The effect of oral sodium acetate administration on plasma acetate concentration and acid-base state in horses

Abstract

Aim: Sodium acetate (NaAcetate) has received some attention as an alkalinizing agent and possible alternative energy source for the horse, however the effects of oral administration remain largely unknown. The present study used the physicochemical approach to characterize the changes in acid-base status occurring after oral NaAcetate/acetic acid (NAA) administration in horses.

Methods: Jugular venous blood was sampled from 9 exercise-conditioned horses on 2 separate occasions, at rest and for 24 h following a competition exercise test (CET) designed to simulate the speed and endurance test of 3-day event. Immediately after the CETs horses were allowed water ad libitum and either: 1) 8 L of a hypertonic NaAcetate/acetic acid solution via nasogastric tube followed by a typical hay/grain meal (NAA trial); or 2) a hay/grain meal alone (Control trial).

Results: Oral NAA resulted in a profound plasma alkalosis marked by decreased plasma [H+] and increased plasma [TCO2] and [HCO3-] compared to Control. The primary contributor to the plasma alkalosis was an increased [SID], as a result of increased plasma [Na+] and decreased plasma [Cl-]. An increased [Atot], due to increased [PP] and a sustained increase in plasma [acetate], contributed a minor acidifying effect.

Conclusion: It is concluded that oral NaAcetate could be used as both an alkalinizing agent and an alternative energy source in the horse.

Figure 1

Linear regression relationship (solid lines) and 95% confidence interval (dashed lines) between measured and calculated plasma [H⁺] in 9 horses before and after a Competition Exercise Test. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Provide the equation with the p value SEE = standard error of the estimate.

Figure 2

The time course of plasma electrolyte concentrations: (A) sodium (Na⁺), (B) potassium (K⁺), (C) chloride (Cl^-) and (D) calcium (Ca²⁺) after a Competition Exercise Test. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. *, Ψ: significantly different from baseline (pre-exercise) time point for Control and NAA trials, respectively.

Figure 3

The time course of plasma acetate concentration after a Competition Exercise Test. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. *, Ψ: significantly different from baseline (pre-exercise) time point for Control and NAA trials, respectively.

Figure 4

The time course of the independent acid-base variables in plasma: (A) strong ion difference ([SID]), (B) partial pressure of carbon dioxide (PCO₂), and (C) total weak acid concentration ([A_tot]), after a Competition Exercise Test. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. *, Ψ: significantly different from baseline (pre-exercise) time point for Control and NAA trials, respectively.

Figure 5

The time course of the dependent acid-base variable plasma hydrogen ion concentration ([H⁺]) after a Competition Exercise Test, and the contributions of the independent variables ([SID], solid square), total weak acid concentration ([A_tot], hollow circle) or partial pressure of carbon dioxide (PCO₂, solid triangle) to the change in plasma [H⁺], for (B) the NAA trial and (C) the Control trial. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. *, Ψ: significantly different from baseline (pre-exercise) time point for Control and NAA trials, respectively.

Figure 6

The time course of the plasma total carbon dioxide concentration ([TCO₂]) after a Competition Exercise Test, and the contributions of the independent variables ([SID], solid square), total weak acid concentration ([A_tot], hollow circle) or partial pressure of carbon dioxide (PCO₂, solid triangle) to the change in [TCO₂], for (B) the NAA trial and (C) the Control trial. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. *, Ψ: significantly different from baseline (pre-exercise) time point for Control and NAA trials, respectively.

Figure 7

The time course of the changes in plasma osmolality, after a Competition Exercise Test. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. *, Ψ: significantly different from baseline (pre-exercise) time point for Control and NAA trials, respectively.

Figure 8

The time course of cumulative water consumption, after a Competition Exercise Test. The exercise recovery period begins at 0 min, after horses were either given a hypertonic sodium acetate/acetic acid solution (NAA trial; solid square), or stood in stocks (Control trial; hollow circle). Horses were fed immediately after the 0 and 360 min samples. Values are mean ± SE for 9 horses. * = significantly different from the Control trial.