. For example, copper deficiency is associated with uterine artery rupture in older mares, aortic aneurysms, contracted tendons and improper cartilage formation in foals.

Cobalt is the heart of the Vitamin B12 molecule, just like Iron it is at the heart of the hemoglobin molecule. Horses need low levels of cobalt to help synthesize vitamin B12.

Manganese deficiency is associated with bone structure problems. Chondroitin sulfate can’t be synthesized by the horse’s body without it; that’s why manganese is present in many joint supplements. Manganese is also important for several enzymes systems such as manganese superoxide dismutase.