A comparison of 2 implant protocols-Synovex-Choice/Synovex-Plus versus Synovex-S/Revalor-S-on steer feedlot performance and carcass characteristics

An experiment was conducted to determine the effect of 2 implant protocols on steer feedlot performance and carcass characteristics. Over a 2-yr period, 109 crossbred (five-eighths Red Angus, three-eighths Continental; approximately 205 d of age; 242 ± 11 kg) steers were randomly assigned to 1 of 2 implant protocols: (1) Synovex-Choice [100 mg of trenbolone acetate and 14 mg of estradiol benzoate (EB)] implanted at the beginning of the feeding period, followed by Synovex-Plus (200 mg of trenbolone acetate and 28 mg of EB) approximately 100 d later (CHPL), or (2) Synovex-S (200 mg of progesterone and 20 mg of EB) as initial implant, followed by Revalor-S (120 mg of trenbolone acetate and 24 mg of EB) approximately 100 d later (SS). Average daily gain was similar (P = 0.39) for CHPL (1.75 ±  kg/d) and SS (1.70 ±  kg/d) steers. Yield grade was also not affected (P = 0.16) by treatment, 2.5 and 2.7 ±  for CHPL and SS, respectively. Marbling score was similar (P = 0.19) between treatments (501 vs. 525 ± 13 for CHPL and SS, respectively), resulting in a similar percentage of steers grading USDA Choice (CHPL vs. SS, 93 vs. 96 ± 3%; P = 0.42) and upper two-thirds USDA Choice (CHPL vs. SS; 47 vs. 54 ± 7%; P = 0.51). Net revenue was similar (P = 0.59) between CHPL ($1,255.97 ± 23.13) and SS ($1,237.78 ± 23.13) steers. Both implant regimens used in the current experiment resulted in similar feedlot performance and carcass characteristics.