The effects of exercise, training, and a supplemental lecithin/corn oil diet on acid-base homeostasis and blood gases in arterial and central venous blood were examined during repeated sprint exercise in horses. Differences between temperature measurement sites for the adjustment of pH and blood gases during exercise was also investigated.

The independent variables, strong ion difference (SID), total weak electrolytes ([A_tot]), and pCO₂, had different effects on the dependent variables, [H⁺] and [HCO₃⁻], and these influences changed depending on blood sampling site (arterial or central venous), and exercise intensity. Data supporting the involvement of the chloride shift during repeated sprint exercise in the horse was observed for the first time.

Training resulted in increased plasma [Na⁺], [K⁺], [SID], albumin, free fatty acids, and beta~-hydroxybutyrate concentrations, and decreased blood lactate ([Lac⁻]), plasma [Cl⁻], [H⁺], cholesterol, and heart rate during exercise. Horses consuming the corn oil/lecithin supplemented diet had a higher pvCO₂, [HCO₃⁻], [Cl⁻], cholesterol, and glucose, and lower blood [Lac⁻], [H⁺], and triglycerides during exercise. The sprint training and corn oil/lecithin diet may act synergistically to enhance performance in horses’ by maintaining a lower [H⁺] during high intensity exercise.

There were differences between skin, rectal, blood, and muscle temperatures during incremental exercise and recovery in horses. The pH and blood gases adjusted to rectal, blood, and muscle temperatures were also different during exercise and recovery. Muscle and blood temperature may be predicted from rectal or skin temperature during exercise, and from skin temperature during recovery.