Body Composition Evaluation
Data from two feeding trials were used to estimate accuracy of ultrasound measurements of fat thickness and ribeye area. In each trial, steers were scanned three or four times by one technician. Two beef improvement federation (BIF)-certified technicians with different levels of experience interpreted images from the last scan taken just before slaughter. Each technician interpreted the image of an individual steer twice on two different days. Accuracy of interpretation was evaluated using simple statistical measures, including means, standard deviations, regression and correlation coefficients, RMSE, and ESD. The overall technician biases for ultrasound measurements of fat thickness and ribeye area were -0.17 cm and 0.63 cm2, respectively. Mean bias by technician indicated a similar direction and amount of bias (-0.14 vs -0.20 cm). However, bias in the measurement of ribeye area by the two technicians took an opposite direction ( -1.28 vs 2.54 cm2). In all cases, technician bias was within the acceptable range for BIF certification. Pearson product moment correlations between carcass and ultrasound measurements of fat thickness and ribeye area were 0.70 and 0.40, respectively. In general, fat thickness for 52% of the steers was measured within ±0.254 cm and for 85.2 % of the steers, fat thickness was measured within ±0.508 cm. For ribeye area, ±51.2 % and ±71.4 % of the steers had measurements within ±6.65 cm2 and ±12.99 cm2, respectively .
Iowa State University
Hassen, A.; Wilson, Doyle E.; Rouse, Gene H.; Trenkle, Allen; Willham, Richard L.; Beliele, Deborah; Crawley, Catherine; and Iiams, J. C., "Evaluation of Ultrasound Measurements of Fat Thickness and Ribeye Area, I. Assessment of Technician Effect on Accuracy" (1997). Beef Research Report, 1996. 7.