Comparison of a single extended-release implant and a re-implant strategy on performance and carcass characteristics of beef finishing heifers

Abstract

Objective

A commercial feedlot experiment evalu- ated the effects of implanting heifers with an extended- release implant (Synovex One Feedlot) compared with a re-implant strategy (Synovex Choice followed by Synovex Plus) on finishing heifer performance, animal health, and carcass characteristics.

Materials and Methods

Using a randomized com- plete block design, crossbred heifers (n = 1,737; initial BW = 313 kg ± 15.3 kg) were randomly assigned to 24 pens across 2 treatments for an average of 181 d experi- ment. Treatments included a single extended-release im- plant administered on d 0 (Synovex One Feedlot; ONE) or a re-implant strategy of Synovex Choice (d 0) followed by Synovex Plus (CH/PLUS) on d 93 to 95.

Results and Discussion

There were no differences in live final BW or ADG between the 2 implant strate- gies; however, heifers implanted with CH/PLUS had 2.5% greater carcass-adjusted feed efficiency than ONE heif- ers. The CH/PLUS strategy produced heavier hot carcass weight (387 vs. 384 kg), larger LM area (87.9 vs. 85.3 cm²), and greater DP (62.30% vs. 61.96%) compared with ONE. Heifers implanted with ONE had greater marbling score, calculated YG, and 12th-rib fat (1.97 vs. 1.89 cm) compared with CH/PLUS heifers, resulting in a difference in QG and YG distribution between the 2 implant strate- gies. No differences were observed between treatments in morbidity, mortality, or pen removals.

Implications and Applications

These results indi- cate that heifers receiving a more aggressive re-implant strategy have heavier hot carcass weight, greater yield, and larger LM area, but reduced marbling compared with heifers that received an extended-release implant.