Comparison of the effects of long-acting Synovex One with Revalor-XS and Synovex Plus on growth performance and carcass quality in steers1

Two studies were conducted with beef steers to compare the effects of long-acting implants Synovex One (SYN-ONE) and Revalor-XS with each other and with the shorter-acting implant Synovex Plus (SYN-PLUS) on growth performance and carcass quality. Steers (n = 240, initial BW = 384 ± 4.0 kg) in Nebraska were administered SYN-ONE, SYN-PLUS, or Revalor-XS 161 d before slaughter. Steers (n = 300, initial BW = 262 ± 3.6 kg) in Texas were administered the same implants 200 d before slaughter. Each experiment was conducted according to a randomized complete block design with 10 blocks of 3 treatments and pen as the experimental unit. Blocking was based on pretreatment BW, and treatments within a block were assigned to contiguous pens. On d 0, steers were weighed and received assigned implants. Steers were fed finishing diets and were weighed twice more during each experiment and on 2 consecutive days before slaughter in commercial facilities for carcass evaluation. Statistical-analysis models included the fixed effect of treatment and random effects of block and block by treatment interaction and residual; BW and ADG were analyzed as repeated measures. Overall growth performance did not differ (P > 0.05) among implant groups in either location. However, there were differences (P < 0.05) in BW, ADG, and G:F between treatments during some intermediate intervals, i.e., SYN-PLUS was greater than SYN-ONE during the first interval and SYN-ONE was greater than SYN-PLUS during some of the later intervals. Carcass characteristics did not differ (P > 0.05) among implant groups. It was concluded that the 3 implants were equally efficacious.