tilapia seemto be unaffected by relatively small amounts of estrogens in
the feed. Nonetheless, despite ether extraction, hexane washing and
Sep-Pak purification,measurable amounts of E2were still found in squid
and vegetables, equivalent to 90 pg/g and 80 pg/g respectively, possibly
due to residual cross-reaction with the E2 antibody. Vitellogenin
production however, remains a reliable indicator of estrogenic activity,
and it is convincing that the squid-based diet contains negligible
amounts of estrogenic compounds