Influence of virginiamycin supplementation on growth performance, carcass characteristics, and liver abscess incidence, with 2 different implant strategies in calf-fed Holstein steers

Abstract

Our goal was to determine the effect of virginiamycin supplementation and 2 different implant strategies on growth performance, carcass characteristics, and liver abscess incidence in calf-fed Holstein steers. Following an initial 112-d receiving-growing period, 120 Holstein steer calves (287 ± 14 kg) were blocked by BW into 5 groups and randomly assigned within BW groupings to 20 pens (6 steers per pen, 5 pen replicates per treatment). Two levels of supplemental virginiamycin (0 vs. 16 mg/kg, 90% DM basis) and 2 growth implant strategies (Synovex One vs. Synovex Plus on d 1 and 112) were evaluated in a 2 × 2 factorial arrangement of treatments. There were no treatment interactions (P > 0.20). Virginiamycin supplementation increased overall (d 1–197) ADG (6.8%, P < 0.01) and BW gain efficiency (6.1%, P < 0.01). Compared with a single long-duration implant, the re-implant program increased initial 112-d (8.3%, P < 0.01) and overall 197-d (7.5%, P < 0.01) ADG. Enhancements in ADG were due to increased DMI (3.4%, P = 0.04) and efficiency of energy utilization (2.9%, P = 0.04). Across all treatments, liver abscess incidence was low, averaging 5.8%. Virginiamycin supplementation increased carcass weight (4%, P = 0.01). Compared with a single long-duration implant, the re-implant program increased carcass weight (2.8%, P = 0.04) but decreased marbling score (9.1%, P = 0.02). Virginiamycin supplementation enhanced ADG, BW gain efficiency, and estimated dietary NE. Single long-duration implants may not afford the same growth and gain efficiency response as conventional re-implant programs for calf-fed Holstein steers. Although, marbling score may be improved.