Technical note: Using calcium carbonate as an osmolar control treatment for acid-base studies in horses

The efficacy of using calcium carbonate as an osmolar control treatment for acid-base studies in horses receiving alkalizing compounds was evaluated. Six mares were nasogastrically intubated with isomolar quantities of sodium :or calcium as sodium bicarbonate or calcium carbonate or with water during three treatment periods. Doses of the carbonic acid salts were 500 mg/kg s odium bicarbonate mixed with 4 L of distilled water (positive control) and 595 mg/kg calcium carbonate mixed with 2 L of distilled water to yield isoo smolar treatments. Four liters of distilled water served as the negative co ntrol. Jugular venous blood samples were drawn before intubation and at hou rly intervals for 6 h after intubation. The serum electrolytes Na+ and K+, blood pH, and KCO3- were determined. The sodium bicarbonate treatment incre ased blood pH and HCO3- (P < 0.01) above both the water and CaCO3 treatment s. Nd differences (P >0.05) were found between the water and CaCO3 treatmen ts. These data indicate that calcium carbonate may serve as a suitable osmo lar control treatment for studying the effects of treatments that affect ac id-base status of horses.