DETECTION OF BICARBONATE ADMINISTRATION (MILKSHAKE) IN STANDARD-BRED HORSES

Total plasma carbon dioxide (TCO2) concentrations were measured in Sta ndard bred horses to determine criteria to discriminate between normal horses and horses with excessive TCO2 concentrations on raceday. TCO2 concentrations from stabled horses were distributed normally with a m ean of 30.2 mmol/L and a standard deviation of 1.2 (n = 192) while pre -race TCO2 concentrations were not normally distributed. The results i ndicate that about 50 horses per million are likely to have TCO2 conce ntrations greater than or equal to 35 mmol/L and that it is extremely unlikely that a normal horse would have a resting TCO2 concentration a bove 36 mmol/L. These values were associated with sensitivities of 67% and 59%, respectively, and with a specificity of 100%. TCO2 concentra tions were relatively stable in blood samples stored at 4-degrees-C fo r 4 days, whereas the TCO2 in specimens stored at room temperature (25 -degrees-C) and at ambient temperature (16-28-degrees-C) declined prog ressively over 5 days. The accuracy and precision of the Beckman EL-IS E Auto Analyser were acceptable and within the manufacturers specified range. Paired specimens analysed using a Beckman EL-ISE Auto Analyser and a Kodak Dry Chemistry Analyser were not significantly different. However, the measurements made using the Kodak Dry Chemistry Analyser averaged 0.5 mmol/L higher than those analysed on the Beckman EL-ISE. The significance of these sources of variation in TCO2 concentration i n relation to the testing of horses for 'milkshake' administration are discussed.