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By Rob Costello, Merrick's Inc, Technical Specialist Bicarbonate has no direct role in acid-base balance. Sodium bicarbonate is an ingredient found in many oral electrolyte solutions. Some calf raisers believe so strongly in its importance that they actually add sodium bicarbonate on the farm to electrolyte formulations that don't provide it. On the other hand, there are studies and articles that demonstrate deleterious effects of sodium bicarbonate and argue the importance of feeding oral electrolyte solutions to calves that do not contain any sodium bicarbonate. So, what's the real story on sodium bicarbonate? The best way to answer this question is to take a look at the role of sodium bicarbonate, or more appropriately, the roles of sodium (Na+) and bicarbonate (HCO3-) in acid-base balance, digestion and rehydration. Keep in mind that when in a liquid, such as water or plasma, sodium bicarbonate (NaHCO3) completely dissociates into Na+ and HCO3-. The same is true of other combinations of ions such as sodium chloride (NaCl). What is the role of bicarbonate in acid-base balance in plasma or any other body fluid? Bicarbonate is the primary transportation form of carbon dioxide in plasma. Its concentration, results from the relationships among independent variables that are directly under the control of the lungs and kidneys. These independent variables, along with hydrogen ion concentration, [H+], determine acid-base balance. HCO3- does not drive or control anything. It is a dependent variable that is basically along for the ride. Historically, HCO3- was important as a calculated value that could be combined with other measures and used to calculate the partial pressure of carbon dioxide in plasma, PCO2, an independent variable with major consequences on acid-base balance. Confusion has therefore arisen as to the role of HCO3-. What is the role of bicarbonate in water absorption from the digestive tract? Bicarbonate has been shown to enhance water absorption at the brush border of the villi in the small intestine. However, when added to a conventional electrolyte solution containing adequate sodium and glucose, bicarbonate has no effect on water absorption. Sodium is the major component of oral electrolyte solutions responsible for water absorption. Glucose enhances sodium absorption, thereby further improving water absorption. What happens to sodium bicarbonate in the digestive tract? Sodium bicarbonate is a simple antacid. As mentioned above, sodium bicarbonate dissociates into Na+ and HCO3- when in liquids. The Na+ component is readily absorbed in the small intestine and does enhance water absorption. However, ingestion of this solution raises the pH in the stomach, making it alkaline instead of acidic. Although this can relieve an upset stomach or heartburn, alkalization of the stomach contents can have some undesirable effects. Presenting an alkaline solution to the small intestine may make the calf more susceptible to pathogens such as E. coli. Beneficial bacteria such as lactobacillus help to protect the small intestine and thrive in lower pH. Increasing intestinal pH compromises these organisms, opening the door to pathogens. In addition, the activity of digestive enzymes can also be affected by pH. An alkaline environment in the upper GI tract can interfere with nutrient digestion and absorption. Research has shown that feeding oral electrolyte solutions containing bicarbonate to scouring calves not only interferes with digestion, but it also has a deleterious effect on body weight. This effect is more pronounced when milk feeding is continued throughout rehydration therapy. However, milk/milk replacer fed calves maintain or improve body weight during scours, while withholding these nutrients results in weight loss. Due to the beneficial effects on weight and overall health status, maintaining normal nutrient intake during scours and rehydration therapy is the recommended practice. Increasing bicarbonate in the digestive tract through oral supplementation would not be expected to have a significant, consistent effect on its absorption or on plasma [HCO3-]. Oral supplementation of bicarbonate in healthy subjects undergoing extensive lactic acid production in muscle tissue has been the subject of recent research and debate. Bicarbonate doping, or consumption of large amounts of bicarbonate prior to a race event, has been used in both horse and bicycle racing in an attempt to provide a competitive advantage during intense, strenuous exercise when lactic acid is being produced in the body. Results have been mixed and inconsistent. In calves that have lost their suckling reflex and have acidemia, there is evidence that force feeding an electrolyte solution with bicarbonate can reduce acidemia. However, calves that have lost their suckling reflex are poor candidates for oral rehydration therapy. Recumbent, acidotic calves usually require immediate, invasive treatment just to keep them alive. The primary objectives of administering an oral electrolyte solution are to maximize water absorption from the digestive tract and to facilitate the rapid reestablishment of water balance between the plasma and cells within the animal's body. As far as sodium bicarbonate goes, there are few instances where its inclusion in an oral electrolyte solution results in a beneficial effect. In fact, most of the effects of added bicarbonate in the digestive tract are negative ones.  
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