Prediction of the Chemical Composition of Sheep by Use of Ultrasound

The merit of an ultrasonic machine (Scanogram) to predict carcass chemical composition in vivo was evaluated from data collected on 37 Suffolk rams. Rams averaged 72.5 kg of live weight at scanning. Ultrasonic measurements were determined for subcutaneous fat at the sternum, third coccygeal vertebra and last rib and for bodywall thickness at the scapula. Residual standard deviations were used to indicate the precision achieved in predicting ether extract, protein and ash of rams at equal live weight. Ultrasonic area measurements did not significantly improve precision relative to linear measurements. Linear measurements determined at the sternum and scapula sites did not (P>.05) predict variation in composition. Each linear measurement at the third coccygeal vertebra (0 and 50 mm lateral to the midline) explained variation in ether extract (P<.01), protein (P<.01) and ash (P<.05). Depth of fat 80 and 140 mm lateral to the midline of the last rib each accounted for variation in ether extract (P<.05) but not for protein or ash. The most informative ultrasonic measurement for each compositional trait was depth of fat at the midline of the third coccygeal vertebra, a scanning site not previously investigated. Addition of a second ultrasonic measurement to the prediction equation also affected ether extract (P<.05), but had marginal effects on protein (P>.10) and ash (P<.10). Prediction equations developed from ultrasonic measurements provided insufficient precision to encourage broad use of the Scanogram as a research tool for sheep.