134 Effect of Rumen Degradable Protein Intake on Performance, Carcass Quality, and Methane Emissions of Yearling Finishing Steers

Abstract The performance, economic, and environmental consequences of feeding rumen degradable protein (RDP) levels above below calculated maximum energy-dependent microbial crude (MCP) synthesis potential are poorly understood. Yearling steers (n = 54; initial BW 484.1 ± 26.03 kg) were assigned to one two pens that each contained an automated head chamber system (GreenFeed; C-Lock Inc., Rapid City, SD) for individual measurement enteric methane (CH4) emissions. Each steer was feed bunk (Calan Gate; American Calan, Northwood, NH) randomly three dietary treatments: low RDP intake (LRDPI; n 8), neutral (NRDPI; or high (HRDPI; 8) in a completely randomized design. Steers transitioned treatment diets utilizing two-ration blend 20-day followed by 80-day finishing period. Diets formulated provide cattle with similar metabolizable (MP) net energy gain (NEg) but different supply. approximately 87% (LRDPI), 100% (NRDPI), 113% (HRDPI) requirements maximize energy-allowable MCP-yield. Paired-day, unshrunk collected on d 0, 50, 80, transported commercial abattoir carcass data collection. Statistical analyses conducted using Analysis Variance JMP Pro6.0 the Fit Model procedure. Least-squares means differences considered statistically significant if P < 0.05 tendency toward ≤ 0.15. Treatment rations provided 94% 106% 118% required MCP yield, respectively. Daily DMI (P > 0.15) HRDPI NRDPI cattle, LRDPI tended 0.06) have less than cattle. Dietary did not affect ≥ 0.32) ADG, conversion efficiency, ribeye area, marbling score yield grade. Yet, had lighter hot weight 0.05) subcutaneous fat thickness whereas from other treatments. On average, emit 7.0% more daily CH4 (g×d-1; both HRDPI. Moreover, elicited 14.7% 18.1% increase CH4-yield (g CH4×kg DMI-1; 0.01) emission intensity ADG-1; compared treatments, These indicate limiting MCP-yield restricting may reduce while increasing results reiterate importance meeting suggest no performance benefits overfeeding RDP.