John Wiley & Sons, Ltd.

Characterization of trenbolone acetate and estradiol metabolite excretion profiles in implanted steers

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Exogenous growth promoters have been used in United States beef cattle production for over 50 years. The environmental fate and transport of steroid growth promoters suggest potential for endocrine disrupting effects among ecological receptors; however, the initial excretion of steroid metabolites from cattle administered growth promoters has not been well characterized. To better characterize excretion of trenbolone acetate and estrogen metabolites, steers were assigned to one of the following treatment groups: control, given no implant, or treatment, administered a combination implant (200 mg trenbolone acetate; 40 mg estradiol). Blood, urine, and fecal samples were collected over the course of 112 days following implantation. Samples were extracted and analyzed by liquid chromatography tandem mass spectrometry for trenbolone acetate and estrogen metabolites. In both urine and feces, 17á‐trenbolone and 17á‐estradiol were the predominant metabolites following implantation. Mean concentrations of 17á‐trenbolone and 17á‐estradiol in feces of implanted steers were 5.9 ± 0.37 ng/g and 2.7 ± 0.22 ng/g, respectively. A best‐fit model is presented to predict 17átrenbolone and 17á‐estradiol excretion from steers receiving implants. The present study provides the first characterization of both trenbolone and estrogen metabolites in excreta from implanted cattle and will help provide estimates of steroid production from feedyards in the United States. Environ Toxicol Chem © 2014 SETAC

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