A COMPARISON OF TWO ULTRASONIC TECHNIQUES FOR THE MEASUREMENT OF FAT THICKNESS AND RIB EYE AREA IN CATTLE

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Abstract
A comparison of two ultrasonic techniques, A-mode and B-scan, using two commercially produced ultrasonic machines, Krautkramer Model USM 2F (A-mode) and Scanogram Model 721 (B-scan), was made for the measurement of fat thickness and rib eye area in cattle. Two experiments were conducted. Experiment 1 included 107 Hereford steers of approximately 454 kg liveweight and experiment 2 included 65 heifers of mixed breeding of approximately 375 kg liveweight. The B-scan results in both experiments were analyzed by two interpreters and the A-mode results were analyzed by one interpreter in experiment 1 and by two interpreters in experiment 2. All cattle were slaughtered after measuring with ultrasonics, and corresponding carcass measurements were taken 48 h postmortem. Both ultrasonic techniques were approximately equal in accuracy (σd) and precision (r) for the measurement of fat thickness. The correlations (r) and standard deviation of differences (σd) for the rib eye area estimates were highly dependent upon operator skill, particularly for the A-mode technique. For the experienced skilled operator, the A-mode technique was shown to be comsiderably more accurate and precise. The B-scan method was faster for obtaining and interpreting measurements. Rib eye area was estimated from two rib lean depth measurements using the A-mode technique with a high degree (R2 =.72) of precision.

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