PLASMA ESTRADIOL-17-BETA CONCENTRATIONS IN THE COW DURING INDUCED ESTRUS AND AFTER INJECTION OF ESTRADIOL-17-BETA BENZOATE AND ESTRADIOL-17-BETA CYPIONATE - A PRELIMINARY-STUDY

Plasma estradiol‐17ß concentrations were investigated in cows during induced estrus and after an intramuscular injection of 10 mg of estradiol‐17ß benzoate and estradiol‐17ß cypionate to determine a withdrawal period for both preparations. After the estradiol‐17ß benzoate injection, the plasma estradiol‐17ß concentration was higher than the physiological maximum of 24 pg/ml obtained during induced estrus for a period of 114±10 h (mean±SEM). For estradiol‐17ß cypionate the corresponding value was 170ß17h (mean±SEM). A withdrawal period of 7 days for the benzoate ester and of 10 days for estradiol‐17ß cypionate is therefore proposed. These results were confirmed by biopsies taken at the injection site 8 and 15 days after the injection of estradiol‐17ß benzoate and estradiol‐17ß cypionate, respectively. In these biopsies no residues of estradiol‐17ß nor of its esters could be detected. Copyright © 1990, Wiley Blackwell. All rights reserved