Occurrence, Fate and Transport of the Primary Metabolites of Trenbolone Acetate in CAFO Soils and Surface Water Runoff

Abstract

Metabolites of synthetic growth promoters used in industrial cattle production pose a demonstrated ecological risk to waterways adjacent to beef feedlot operations. For example, numerous studies have linked reproductive abnormalities in fish species to the presence of 17-α trenbolone and 17-β trenbolone, the primary metabolites of the synthetic steroid trenbolone acetate. Therefore, to measure steroid concentrations of these metabolites in feedlot runoff, a series of rainfall simulation experiments were conducted on research feedlots at the University of California, Davis, Animal Science Facility. Soil samples were also collected from a commercial feedlot to assess the occurrence of trenbolone acetate metabolites in confined animal feeding operation (CAFO) surface soils following implantation. To quantify steroid concentrations, a gas chromatography/tandem mass spectrometry (GC/MS/MS) analytical method was developed and applied to the analysis of solid and aqueous samples. 17α- trenbolone, 17β-trenbolone, and trendione, the three primary metabolites of trenbolone acetate, occurred in both solid and aqueous phase samples. Steroid concentrations on solid samples were assessed by solvent and aqueous phase extraction on both aged and unaged feedlot soil and manure samples. Organic solvent extraction followed by GC/MS/MS analysis yielded average 17α-trenbolone and 17β-trenbolone concentrations of 8.2 (±1.1) ng/g and 1.2 (±0.1) ng/g respectively, with concurrent detection of trendione at lower concentrations. Parallel aqueous phase extractions of the solid materials were able to extract approximately 64% of the steroid mass extracted by organic solvents, indicating that the majority of steroid mass on solids is water extractable and potentially mobile. Consistent 17α-trenbolone metabolite concentrations ranging from 1 to 350ng/L, and trendione concentrations ranging from 1 to 170 ng/L, were observed in simulated CAFO runoff. The metabolite 17β-trenbolone intermittently occurred in samples throughout the experiments at concentrations ranging from 5 to 26 ng/L and may be correlated to anoxic conditions within the feedlot surface soils. These trenbolone acetate metabolite concentrations observed in the feedlot runoff correspond to 5-15% of the maximum steroid concentration predicted by mass balance approaches. Results suggest that environmentally relevant concentrations of 17α-trenbolone, 17β-trenbolone, and trendione can be mobilized on beef feedlot surfaces during storm events, and may lead to environmental concentrations at or above the threshold (11 ng/L for 17α-TbOH) for sexual alteration in cases of uncontrolled runoff.