A comparison of four ultrasonic machines (sonatest, scanogram, Ilis Observer and Danscanner) for predicting the body composition of live pigs

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Abstract
Measurements of the m. longissimus and overlying fat at the last rib were taken on the live pig using ultrasonic machines of differing complexity: Sonatest (simple A-mode machine), Scanogram and His Observer (modified linear scanners), and Danscanner (‘real time’ scanner). These measurements were examined as predictors of the corresponding carcass measurements and percentage lean in the carcass.Sonatest and Scanogram were compared using 143 purebred and crossbred pigs of different types. The analysis was pooled within breed-type and sex. The standard deviation for percentage lean was 3·94. Residual standard deviations for predicting percentage lean from live weight and best fat thickness were 2·72 (Sonatest) and 2·56 (Scanogram). Addition of m. longissimus depth (Sonatest) and m. longissimus area (Scanogram) reduced these to 2·69 and 2·29 respectively. The use of two or more fat measurements provided no extra precision over a single fat measurement.Scanogram and His Observer were compared using a subset of 38 pigs. Scanogram was a better predictor of percentage lean using a single fat measurement but when a combination of measurements was used, there was little difference between the machines.Scanogram and Danscanner were compared using a subset of 27 pigs. The standard deviation of percentage lean was 3·57. Residual standard deviations for predicting percentage lean from live weight, best fat depth and m. longissimus area were 2·18 (Scanogram), and 2·03 (Danscanner). Fat areas had similar predictive precision to fat thickness measurements.