New approaches to detect cortisol administration in the horse

The cortisol threshold concentration of 1.0 mu g/ml in horse urine adopted by the International Federation of the racing Authorities in 1994 is specif ic. However, an increase in the sensitivity for the detection of cortisol a dministration would be helpful. Previous studies have shown that 20 beta-di hydrocortisol concentration in urine would be a good indicator of cortisol administration, The purpose of the present work was to estimate the populat ion parameters and the critical values of 20 beta-dihydrocortisol and 20 be ta-dihydrocortisone concentration in urine compared with that of cortisol, Using the same probability (1.1 x 10(-4)) which was used for the establishm ent of the official cortisol threshold, the critical values of 5000 ng/ml f or 20 beta-dihydrocortisol and 350 ng/ml for 20 beta-dihydrocortisone were obtained. Considering these 2 critical values for 20 beta-dihydrocortisol a nd 20 beta-dihydrocortisone, the time during which a horse could be declare d positive is significantly increased.