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Implant Absorption, Performance and Tissue Analysis for Beef Steers Implanted with Diethylstilbestrol and Fed an All-Concentrate Diet

U. S. Department of Agriculture, Beltsville, Maryland 20705

Abstract

Four lots of 16 steers each were fed an all-concentrate diet and each steer was administered two ear implants equivalent to 30 mg total diethylstilbestrol (DES). At 14 days, one steer from each lot was slaughtered for tissue samples of muscle, kidney and liver and the residual implants were retrieved from the ears of these slaughtered steers. Residual ear implants were retrieved from all remaining steers in lots 1, 2, 3 and 4 at 28, 56, 84 and 119 days, respectively. At these times, five steers from the respective lots were slaughtered for tissue samples and 10 steers were returned to the lots to complete the feedlot trial after surgical removal of the implants. At 119 days, ruminal fluid samples for pH and volatile fatty acid analyses were obtained from the steers that had been returned to each lot, and then the steers were slaughtered. The absorption of DES from ear implants followed the exponential curve y = 11.6e ^-.014X, where y = mg DES, e = base of the natural logarithm and x = days. Rate of gain did not differ among lots, and only slight differences in ruminal pH and VFA were noted among lots. Feed efficiency, carcass grade and carcass yield were similar for the 84- and 119-day lots, and greater for those lots than for the 28- and 56-day lots. There was an average incidence of 79% abscessed livers. DES, measured by gas-liquid chromatography techniques with a lower limit of sensitivity of 0.5 ppb, was not found in ß-glucuronidase hydrolyzed extracts of muscle and kidney tissues or liver tissue obtained 56, 84 and 119 days after implantation. The concentration of DES and its glucuronide conjugate was near 0.5 ppb for some liver tissue samples during the first month after implantation. In a second trial, steers were implanted with 30, 60 or 120 mg DES per steer. There was no apparent increase in the concentration of DES and its conjugate in tissues relative to the level of implanted DES.

¹ ARS, Nutrition Institute, Ruminant Nutrition Laboratory.

² The authors gratefully acknowledge the advice and assistance of Mr. R. M. Simpson and Drs. J. E. Spaulding and A. J. Malanoski of U.S.D.A., Animal and Plant Health Inspection Service, in setting up the GLC procedure for tissue analysis of DES and for conducting duplicate analyses of samples.