CONCENTRATIONS OF SALINOMYCIN IN EGGS AND TISSUES OF LAYING CHICKENS FED MEDICATED FEED FOR 14 DAYS FOLLOWED BY WITHDRAWAL FOR 3 DAYS

Laying chickens were fed medicated feed containing various concentrati ons of sodium salinomycin (SAL) for 14 days followed by a 3 day withdr awal period. Eggs, collected during treatment and withdrawal, tissues and ovarian yolk of birds slaughtered after 0, 1, and 3 days' withdraw al were extracted and analysed by high performance liquid chromatograp hy (HPLC). Tissues, ovarian yolk and freeze-dried egg albumen and yolk were extracted with acetone, followed by partitioning with petroleum ether and HPLC analysis. Albumen was extracted with methanol and analy sed without further clean-up. Salinomycin was detected at 520 nm after post-column reaction with vanillin at 95 degrees C. Recoveries of for tified salinomycin from freeze-dried eggs (albumen and yolk) and tissu e, premix and feed were nearly quantitative (>90%), except liver which was <85%. The detection limit was estimated to be 5 ng g(-1), with th e practical quantifiable limit being about 10 ng g(-1). Highest SAL co ncentrations were in the more fatty components such as egg yolk, ovari an yolk and subcutaneous fat. SAL residues in other tissues were gener ally low and followed the order liver, kidney, thigh and breast muscle s. SAL residues were dependent on the SAL concentration in feed and de clined rapidly during withdrawal.