RESUMO
The primary objective of this study was to compare the endocrine activity of wastes from trenbolone acetate:estradiol (TBA:E)-implanted steers to that of wastes from unimplanted steers. To accomplish this, fathead minnows (Pimephales promelas) were exposed to urine or fecal slurry from TBA:E-implanted or unimplanted steers for 7 days. Following exposures, hepatic vitellogenin (vtg) mRNA expression and secondary sexual characteristics were assessed. Among both males and females, there were no differences in vtg mRNA expression between fish exposed to urine from implanted or unimplanted steers at any of the concentrations tested. Furthermore, concentrations of steroid hormones in the urine of implanted and unimplanted steers were similar. These findings indicate a lack of differences in the endocrine activity of urine from TBA:E-implanted and unimplanted steers. With regard to the fecal slurry exposures, there were no significant differences in vtg mRNA expression among females from any of the groups; however, significant differences in male vtg mRNA expression were detected. Specifically, males exposed to 1600 mg dry feces/L from implanted cattle experienced an 840-fold increase in vtg mRNA expression relative to both unexposed males and males exposed to the corresponding fecal concentration from unimplanted steers. These males also appeared to experience a reduction in male secondary sexual characteristics. These findings suggest that steroids associated with the wastes from TBA:E-implanted steers have both feminizing and demasculinizing effects on male fish. Furthermore, these effects are most likely due to the presence of estrogenic compounds, which were detected in the liquid portion of the fecal slurry from TBA:E-implanted steers, but not in that of unimplanted steers. The findings of this study indicate the presence of endocrine-disrupting compounds in the urine and feces of cattle and suggest that the implant history of cattle alters the endocrine activity of feces, but does not alter the endocrine activity of urine.
