|Fritsche, Sonja - VISITING ARS SCIENTIST|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2001
Publication Date: N/A
Interpretive Summary: Hormonal growth promoter implants approved in the U.S. include estrogenic, androgenic, and combination formulations. This study compared the relative response to three of these products (Synovex-S, Ralgro, and Revalor-S) in beef steers and across different times or ages in the feedlot. Relative response to these implants was similar over time with the greatest effect to implants occurring during the first period of the feeding study. Implants improved daily gain, efficiency, and carcass weight, Longissimus muscle area, 6-to 12-rib weght, and estimated carcass lean. The combination Revalor-S implant appeared to result in the strongest response with regard to performance and lean carcass growth.
Technical Abstract: The comparative influence of three approved hormonal growth promoter ear implants was studied at three time periods during a growth and finishing trial on both the growth performance of beef steers and their carcass merit and estimated edible carcass composition. Sixty-four steers of predominantly Charolais breeding in a 175-d feeding trial were fed a diet of 30% Corn:alfalfa silage (1:1) and 70 % corn-based concentrate and assigned to four implant treatments (Control, no implant; Synovex -S; Ralgro ; Revalor -S). Steers were slaughtered at 49, 112, and 175 d. There were no implant by feeding period or age interactions (P > .10). Performance, carcass merit, and estimated composition changed with feeding period as expected. Relative responses to Synovex-S, Ralgro, and Revalor-S compared to controls were 20.6%, 15.2%, and 30.4% (P < .01) for daily gain, 6.7%, 7.1%, and 9.5% (P < .05) for carcass weight, 10.4%, 10.6%, and 15.7% (P < .10) for Longissimus muscle area, and 8.4%, 10.2%, and 11.8% (P < .10 for estimated carcass lean, respectively. The response patterns to implant products were similar across time, and the combined adrogen-estrogen formulation Revalor gave the strongest response in performance and carcass lean growth.