Early metabolic imprinting for improvements in finishing feed efficiency and beef carcass characteristics

Abstract Text: Recent research has indicated the ability of early nutritional intervention to metabolically imprint beef steers for enhanced carcass marbling.  As such, metabolic imprinting (IMP) has been suggested as an alternative management strategy to enhance beef quality.  The objectives of this experiment were to evaluate the impact of early IMP on finishing average daily residual feed intake (RFI), residual ADG (RADG) and carcass characteristics of backgrounded steers.  Angus- and Simmental-sired steer progeny from four calving seasons were stratified by sire and age within contemporary group and randomly assigned to metabolically imprinted (MI; weaned at 105 ± 18 d of age; n = 63) or conventionally weaned (CW; weaned at 210 ± 18 d of age; n = 42) treatment groups.  Following weaning, MI steers were adapted to and received a concentrate-based ration in a feedlot setting for 105 ± 45 d immediately prior to commingling with previously unsupplemented CW steers at the time of conventional weaning.  Commingled steers were then backgrounded for 150 ± 60 d prior to being finished on a concentrate-based ration for 110 ± 34 d.  Finishing ADFI and metabolic body weight collected at 28 day intervals were used to calculate RFI and RADG.  Steers were harvested in groups upon reaching an ultrasound predicted common 12th rib subcutaneous fat thickness (SFT) of approximately 1 cm.  Hot carcass weight was measured immediately prior to chilling.  Chilled (24 h) carcasses were evaluated by a trained panel of analysts to determine ribeye area, SFT, KPH and marbling score, as well as to calculate yield grade.  All statistical analyses were conducted using the Fit Model procedure of JMP Pro.  Analysis of a compiled dataset for main effects of treatment revealed that IMP resulted in an improvement in RFI (P < 0.05; -0.13 vs. 0.19 kg of TDN for MI and CW steers, respectively) without affecting RADG (P = 0.50; -0.01 vs. 0.01 kg for MI and CW steers, respectively).  Although ribeye area, SFT, KPH, marbling score and yield grade did not differ (P > 0.05) for carcasses of MI steers when compared to those of CW steers, IMP increased HCW (P < 0.05; 341 vs. 332 kg).  Collectively, interpretation of these results suggests the ability of IMP to increase HCW and decrease the amount of TDN required by finishing steers without negatively impacting ADG.     

Keywords: beef, imprinting, efficiency