An Iowa State University study compared ultrasound measurements of body composition of 145 heifers to their subsequent carcass measurements. The measurements were made on five separate harvest groups during the period of 2002 through 2004.

Overall results showed that ultrasound technology can accurately estimate ribfat thickness, ribeye area, and marbling prior to harvest. Correlations between live and carcass measurements were remarkably high for ribfat thickness and ribeye area at 0.80 and 0.66, respectively. The correlation for marbling score was lower at 0.48, but still significantly high (P<0.001). The authors concluded that real-time ultrasound is an accurate tool to measure body composition and can be used very effectively as a selection or sorting tool in the feedlot (Ribeiro et al. 2006. Iowa State Univ. Animal Industry Report).