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

Tanja M. HessDepartment of Animal and Poultry Science, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

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 DVM, MS
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David S. KronfeldDepartment of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

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 PhD, DSc, MVSc
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Carey A. WilliamsDepartment of Animal Sciences, Rutgers University, New Brunswick, NJ 08901.

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Jeannie N. WaldronRectortown Equine Clinic, 8446 Maidstone Rd, Rectortown, VA 20140.

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Patricia M. Graham-ThiersVirginia Intermont College, Bristol, VA 24201.

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Kathleen Greiwe-CrandellDepartment of Animal and Poultry Science, College of Agricultural and Life Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

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Marco A. LopesDepartment of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061.

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Pat A. HarrisWALTHAM Centre for Pet Nutrition, Melton Mowbray, LE14 4RT, UK.

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 MA, PhD, VetMB

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)

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)