Effects of dietary and parenteral estrogens on bobwhite reproduction.

Bobwhites were fed one of several doses (.01 to 1,000 micrograms/day) of estriol (E3), beta-estradiol-3-benzoate (E2B), diethylstilbestrol (DES), or biochanin-A (BA) during two 10-week trials. The initial 2 weeks of each trial were short day length (10L:14D) followed by 8 weeks of long day length (16L:8D). In addition, female bobwhites were given daily injections containing dosages (.01 to 10 micrograms/day) of E2B, E3, and DES while housed on the same light regimen. Reproductive performance as assessed by onset of lay, egg production, and egg fertility was depressed in a dose-dependent manner and was inhibited by dietary dosages of 1,000 micrograms/day of E3, DES, and E2B. No consistent effects on reproductive performance were observed in bobwhites fed up to 1,000 micrograms/day of the phytoestrogen BA. Injected estrogens appeared approximately 100 times more potent than dietary estrogens. It was concluded that both dietary and parenteral estrogen can inhibit reproduction, but in order for phytoestrogen (BA) in natural feedstuffs to impair reproduction in bobwhites it would have to be consumed in excess of 1 mg/day.