Absorption of Diethylstilbestrol Pellets in Steers

Abstract

In three experiments a total of 41 steers were implanted with experimental 12-mg. diethylstilbestrol pellets. In each experiment pellet residues were removed from randomly selected steers at 28, 56, 84 and 112 days subsequent to implantation. The rate of absorption of the diethylstilbestrol from the pellets was found to follow closely that of a first 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 at least 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.