220 A comparison of synovex one alone to synovex choice followed by synovex plus as implant strategies for finishing heifers

A commercial feedyard study utilizing crossbred heifers (n = 1,737; initial BW 313 kg) fed for 182 days compared the effect of two implant strategies on performance and carcass characteristics. The study design was a randomized complete block with block as arrival date and initial BW; with pen as the experimental unit (12/treatment). Heifers were implanted with Synovex ONE Feedlot [200 mg trenbolone acetate (TBA), 28 mg estradiol benzoate (EB)] on d 1 (ONE), or implanted with Synovex Choice (100 mg TBA, 14 mg EB) on d 1 followed by Synovex Plus (200 mg TBA, 28 mg EB) on d 95 (CH/Plus). Statistical analysis was conducted using the Mixed procedure of SAS with treatment and block considered fixed effects for performance. Quality grade (QG) and yield grade (YG) data were analyzed using the GLIMMIX procedure of SAS. Implanting with Ch/PLUS tended to improve ADG and HCW (P ≤ 0.13) compared to implanting with ONE. Heifers implanted using ONE tended (P = 0.09) to have greater DMI than CH/PLUS heifers. Intakes were similar (P = 0.34) between treatments before re-implanting, but CH/Plus heifers had lower (P < 0.01) DMI in the final 85 days. Heifers implanted using CH/PLUS had significantly (P < 0.01) greater G:F calculated on a carcass basis compared to heifers implanted with ONE. Heifers implanted with CH/PLUS had significantly (P ≤ 0.02) lower marbling score and YG, higher dressing percentage, and greater LM area compared to heifers implanted with ONE. Heifers implanted with ONE tended to have improved QG distribution (P = 0.06) but poorer YG distribution (P = 0.09) compared to heifers implanted using CH/PLUS. These data suggest that implanting heifers with Synovex ONE Feedlot resulted in slightly less efficiency but better quality grade when fed equal days compared with using Synovex Choice and Plus reimplant program.