Numerous experiments during the past several years have shown that ear implants of diethylstilbestrol (DES and DES also as a feed additive), Synovex or zeranol (Ralgro) improve weight gain and feed efficiency of growing and finishing steers and heifers. The improvement has been reported from an early age throughout growing and finishing by reimplanting of the products at appropriate intervals. Improvement has been reported with numerous types of rations, but the degree of response may vary with the nutritional adequacy.
DES has been more widely used because of the greater amount of information on the product and lower cost in comparison to Synovex and zeranol. Since the banning of DES, there has been more interest in the response that might be expected from Synovex and zeranol. Implanting technique has also received considerable emphasis as to the effects on degree and uniformity of response from implants.
We have completed two experiments with finishing steers where responses to Synovex-S and zeranol were compared to nonimplanted controls. Two implanting sites were used for zeranol in each experiment.
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Department of Animal Science, Agricultural Experiment Station, South Dakota State University
Embry, L. B.; Goetz, M. J.; and Rosenboom, R. W., "Implanting Site for Zeranol Compared to Synovex-S for Finishing Steers" (1981). South Dakota Cattle Feeders Field Day Proceedings and Research Reports, 1981. 3.