Effect of sex hormones on the retention of dieldrin in the fat of growing chickens.

The effects of the bird's sex, castration, and sex hormone replacement on the retention of dieldrin in the carcass fat of growing chickens given low levels of dieldrin in the feed (1 mg/kg) were investigated. Confirmed were previous results that "best-fit" curves for depletion after noncontaminated feed was provided were represented by an equation of the form, y = aX-b, and that, with the approach of sexual maturity, males tend to retain greater concentrations of dieldrin in the carcass fat than females. This sex difference was partly a diluting effect of higher carcass fat deposition in females as compared to males. Additionally, when dieldrin feeding was discontinued after 10 weeks of age, androgen replacement in castrates restricted the clearance of dieldrin from the fatty tissue, and estrogen replacement did not further increase clearance over that of nontreated castrates.