Poultry litter–induced endocrine disruption in fathead minnow, sheepshead minnow, and mummichog laboratory exposures

Animal feeding operations in the United States produce more than 500 million tons of manure annually. Disposal of poultry waste via application as fertilizer results in substantial runoff of poultry litter-associated contaminants (PLAC). Of particular concern are sex steroids, 17β-estradiol, estrone and testosterone, responsible for sex differentiation and development of reproductive structures. In a series of laboratory assays, mature male and mixed-sex larval/juvenile fish were continuously exposed to environmentally relevant PLAC solutions. Effects on gonads were assessed histologically, and vitellogenin (VTG) induction was measured as a gauge of estrogenicity. Twenty-one-day exposures to laboratory-generated PLAC solutions routinely induced VTG in mature male Pimephales promelas. Vitellogenesis in Fundulus heteroclitus only occurred at the highest tested PLAC concentration, and Cyprinodon variegatus were unresponsive at any tested concentration. All species produced considerable VTG in response to a 17β-estradiol-positive control. A pronounced feminization was seen in P. promelas when exposed to PLAC as larvae but not when exposed as juveniles. Runoff from a poultry litter-amended field cropped under standard agronomic practices induced significant VTG in male P. promelas. Results indicate that environmentally relevant PLAC concentrations exhibit endocrine activity sufficient to induce VTG production in male fish and possibly affect sex ratios in resident fish populations.