An evaluation of two ultrasonic machines (Scanogram and Danscanner) for predicting the body composition of live sheep

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Abstract
Scans of the m. longissimus and overlying fat at the 12th rib were taken, just prior to slaughter, on 254 lambs using the Scanogram and Danscanner ultrasonic machines. The lambs were from a ram breed trial and comprised six sire breed × five dam breed groups. Mean live weight at slaughter was 44·5 kg.The precision with which scan measurements predicted comparable carcass measurements and carcass lean content (g/kg lean) was examined within groups with variation in live weight eliminated.Residual s.d. for the prediction of carcass m. longissimus area from the corresponding scan measurement was 141 and 158 mm2 for the Scanogram and Danscanner respectively (s.d. of carcass m. longissimus area was 162mm2). Residual s.d. for the prediction of lean from the best combination of fat measurements was 32·0 for the Scanogram and 35·8 for the Danscanner (s.d. of lean was 38·5). M. longissimus did not increase the precision of lean prediction.In a comparable evaluation of the Scanogram, involving 147 lambs, the residual s.d. for the prediction of lean was 24·0 (s.d. = 28·9).The levels of precision obtained were low and it is debatable whether the ultrasonic techniques examined would be of value for carcass lean prediction in practical applications. They might be of use in selection programmes within nucleus flocks of the more important meat sire breeds or as an aid in experiments for differentiating between animals of widely differing composition.