Abstract #746

Section: Beef Species
Session: Beef Species
Format: Oral
Day/Time: Wednesday 4:30 PM–4:45 PM
Location: Panzacola F-1
# 746
Alternative weaning and finishing strategies affect finishing residual feed intake of beef steers.
Jason K. Smith*1, Deidre D. Harmon1, Mark D. Hanigan2, Samer W. El-Kadi1, Sally E. Johnson1, Scott P. Greiner1, Mark A. McCann1, 1Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, 2Department of Dairy Science, Virginia Tech, Blacksburg, VA.

Recent evidence suggests that alternative early nutritional management strategies may metabolically imprint beef steers for reductions in finishing residual feed intake (RFI). To further evaluate this effect, as well as that of an alternative finishing nutritional management strategy, a 2 × 2 × 2 factorial experiment was conducted that included Angus (ANG) and Simmental (SIM) sired steers randomly assigned to one of 2 weaning treatments (early weaned [EW; weaned at 111 ± 23 d or age; n = 14] or conventionally weaned [CW; weaned at 233 ± 21 d of age; n = 14]) and one of 2 finishing treatments (high corn [HC; 68.7% of DM from steam-flaked corn; n = 14] or low corn [LC; 50% of DM from steam-flaked corn isoenergetically replaced with dried corn gluten feed; n = 14]). EW steers were fed a concentrate-based ration ad libitum for 122 d following weaning. All steers were then commingled and backgrounded on pasture for 190 d, finished in a feedlot for 154 ± 64 d, and harvested in groups upon reaching a common 12th-rib fat thickness of 1 cm. Feed intake was measured daily following a 42 d finishing ration adaptation period using a Calan-Broadbent system. Observed ADFI expressed in Mcal of NEg was regressed against average BW0.75, ADG and duration of the measurement period (R2 = 0.73; P < 0.0001) via the Fit Model procedure of JMP Pro, and RFI was calculated as the difference between observed and predicted ADFI. Analysis of variance was conducted to determine the fixed main and interaction effects of sire breed, weaning treatment and finishing treatment on ADFI, ADG and RFI. Although no effects were observed for ADFI (P ≥ 0.45) or ADG (P ≥ 0.36), RFI of ANG HC steers was lower than ANG LC (−0.91 vs. 0.49 Mcal NEg; SEM = 0.22; P < 0.001), SIM LC (−0.91 vs. 0.20 Mcal NEg; SEM = 0.22; P < 0.01) and SIM HC (−0.91 vs. 0.10 Mcal NEg; SEM = 0.22; P < 0.05), and was lower for EW than CW steers (−0.27 vs. 0.21 Mcal NEg; SEM = 0.15; P < 0.05). These results provide additional evidence of metabolic imprinting of EW steers for reductions in RFI, and independent effects of finishing energy source on RFI of ANG steers.

Key Words: early weaning, metabolic imprinting, residual feed intake