Effect of repeated administration of combination trenbolone acetate and estradiol implants on growth, carcass traits, and beef quality of long-fed Holstein steers 1 J. M. Schefﬂer*, D. D. Buskirk*, S. R. Rust*, J. D. Cowley*, and M. E. Doumit*† 2 *Department of Animal Science and †Department of Food Science and Nutrition, Michigan State University, East Lansing 48824 ABSTRACT: Our objective was to determine the ef- fect of repeated use of implants on feedlot performance and carcass characteristics of Holstein cattle. Holstein steers (n = 128) weighing an average of 211 kg were blocked by weight and randomly assigned to 16 pens. At the start of the trial (d 0), pens were assigned to one of four treatments: 1) nonimplanted control (C); 2) implant on d 0, 112, and 224 (T3); 3) implant on d 112 and 224 (T2); and 4) implant on d 224 (T1). Component TE-S implants (120 mg of trenbolone acetate and 24 mg of estradiol per implant) were used for all treatments during the 291-d feeding period. Over the course of the study, T2 and T3 cattle had greater ADG and ﬁnal weights than C and T1 cattle (P < 0.05). Steers were harvested at a commercial abattoir on d 291. Hot car- cass weights of T3 steers were greater than those of C and T1 steers (P < 0.05). Dressing percentage, adjusted Key Words: Estradiol, Growth Promoters, Holstein, Tenderness, Trenbolone 2003 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2003. 81:2395–2400 Introduction The FDA approved the combination of trenbolone ace- tate and estradiol in 1991 for use in implants to increase rate of weight gain and to improve feed efﬁciency of cattle (FDA, 2003). The use of growth-promoting implants is currently widespread. In 1999, more than 96% of all cattle in feedlots were implanted at least once (NAHMS, 1 The authors thank K. Metz and the Michigan State University Beef Research and Teaching Center for collection of feedlot data; Murco Foods, Inc. for allowing access to carcasses and tissues; S. DeBar, J. Grobbel, and S. Scramlin for laboratory assistance, and A. McPeake-Abney and A. Grant for assistance with data analysis. Appreciation is expressed to the Michigan Animal Industry Coalition and the Michigan Agricultural Experiment station for project support. 2 Correspondence: 3385B Anthony Hall (phone: 517-355-8452, ext. 203; fax: 517-432-0753; E-mail: doumitm@msu.edu). Received December 23, 2002. Accepted June 16, 2003. 2395 12th-rib fat, percentage of kidney, pelvic, and heart fat, yield grade, and longissimus color were not different among treatments (P ≥ 0.26). Longissimus muscle areas (LMA) of T2 and T3 carcasses were larger than LMA of C (P < 0.01). No USDA Select carcasses were produced from C cattle, whereas the percentage of Select car- casses from implanted cattle ranged from 10 to 18%. Skeletal maturity advanced (P < 0.05) progressively with each additional implant. Steaks from T3 carcasses had a higher percentage of protein than controls (P < 0.05) and were less tender than all other treatments (P < 0.05). Repeated administration of combination trenbolone acetate and estradiol implants increased ADG and resulted in heavier carcasses with larger LMA. Administration of three successive implants de- creased tenderness of Holstein beef, and resulted in more advanced skeletal maturity scores. 2000). Combination trenbolone acetate and estradiol (TBA/E 2 ) implants may improve ADG and feed efﬁciency by as much as 20 and 13.5%, respectively, compared to nonimplanted cattle (Duckett and Andrae, 2000). How- ever, combination implants may have deleterious effects on beef tenderness (Thonney et al., 1991; Roeber et al., 2000) or USDA Quality Grade (Herschler et al., 1995; Foutz et al., 1997). The latter is attributed to reduced marbling, advanced skeletal or lean maturity, or a com- bination of these in implanted steers. In contrast, several studies have shown no effect of combination implants on quality grade (Hunt et al., 1991; Gerken et al., 1995; Johnson et al., 1996), or longissimus muscle tenderness (Apple et al., 1991; Hunt et al., 1991; Gerken et al., 1995). Repeated implanting of cattle with anabolic agents is common. This is particularly true for Holstein steers that are typically fed for longer periods and to heavier weights than cattle of beef breeds. However, it is not clear if growth beneﬁts or compromised quality result from repeated use of implants or if implants adminis- tered early in life decrease the effectiveness of implants