J. Anim Sci.
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J. Anim Sci. 1985. 61:1023-1029.
© 1985 American Society of Animal Science
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Comparison of the Performance of Estradiol Silicone Rubber Implant-Treated Steers to that of Zearalanol or Estradiol + Progesterone

R. P. Basson1, Wm. E. Dinusson2, L. Embry3, D. L. Feller1, P. E. Gorham1, H. P. Grueter1, D. D. Hinman5, J. McAskill1, C. Parrott1, J. Riley6, T. L. Stanton4, D. C. Young1 and J. F. Wagner1

Lilly Research Laboratories, Greenfield, IN

Abstract

A study was conducted at five locations to compare the growth response produced by an estradiol silicone rubber implant (E-SRI) in feedlot steers with that produced by a single or reimplant treatment of zearalanol (Z) and(or) estradiol + progesterone (E-P). The steers in the single-implant (SI) treatment group were treated with either Z or E-P. The steers in the reimplant (RI) treatment group received a single implant of either Z or E-P at the start of the experiment, and an E-P implant approximately 70 d after the start of the experiment. The data were evaluated at various intervals throughout the study in order to compare the effectiveness of the SI treatment with controls, RI and E-SRI treatments in relation to time. Before 70 d, the performance (average daily gain and feed conversion) of all implant treatments was significantly improved over controls. Before the RI group received the second implant, all implant groups performed similarly. By d 112, the SI treatment showed gains significantly less than RI and E-SRI treatments. By d 126, the SI treatment feed to gain ratio (F/G) was significantly larger than for the RI and E-SRI treatments. Throughout the study the performance of the steers in the RI and E-SRI treatment groups was similar. These data indicate that a single implant of either E-SRI, Z or E-P was fully efficacious for approximately 84 to 100 d. After that time, steers implanted with Z or E-P need to be reimplanted for a maximum implant response to be maintained.

Footnotes

1 Lilly Research Laboratories, Greenfield, IN.

2 North Dakota State Univ., Fargo.

3 South Dakota State Univ., Brookings.

4 Colorado State Univ., Fort Collins.

5 Univ. of Idaho, Caldwell.

6 Kansas State Univ., Manhattan.






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Copyright © 1985 by the American Society of Animal Science.