Influence of steroid implants and concentrate feeding on performance and carcass composition of cull beef cows

Sixty nonpregnant, mature beef cows were used to evaluate the influence of steroid implants on performance and carcass composition of beef cows fed a high-concentrate diet. Twelve nonfed cows were slaughtered at 0 d. Remaining cows were stratified by weight and randomly assigned to an implant treatment and feeding period (28 or 56 d). Treatments included 1) no implant (control), 2) a 200-mg trenbolone acetate (TBA) implant, 3) a 200-mg testosterone propionate +20 mg of estradiol benzoate (TEB) implant, or 4) both implants (TBA + TEB). As days on feed increased, hot carcass weight (HCW), carcass soft tissue (CST) weight, adjusted fat thickness (AFT), longissimus muscle area (LMA), percentage of CST, and percentage of CST lipid increased (P < .05) and percentage of CST crude protein and moisture decreased (P < .05). Cows fed for 56 d accumulated (P < .05) more kilograms of lean than cows fed for 28 d, and cows fed for 28 d tended (P = .08) to have more kilograms of lean than nonfed cows. Cows fed for 56 d had (P < .05) higher dressing percentages than nonfed cows or cows fed for 28 d, and nonfed cows had (P < .05) higher dressing percentages than cows fed for 28 d. Implanted cows compared with control cows had (P < .05) heavier final weights, increased gains, improved feed efficiency, heavier hot carcass weights, larger LMA, higher cutability yield grades, compositionally leaner CST (higher percentage of moisture and protein and lower percentage of lipid), and more kilograms of lean. In addition, double-implanted (TBA + TEB) cows had (P < .05) more kilograms of CST than control and TBA-implanted cows. Furthermore, cows implanted with TBA had (P < .05) lower dressing percentages than TEB-implanted cows, less AFT than controls, and fewer kilograms of lipid than cows on the other three treatments. Full feeding of thin beef cows for 28 or 56 d increased carcass weight through an increase in CST lean as well as fat (lipid). The live performance and accretion of lean during realimentation can be enhanced by using anabolic implants.