Integrity Matters' vets continue their look at electrolytes, this time with a focus on potassium.

What is potassium:

Potassium is an essential electrolyte. Most potassium is found in muscles and less than 2% of potassium is found in the body’s fluids.

What potassium does:

Potassium is important in many biochemi­cal reactions in cells, including those essential for nerve and muscle activity. During high-intensity exercise, potas­sium levels in the blood increase as it moves from cells into the bloodstream.

How­ever, within minutes after exercise, the increased blood potassium level returns to normal.

Where potassium comes from:

Grass and hay and many feedstuffs contain high levels of potassium. This means that horses will usually meet their potassium needs through their daily food intake.

The exception to note here is that sweating, heat and humidity increases the horse’s need for potassium. These extra demands can also increase the need for other electrolytes, such as sodium, chloride calcium, and magnesium.

What happens if potassium levels are too high or too low:

Potassium is available in high levels in most forages. Any excess in the diet is excreted through urine, so potassium deficiencies and excesses are rarely a problem in healthy horses.

However, situations of deficiencies of potassium can occur with extreme sweating, as a side effect of diuretics, and occasionally with high grain and low forage diets. Muscle weakness and fatigue can be a result of low levels of potassium intake and a cycle can develop where there is a secondary reduction in appetite and water intake.

Low levels of potassium in horses can also be a cause of nervousness, tying up, muscle fatigue and stiffness.

There is a need for caution when interpreting potassium levels from blood tests. For example, exposure of blood samples to high environmental temperatures, such as may be found if blood samples are stored in a car exposed to direct sunlight, may result in potassium levels in blood increasing after the sample has been collected from the horse. Therefore, high blood potassium levels should first be investigated to see if the sample may have been affected after collection, rather than necessarily as evidence of a medical abnormality.

It is also known that the levels of potassium in blood samples will be lower for several hours after feeding. Therefore, it is recommended that collecting a blood sample to test potassium levels should be avoided for at least three hours after feeding.

How do you ensure your racehorse gets the right amount of potassium:

In most circumstances, a horse’s need for potassium will be met by feeding a low concentrate, high forage diet.

However, as potassium is lost in sweat, a horse’s daily needs can double in heavy work. So, for some horses in heavy work or in hot weather, it may be beneficial for an electrolyte replacement supplement containing potassium to be given. As any excess potassium intake will be excreted from the body in urine, the manufacturer’s recommendations can be followed with confidence.

*Disclaimer: Harness Racing Victoria (HRV) recommends the ingredients of any mineral salt blocks offered should be checked prior to feeding of the horse and if further advice is required, please consult with your local Veterinarian. HRV also recommends that horses should not have unlimited access to mineral salt blocks if the product contains substances such as cobalt.


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