Carcass characteristics of the heifers are given in Table 4. No differences (P > .05) were observed for any of the carcass character- istics except for marbling score, although ribeye area tended to be greater with the high level of testosterone. Carcass composition has been similar for implanted and control heifers in previous work . The 35-d implant withdrawal period may have removed differences in carcass composition at slaughter. A similar reduction in marbling score has been observed in steers implanted with trenbolone acetate