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The Efficacy of an Estradiol-Silicone Rubber Removable Implant in Suckling, Growing and Finishing Steers¹

Oregon State University, Eastern Oregon Agricultural Research Center, Burns 97720 and Union 97883

Abstract

Sixty steer calves, 42 Simmental x Hereford and 18 Hereford, averaging 59 days of age and 78 kg, were assigned to six estradiol-17β implant treatments. Implants were cut from cylindrical formed tubes containing a mix of 80% nonpolymerized silicone and 20% microcrystal-line estradiol-17β by weight and cut into lengths that provided 0, 8.5, 15.6, 30.7, 30.9 and 46.7 µg estradiol-17β/day over a 499-day trial period. Two types, a coated and solid implant, were tested at the 31-µg level; all others were coated with a solid placebo used for the 0-µg or control treatment. Animal performance was recorded through the suckling, growing and finishing phases of production, and carcass data were collected. Cummulative gains over the 499 days were greater (P<.05) for the steers given the 30.9- and 46.7-µg levels than for those given the 0-, 8.5- and 15.6-µg levels, with respective daily gains being .97 and .97 vs .90, .90 and .89 kg; steers given the implant delivering 30.7 µg daily tended to gain more (P<.10) than the controls: .95 vs .90 kilograms. These values represent a 6% increase in gain over the control with the 30.7-kg coated implant and an 8% increase with the 30.9-µg solid and 46.7-µg coated implants. Implants did not improve feed efficiency during a 65-day feedlot period. Neither the amount of estradiol-17β nor the type of implant significantly influenced any carcass parameters except maturity. As the dose rate increased, the degree of carcass maturity increased. Type of implant did not affect gain during any period or any of the carcass measures. Results of this study indicate that a single implant of estradiol-17β delivering approximately 30.7 µg/day will improve weight gains over a long period of time and increase carcass maturity grade of steers.

¹ Tech. Paper No. 5432, Oregon Agr. Exp. Sta.

² Eastern Oregon Agricultural Research Center, Squaw Butte Station.

³ Eastern Oregon Agricultural Research Center, Union Station.

⁴ Eli Lilly and Co., Vancouver, WA.