A comparison of two implant protocols; Synovex-Choice and Synovex-Plus vs. Synovex-S and Revalor-S on steer feedlot performance and carcass characteristics

Abstract Text: An experiment was conducted to determine the impact of two implant protocols on steer feedlot performance and carcass characteristics. Over a 2 yr period, 109 crossbred (5/8 Red Angus, 3/8 Continental) steers were randomly assigned to 1 of 2 implant protocols; 1) Synovex-Choice [100 mg of trenbolone acetate (TBA) and 14 mg of estradiol benzoate (EB)] implanted at the beginning of the feeding period (CHPL); or 2) Synovex-S (200 mg of progesterone and 20 mg of EB; SS) as initial implant. Steers were fed for approximately 100 d and the CHPL treatment was re-implanted with Synovex-Plus (200 mg of TBA and 28 mg of EB) while the SS treatment received Revalor-S (120 mg of TBA and 24 mg of estradiol). At 205 d on feed, steers were shipped to a commercial abattoir for slaughter. Carcass characteristics were evaluated 24 h following slaughter; HCW was determined on d of harvest. Average daily gain was similar (P = 0.39) for CHPL (1.75 ± 0.08 kg/d) and SS (1.70 ± 0.08 kg/d) steers. There was no difference (P = 0.37) in HCW for CHPL compared with SS steers (380 ± 7 vs. 374 ± 7 kg, respectively). Yield grade was also not affected (P = 0.16) by treatment, 2.5 and 2.7 ± 0.3 for CHPL and SS, respectively. There was no difference in LM area (P = 0.98) between CHPL and SS (90.52 vs. 90.52 ± 2.26 cm²), and back fat was also similar (P = 0.13) between the treatments (1.37 vs. 1.50 ± 0.15 cm, CHPL vs. SS, respectively). Marbling score was similar (P = 0.19) between treatments (501 vs. 525 ± 13, CHPL and SS, respectively) resulting in a similar percentage of steers grading USDA Choice [CHPL vs. SS, 93 ± 3% vs. 96 ± 3% (P = 0.42)] and upper 2/3 USDA Choice [CHPL vs. SS; 47 ± 7% vs. 54 ± 7% (P = 0.51)]. Net revenue was similar (P = 0.36) between CHPL ($1083.11 ± 37.83) and SS ($1103.43 ± 37.83) steers. Both implant regimens utilized in the current study resulted in similar feedlot and carcass characteristics.

Keywords: carcass characteristics, feedlot performance, implants