Which ratio should be adopted to evaluate the urinary excretion of testosterone and epitestosterone in veal calves?

- Control of the illicit use of endogenous hormones in meat producing animals requires a detailed knowledge of both the metabolism of endogenous hormones and their physiological profiles in each species. Nowadays current approaches in cattle do not involve the determination of the absolute urinary concentration of endogenous hormones because no validated physiological levels are recognised; the same is true when the ratio between metabolites is considered, as applied for testosterone (T) and epitestosterone (E) in athletes (1). In man, urinary epitestosterone has attracted the attention as a reference substance in the doping control of testosterone abuse. The nearly constant urinary ratio of T to E (T/E) in adults became the basis of the method of detection of exogenously administered testosterone, since in humans epitestosterone does not originate from exogenous testosterone in significant amounts (2). Data from literature (2,3,4) reported that in cattle epitestosterone is a metabolite of testosterone probably produced in liver and blood by hydroxysteroid-oxido-reductase enzymes via androstenedione. Aim of the study was a preliminary approach to assess physiological concentrations of T and E in urine of veal calves, and to evaluate which urinary ratio could be useful to indicate hormone treatments in calves. - The results reported showed that, despite the large variations of T and E concentrations in urine collected from veal calves, the physiological excretion of E was about ten times greater than T, and E excretion tends to decrease with increased age, as reported in young and adult men (2). Since in men urine concentrations of E and T are quite similar, and the excretion of E remained rather constant when exogenous T was administered; a cut-off value for T/E in urine was established for doping control (5). In a previous paper we applied the T/E ratio approach to urine of veal calves, but the influence of treatment was masked and no significant difference were observed between treated and control calves (6). Now, our recent data, confirmed that repeated treatments with natural hormone could cause a time-course reduction of urinary E as already reported (3, 7); applying the E/T ratio, the reduction of E urinary excretion was confirmed in Testosterone treated (A) but not in Boldenone treated calves (B and C).