Weight loss, water loss and cation balance during the endurance test of a 3-day event

Authors


Department of Large Animal Clinical Sciences, University of Tennessee, College of Veterinary Medicine, PO Box 1071, Knoxville, Tennessee 37901–1071, USA

Summary

Bodyweights (BW) of 39 horses, competing in a 3-day event, were measured the evening before the endurance test (BW1), after phase D (BW2) and the next morning before stadium jumping (BW3). Plasma sodium concentration [Na1] was measured the evening before and after phase C of the endurance test [Na2]. Total body water (TBW1) was calculated using the formula (BW1 (kg) × 0.66 l/kg) and water loss (WL) was calculated as [(BW1 – BWx) X 0.9]. Cation balance (CB), the exchangeable cation concentration, was calculated using the formula [(TBW1(1) X Na1) - (TBW2(1)] X Na2). The decrease in BW and TBW averaged 17.4 ± 1.0 kg and 15.6 ± 0.8 litres respectively (mean ± s.e.m.) during the endurance test and remained decreased 9.2 ± 1.0 kg (BW) and 8.3 ± 1.0 litres (TBW) for 18 to 24 h after competition. Plasma sodium concentration after phase C of the endurance test (141.2 ± 0.3 mmol/l) was greater than resting values (138.8 ± 0.2 mmol/l), resulting in a net decrease in CB (-1601.1 ± 171.7 mmol). Significant water and electrolyte losses occur in horses competing in the endurance test of a 3-day event and these fluid losses persist for 18–24 h after this phase of competition.

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