Urinary Cortisol excretion in the resting and exercising horse
Version of Record online: 10 JUN 2010
© 1995 EVJ Ltd
Equine Veterinary Journal
Volume 27, Issue S18, pages 457–462, May 1995
How to Cite
TOUTAIN, P. L., LASSOURD, V., POPOT, M. A., LAROUTE, V., ALVINERIE, M. and BONNAIRE, Y. (1995), Urinary Cortisol excretion in the resting and exercising horse. Equine Veterinary Journal, 27: 457–462. doi: 10.1111/j.2042-3306.1995.tb04973.x
- Issue online: 10 JUN 2010
- Version of Record online: 10 JUN 2010
The aim of this study was to document the 24 h urinary Cortisol concentrations during a rest day and a day that included prolonged exercise. The influence of exercise on disposition (plasma, urine) of a dose of Cortisol (1 mg/kg) was also assessed. Six adult saddle horses were used. In one experiment, urinary Cortisol elimination rates were measured during rest and prolonged exercise (56 km, 12 km/h) corresponding to about 50% of the V̇O2max. In another experiment, horses received, according to a crossover design, an intravenous (i.v.) bolus administration of Cortisol (1 mg/kg) either at rest or during the same prolonged exercise.
The urine Cortisol concentration was lower than 100 ng/ml in the control resting horse. It was increased by exercise but the maximal concentration was lower than 300 ng/ml and returned to control values by 10 h after the end of exercise. After 1 mg/kg Cortisol i.v. Cortisol clearance was decreased by exercise (552 ± 143 vs. 452 ± 59 ml/kg/h, mean ± s.d.), but the difference was not significant The peaks of urinary Cortisol ranged from 760 to 21,967 ng/ml and occurred 0.8 to 6.9 h after Cortisol administration depending on the time of the first urination after administration. The return to values below 100 ng/ml was observed after 21 h in all horses. The 1000 ng/ml threshold for Cortisol control in urine after i.v. Cortisol (1 mg/kg) is specific (conservative) but of low sensitivity.