Effects of veterinary antibiotics on the fate and persistence of 17β-estradiol in swine manure.

Abstract

The fate and persistence of natural estrogens from livestock manure and the interactions of these compounds with veterinary antibiotics (VAs) have not been well studied. We therefore employed 14C-labeling to explore the mineralization, degradation, and residual distribution of 17β-estradiol (E2) in swine manure in the absence and presence of six categories of VAs at concentrations of 10 and 100 mg/kg. After 16 days of incubation, 94% of the E2 dissipated, of which 28% was mineralized to 14CO2, 18% was transformed into organic-extractable E1 (9%) and other unknown metabolites (9%), and 48% into non-extractable residues (NER). VAs inhibited, enhanced or had no effect on E2 mineralization or its degradation to E1 and other metabolites. Principal component analysis showed that the overall effect of VAs was not necessarily related to their physicochemical properties or concentrations. However, high doses of macrolides inhibited E2 mineralization in manure and increased the retention of E2 and its metabolites in both free and NER forms. Our study demonstrates that considerable amounts of E2 and NER are retained in manure, despite nearly complete mineralization. Thus, VAs administered to livestock may increase the persistence of natural estrogens in manure and, accordingly, the environmental risks posed by these compounds.