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 influenc e of steroid implants on performance and carcass composition of beef c ows fed a high-concentrate diet. Twelve nonfed cows were slaughtered a t 0 d. Remaining cows were stratified by weight and randomly assigned to an implant treatment and feeding period (28 or 56 d). Treatments in cluded 1) no implant (control), 2) a 200-mg trenbolone acetate (TEA) i mplant, 3) a 200-mg testosterone propionate + 20 mg of estradiol benzo ate (TEB) implant, or 4) both implants (TBA+TEB). As days on feed incr eased, hot carcass weight (HCW), carcass soft tissue (CST) weight, adj usted fat thickness (AFT), longissimus muscle area (LMA), percentage o f 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 lea n than nonfed cows. Cows fed for 56 d had (P < .05) higher dressing pe rcentages 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 C ST (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 TEA-im planted cows. Furthermore, cows implanted with TEA 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 weigh t through an increase in CST lean as well as fat (lipid). The live per formance and accretion of lean during realimentation can be enhanced b y using anabolic implants.