Residues from anabolic preparations after good veterinary practice

The purpose of this study was to determine the endogenous concentrations of estrogens, particularly estradiol-17 beta (E(2)beta), in edible tissues of beef cattle (females and intact and neutered males) and the concentrations of E(2)beta, and trenbolone beta and alpha (beta Tb, alpha Tb) after an E( 2)beta and/or trenbolone acetate (TA) ear implant. Radioimmunoassays were v alidated for quantitation Of E(2)beta (active isomer), E(2)alpha, estrone ( E-1), beta Tb and alpha Tb for bovine muscle, liver, kidney and fat tissues . The criteria of accuracy, precision, specificity and sensitivity were app lied according to the standards of the U.S. Food & Drug Administration. In steer tissues, endogenous E(2)beta was <15 ppt, as was heifer muscle; but h eifer liver and kidney were 3-fold greater. An E-2<beta> implant in steers had no effect on muscle E(2)beta concentration, but increased E(2)beta in l iver and fat 4- and 3-fold, respectively, but by 24 h post-implant removal, E(2)beta had fallen by half. Tissue E-1 concentrations in cyclic females w ere similar to E(2)beta, but rose many fold greater than did E(2)beta durin g gestation; E(2)beta rose 3-fold during gestation. After E(2)beta /TA impl ant, steer tissues had E(2)beta concentrations equal to (for muscle and fat ) and one-half (for liver) the E(2)beta measured in E(2)beta implant only s teers; beta Tb was in a low range (250-380 ppt) in muscle, liver and fat an d alpha Tb was even lower, except in liver (800-1500 ppt). An implant of TA only (no E(2)beta) resulted in beta Tb and alpha Tb concentrations 2-3-fol d greater in liver, kidney and fat, but no greater in muscle than beta Tb i n tissues of E(2)beta /TA implant steers. In conclusion, anabolic implants in steers resulted in tissue E(2)beta concentrations less than the beta Tb allowable increment and beta Tb in the lowest quartile (0.25) of a part per billion 30 days after implant.