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Effects of oral potassium supplementation on acid-base status and plasma ion concentrations of horses during endurance exercise

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  • 1 Department of Animal and Poultry Science, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
  • | 2 Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
  • | 3 Department of Animal Sciences, Rutgers University, New Brunswick, NJ 08901.
  • | 4 Rectortown Equine Clinic, 8446 Maidstone Rd, Rectortown, VA 20140.
  • | 5 Virginia Intermont College, Bristol, VA 24201.
  • | 6 Department of Animal and Poultry Science, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
  • | 7 Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.
  • | 8 WALTHAM Centre for Pet Nutrition, Melton Mowbray, LE14 4RT, UK.

Abstract

Objective—To compare effects of oral supplementation with an experimental potassium-free sodiumabundant 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.

Animals—46 healthy horses.

Procedure—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 and Clinical Relevance—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. (Am J Vet Res 2005;66:466–473)