Studies on the effects of alkalizing agents on acid-base balance in horses

Alkalizing agents have been used prior to competition in the Standardbred Racing Industry to improve performance. The physiological response of horses administered alkalizing agents is increased blood pH and bicarbonate ion concentration. In human subjects, an ergogenic effect has been found after ingestion of alkalizing agents. The underlying mechanism accepted by most authors is that enhancing the blood buffering capacity will augment the efflux of lactic acid out of working muscle and delay the onset of fatigue. Significant improvement in performance has not been demonstrated in horses after ingestion alkalizing agents and only circumstantial evidence exists. The practice of administering alkalyzing agents to horns before racing is otherwise known as "milkshaking". Regulations now exist to prevent this illegal pre-race procedure by pre-race quarantine and determination of blood pH, bicarbonate ion concentration and other blood gas indices. Our group studied the effects of sodium bicarbonate and other weak acid salts on the acid-base balance of horses. It was found that sodium bicarbonate increased pH and blood bicarbonate ion concentration within one hour after incubation and the other treatments produced a delayed alkalyzing effect. We determined that a longer quarantine period may be needed in order to prevent the use of sodium acetate, sodium citrate and sodium phosphate. We also investigated the changes in acid-base balance due to intravenous administration of sodium bicarbonate, sodium acetate, and other commercially available intravenous preparations. Results indicated that sodium bicarbonate and sodium acetate increased (P < 0.0001) blood pH and bicarbonate ion concentration after infusion. It was suggested that pre-race quarantine is necessary to prevent this type of administration. Furthermore, we examined the effects of sodium bicarbonate, sodium acetate, sodium phosphate and two bouts of exercise on acid-base balance. We found that horses treated with sodium bicarbonate and sodium acetate had higher blood pH and bicarbonate concentrations. Sodium phosphate did not elevate blood pH or bicarbonate ion concentration. It was suggested that the alkalizing agents studied have different physiological mechanisms which are responsible for producing an increased bicarbonate ion concentration.