Bicarbonate loading in the Thoroughbred: Dose, method of administration and acid‐base changes

Summary Two studies were undertaken in an attempt to investigate the optimal dose, route and time course required to ‘bicarbonate load’ the Thoroughbred. During the first study a test solution of sodium bicarbonate (NaHCO 3 ) and a control solution of water were administered via a nasogastric tube to six horses. Blood acid‐base status was determined immediately prior to and for 24 h following intubation. During the second study a standardised feed was given to four horses, with and without NaHCO 3 supplementation. This was followed by a further trial involving the addition of glucose and NaHCO 3 to a standardised feed. During Study 1, plasma pH peaked 8 h after NaHCO 3 intubation (7.433 ± 0.020) and levels were still elevated above control values 12 h post intubation. Although there was a trend for blood PCO 2 to be elevated above control values at all times after NaHCO 3 administration, values were only significantly different at 4 and 5 h post intubation. The patterns of change in plasma HCO 3 − and blood base‐excess after NaHCO 3 administration were similar. Values peaked between 3 and 6 h post intubation and were still above control values 12 h post intubation. In Study 2 attempts to alter acid‐base status by presenting NaHCO 3 mixed with feed were unsuccessful because horses failed to consume the total mix, despite attempts to mask the unpalatable nature of the feed by adding glucose. The results suggest that future studies investigating the influence of NaHCO 3 on exercise performance and metabolism should possibly involve administration of NaHCO 3 in a greater quantity than is administered conventionally (0.3g/kg). More meaningful results may be obtained if NaHCO 3 is administered as a solution, via a nasogastric tube, at least 3 h prior to exercis