Evaluation of ultrasound measurements of fat thickness and longissimus muscle area in feedlot cattle: Assessment of accuracy and repeatability

Abstract

Data from two cattle feeding trials were used to estimate accuracy and repeatability of ultrasound measurements of 12–13th rib fat thickness and longissimus muscle area. In each trial, images from the last scan prior to slaughter were interpreted by two certified technicians. Each technician interpreted the image of each steer twice on two different days. Overall technician biases for ultrasound measurements of fat thickness and longissimus muscle area were −0.17 cm and 0.63 cm2, respectively. Mean bias in measurement of fat thickness by the two technicians was similar in amount and direction (−0.14 cm vs. −0.20 cm); however, bias in the measurement of longissimus muscle area by the two technicians took an opposite direction (−1.28 cm2 vs. 2.54 cm2). Repeatability of ultrasound-measured fat thickness was the same for both technicians (0.96 to 0.97). However, measurements of technician A showed a better repeatability (0.92) than technician B (0.79) for ultrasound-measured longissimus muscle area. Generally, except for minor differences, degree of experience did not show a consistent difference in the accuracy of ultrasound estimation of fat thickness and longissimus muscle area. Hence, it was concluded that technicians could easily be trained to make accurate predictions of fat thickness and longissimus muscle area. Key words: Beef cattle, carcass, ultrasound, repeatability, accuracy