When Apple-A-Day was formulated, sodium bicarbonate was included for two very important reasons:

1. Finish Line wanted a source of sodium, in addition to the sodium chloride, that did not additionally raise the chloride concentration, since the chloride level is from both sodium chloride plus potassium chloride. Finish Line has always paid close attention to the ratios of salt components to each other.
2. The belief at that time (1983) was that bicarbonate would help buffer the rising lactic acid during physical exertion, thus allowing some extra time before fatigue set in. This theory went out of favor for a few years but it is now clearly back in fashion as evidenced by recent literature1, and by the very existence of the "Milkshake".

A one volume ounce scoop of Apple-A-Day weighs 38 grams, which is a testament to its high density of electrolytes/minerals. There are no fillers like sugars in Apple-A-Day. Consider, also, that sodium bicarbonate raw material costs 12 times more than sodium chloride raw material! It's there for good reason. Of that 38 gram serving, about 7 grams of it is sodium bicarbonate. Therefore, on a typical daily basis for a working horse in hot weather, he/she would get about 14 grams sodium bicarbonate per day from 2 scoops of Apple-A-Day. Compare that to the quantity used in a research study1, of 300mg/kg body weight, or 150 grams for a 500kg horse. Apple-A-Day contains ten times LESS bicarbonate than used in the research study. Apple-A-Day may contain even less bicarbonate relative to some actual "Milkshake" formulas.

The Bottom Line:
If your horse normally runs very high in blood CO2, in the range very close to 37mmol/liter, due to supplementation with large amounts of sodium bicarbonate or other very high bicarbonate feed source, don't use Apple-A-Day. If, however, your horse consumes a normal diet or you know the blood CO2 level is low to average, you will not test positive for high blood CO2 and you’ll know you're using an excellent electrolyte/mineral supplement with Apple-A-Day. A telephone discussion with a member of Saratoga Gaming and Racing confirmed that typical intake of Apple-A-Day can not be a cause for high blood CO2 tests.

References:
1) L. Lawrence, K. Kline, P. Miller-Graber, A. Siegel, E. Kurcz, M. Fisher and K. Bump Dept. of Anim Sci., University of Illinois, Urbana 61801.