93 - Equivalent Effects of Growing Phase ADG and DOF at Various Placement Weights on Finishing Beef Cattle Performance Using Meta-analysis Approach

A meta-analysis approach was used to interpret effects of growing phase days and rate of gain on finishing performance at theoretically similar maturity using a dataset derived from 53 manuscripts. Growing phase feeding strategies included dry-lot feeding a high-energy finishing diet post-weaning (HG; n = 16), silage (DL-forg; n = 32) or a moderate energy diet (DL; n = 78), stocking cattle on winter wheat (WW; n = 16) or range (GR; n = 43). Independent variables of interest were initial growing phase body weight (initial BW), growing phase average daily gain (ADG), days-on-feed in growing phase (DOF), and final growing phase body weight. Data were analyzed using the PROC MIXED procedure of SAS, with treatment means weighted by experimental units (EU) per treatment. Optimal combinations of growing phase DOF and initial BW differed between models. Yet, for dressing percent (R² = 0.39), LMA (R² = 0.55), final finishing BW (R² = 0.58), and HCW (R² = 0.54) models, an 80-d growing phase for cattle starting at 240 kg resulted in greatest responses by these variables. Simulations evaluating effects of growing phase ADG on finishing performance (dressing percent; LMA; final body weight; HCW) were set equivalent to simulations evaluating the sensitivity of growing phase DOF in response to initial BW. Solving these simulations generated the initial BW at which cattle were more responsive to growing phase length (DOF) than ADG (LMA_{critical point} = 255 kg; DP_{critical point} = 242 kg; Final finishing BW_{critical point} = 231 kg; HCW_{critical point} = 233 kg). For finishing performance traits listed, each critical point represents the inflexion at which growing phase ADG exerts greatest influence on each trait modeled. Thus, for example, for cattle starting a growing phase at under 233 kg, faster growing phase ADG results in greater hot carcass weight response.