Absorption of Diethylstilbestrol Pellets in Steers

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Abstract
Three experiments were conducted to determine absorption rate of diethylstilbestrol from 12-mg diethylstilbestrol pellets implanted subcutaneously in cattle. Residual diethylstilbestrol content was determined in 3 experimental lots of pellets excised from randomly-selected steers at 28, 56, 84 and 112 days subsequent to implantation. Absorption rate of the diethylstilbestrol from pellets followed closely that of a 1st order reaction. The half life of pellets 1, 2, and 3 was 80, 73 and 96 days, respectively. Over the 112-day period the quantities of stilbestrol absorbed daily per 12-mg pellet were 0.074, 0.073 and 0.056 mg for pellets 1, 2, and 3, respectively. Pellet 2 was selected for testing in feed-lot because rate of absorption suggested this pellet should be uniformly effective in stimulating additional gains for a 150-175-day period. In a 169-day fattening trial, pellet 2 increased gains over the total period with no indication that there was a reduction in rate of gain during the later phases of the trial.