Effects of oral potassium supplementation on acid-base status and plasma ion concentrations of horses during endurance exercise.
OBJECTIVE
To compare effects of oral supplementation with an experimental potassium-free sodium-abundant electrolyte mixture (EM-K) with that of oral supplementation with commercial potassium-rich mixtures (EM+K) on acid-base status and plasma ion concentrations in horses during an 80-km endurance ride.


METHODS
46 healthy horses.


METHODS
Blood samples were collected before the ride; at 21-, 37-, 56-, and 80-km inspection points; and during recovery (ie, 30-minute period after the ride). Consumed electrolytes were recorded. Blood was analyzed for pH, PvCO2, and Hct, and plasma was analyzed for Na+, K+, Cl-, Ca2+, Mg2+, lactate, albumin, phosphate, and total protein concentrations. Plasma concentrations of H+ and HCO3-, the strong ion difference (SID), and osmolarity were calculated.


RESULTS
34 (17 EM-K and 17 EM+K treated) horses finished the ride. Potassium intake was 33 g less and Na+ intake was 36 g greater for EM-K-treated horses, compared with EM+K-treated horses. With increasing distance, plasma osmolarity; H+, Na+, K+, Mg2+, phosphate, lactate, total protein, and albumin concentrations; and PvCO2 and Hct were increased in all horses. Plasma HCO3-, Ca2+, and Cl- concentrations were decreased. Plasma H+ concentration was significantly lower in EM-K-treated horses, compared with EM+K-treated horses. Plasma K+ concentrations at the 80-km inspection point and during recovery were significantly less in EM-K-treated horses, compared with EM+K-treated horses.


CONCLUSIONS
Increases in plasma H+ and K+ concentrations in this endurance ride were moderate and unlikely to contribute to signs of muscle fatigue and hyperexcitability in horses.
Hess
Tanja M
TM
Department of Animal and Poultry Science, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Kronfeld
David S
DS
Williams
Carey A
CA
Waldron
Jeannie N
JN
Graham-Thiers
Patricia M
PM
Greiwe-Crandell
Kathleen
K
Lopes
Marco A
MA
Harris
Pat A
PA
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000704:Analysis of Variance; D000818:Animals; D001774:Blood Chemical Analysis / Q000662:veterinary; D004573:Electrolytes / Q000097:blood / Q000494:pharmacology*; D006736:Horses / Q000502:physiology*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007477:Ions / Q000097:blood*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009994:Osmolar Concentration; D005082:Physical Exertion / Q000502:physiology*; D017419:Potassium, Dietary / Q000097:blood / Q000494:pharmacology*
D004573:Electrolytes; D007477:Ions; D017419:Potassium, Dietary