Using early ultrasound measurements to predict beef carcass quality grade

Abstract Text: Although many cattle producers have focused selection efforts toward enhancing carcass marbling, a number of pre- and post-weaning management factors often limit the ability of finished cattle to achieve their marbling potential.  Enhancing the ability of a feeder to predict finished quality grade (QG) prior to entry into a finishing program would allow for more strategic utilization of management practices that impact QG, particularly for cattle with lower likelihood of achieving QG-based retail brand acceptance.  The objective of this experiment was to evaluate the ability of early ultrasound measurements collected prior to finishing to predict finished carcass marbling score (MS) and QG.  Serial early ultrasound measurements of ribeye area (REA), twelfth-rib subcutaneous fat thickness (SFT) and percent intramuscular fat (IMF) were collected from early- and conventionally-weaned Angus-sired steers (N = 60) from three separate calving seasons within a single herd.  Ultrasound measurements were collected at the time of early-weaning (EW; 105 ± 18 d of age), conventional-weaning (CW; 210 ± 18 d of age), and again upon conclusion of backgrounding (360 ± 60 d of age) immediately prior to feedlot arrival.  Cattle were adapted to a concentrate and corn silage-based ration and finished for 131 ± 34 d at one of two feedlots prior to being harvested upon reaching a common ultrasound predicted SFT of 1 cm.  Carcasses were evaluated by a panel of trained analysts to determine MS and QG.  Initial screening for factor effects of weaning treatment, sire, and ultrasound predicted REA, SFT and IMF measurements for each of the three time points via the screening procedure of JMP Pro (version 10.0.2; SAS Institute, Cary, NC) indicated that IMF and REA measurements collected at CW and immediately prior to feedlot arrival explained a significant (P < 0.05) portion of the variation in carcass MS.  Full four-way factorial regression models were then generated to predict carcass MS (R² = 0.83; P < 0.05) and the probability of achieving a specific QG (R² = 0.95; Χ² = 129; P< 0.0001) using the Fit Model procedure of JMP Pro.  These results provide evidence that early carcass measurements for REA and IMF can be effectively utilized to explain a major portion of the variation in finished carcass MS and QG.  Such information could be utilized to produce models that allow feeders to predict carcass QG at receiving.

Keywords: beef, quality, marbling