Posthatch oral estrogen exposure impairs adult reproductive performance ofzebra finch in a sex-specific manner

We determined whether short-term, posthatch oral exposure to estradiol benz oate (EB) or the industrial surfactant octylphenol (OP) could impair the re productive performance of zebra finches. If so, naturally occurring phytoes trogens and xenoestrogens might influence reproduction in wild populations. Chicks were given oral administration of 10 or 100 nmol EB per gram of bod y mass (earlier work showed the latter to be the minimum oral dose required to maximally masculinize female song nuclei) or an equimolar amount of OP daily from 5 through 11 days of age. Canola oil was used as a vehicle and c ontrol. Reproductive testing was done either in individual pair cages or in communal cages that permitted self-selection of mates, N = 10 pairs per gr oup. Pairs consisted of EB-treated males and females, EB-treated males pair ed with canola-treated females, vice versa, and canola-treated males and fe males. Posthatch EB treatment produced sex-specific impairments in reproduc tion that, in some instances, were additive when both sexes were treated. E gg production was reduced and egg breakage was increased in 100 nmol/g EB-t reated male and female pairs. The incidence of missing eggs was increased i n 10 nmol/g EB-treated male and female pairs. Candled fertility was reduced in both groups containing 100 nmol/g EB-treated males. The number of hatch ed chicks was severely reduced in all EB-treated groups. No adverse effects of OP treatment were detected. These significant treatment effects (all P < 0.05) show that posthatch EB treatment profoundly disrupts the reproducti ve performance of zebra finches, suggesting that exposure to estrogens in t he wild could impair the reproductive performance of wild populations. (C) 2001 Elsevier Science.