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

Bicarbonate or good old baking soda: Why is this common substance so important in the horse's body? Read on to find out what "bicarb" really does in the horse.

What is bicarbonate:

Bicarbonate is a combination of hydrogen, carbon and three oxygen atoms. Bicarbonate plays a crucial role in maintaining the body's acid-base balance within safe limits, protects the intestines from stomach acid, and is vital in maintaining electrical balance in the horse's body.

What bicarbonate does:

Like many of the other ions we have discussed in previous articles, bicarbonate has an important role in ensuring that body fluids stay within the small safe acid-base (pH) range that is required for a healthy life. Along with chlorine, bicarbonate also provides a negative charge to balance the positive charge of electrolytes like potassium, sodium, and magnesium throughout the body.     

Carbon dioxide is a gas created by body cells when they "burn" oxygen to perform work. High levels of carbon dioxide in an animal's body stops most body functions. Bicarbonate reduces carbon dioxide levels in the body through a complex reaction in the red blood cells.

These amazing cells exchange bicarbonate ions for chloride ions, back and forth, depending if they are "picking up" the carbon dioxide in the muscles (and other organs) or "dropping off" the carbon dioxide in the lungs.

This process quickly transports carbon dioxide to the lungs where it is removed from the body by expiration. This occurs with every breath as oxygen is brought into the body through inspiration and carbon dioxide is excreted from the body through expiration.

The respiratory rate increases rapidly as exercise intensity increases to expel carbon dioxide and replenish the hard-working muscles with oxygen.

Where bicarbonate comes from:

The pancreas and the liver continually secrete bicarbonate into the intestines to neutralise hydrochloric acid from the stomach and optimise absorption of foodstuffs. Bicarbonate is found in forage feedstuffs (hay and chaff) and is often added to concentrate formulations.

Most ingested bicarbonate breaks down into carbon dioxide and water in the highly acidic environment of the stomach.

The carbon dioxide is absorbed into the blood through the intestinal wall and carried back to the lungs to be expelled from the body through expiration as described earlier.

Only a small percentage of ingested bicarbonate is directly absorbed into the blood stream.

Most bicarbonate present in body fluids arises from the interaction between carbon dioxide and water.  The kidney also retains bicarbonate ions and directs them back into the blood stream.

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

Excess bicarbonate will make the fluids in the horse too alkaline. High levels of bicarbonate can cause colic, diarrhoea and lead to depleted levels of other electrolytes such as potassium.

These electrolyte imbalances can lead to muscle spasm, synchronous diaphragmatic flutter (thumps) and cardiac arrhythmias. Changes in mental energy such as depression or agitation may occur in severe imbalances.

Early research showed a decrease in breathing rates in horses after bicarbonate administration. Administration of daily excess bicarbonate over four weeks has been linked to a decrease in aerobic metabolism and an increase in anaerobic metabolism in horses.  Renal retention of bicarbonate ions is reduced if the levels of bicarbonate ions in the blood is too high.

Low levels of bicarbonate can cause the fluids in the horse to become too acidic. As bicarbonate is common in forage this is usually only seen if the horse is not eating as occurs in severe colic, laminitis or neglect.

Behavioural disorders such as crib biting and stall weaving have also been reported for horses with low bicarbonate levels probably due to gastric pain.

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

Feeding your racehorse at least the recommended 1.5% bodyweight of good quality roughage (forage) per day will normally provide sufficient bicarbonate for good health.

Bicarbonate is strictly controlled in the horse's body through a combination of retention in the kidney, manufacture in the pancreas and liver and expiration from the lungs.  Excess bicarbonate is normally only associated with disease of one or more of these organs.  Horse owners and trainers should consult with their veterinarian and/or horse nutritionist if they have concerns about bicarbonate levels in their horses.


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