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Influence of Hormone Implants on Gains Made on Native Pastures and in the Feedlot, and on Carcass Characteristics of Yearling Steers^{1, 2,}

The University of Nebraska, Lincoln and The United States Department of Agriculture

Abstract

The influence of hormone implants on daily gains and feeder grade of steers grazed under range conditions was studied in two experiments involving 78 and 288 steers. Implants of 24 mg. of stilbestrol and implants containing 200 mg. progesterone and 20 mg. estradiol benzoate increased daily gains by 8 to 11 %. An implant containing 60 mg. 17-alpha-hydroxy-progesterone caproate, 60 mg. testosterone enanthate, and 24 mg. estradiol valerate increased daily gains about 2%, but this difference was not significant. There was no difference in feeder grade between the treatments.

After the summer grazing period the group of 288 steers were subdivided and part of the steers were reimplanted. The steers were then placed in feedlots and full-fed to choice slaughter grade. The implants, increased the rate of gain 12 to 22% when compared with gains of steers receiving no implant in either the summer or feedlot periods. One implant in either the grazing or the feedlot phase seemed to be as satisfactory as an implant in each phase so far as average daily gain over both periods was concerned. The steers that were not implanted in either period required 10 days longer to reach choice slaughter grade, but they did have a higher carcass grade than the other groups. There was no difference in days required to reach choice slaughter grade between the various treated groups.

There were small but significant differences in carcass grade due primarily to differences in marbling. There was no significant difference in rib-eye area, fat thickness, or dressing percent between the various treatments. The implanted steers required less feed per 100-lb. gain, but the differences were not statistically significant.

¹ Published with the approval of the Director as Paper No. 932, Journal Series, Nebraska Agricultural Experiment Station.

² Grateful acknowledgment is made to E. R. Squibb & Sons, New Brunswick, New Jersey, for grant-in-aid in support of these experiments (A. D. Rankin, D.V.M., Associate Medical Director). Acknowledgment is also made to Geo. H. Hormel & Co., Fremont, Nebraska, especially Mr. Roger A.Orr for the excellent cooperation received in securing the carcass data. The authors also express their appreciation to Mr. John A. Rothlisberger for supervision of the care and feeding of the cattle throughout these experiments.