Ultrasonic probe data were available on 199 crossbred pigs (98 females, 101 barrows). These animals were probed at approximately 30, 50, 70, 100 and 120 kg live weight with two probing instruments (Krautkramer USM2, Combison 310) at three sites along the back. The measurements were examined as predictors of the proportion of valuable cuts (part dissection) and estimated lean concentration (at 100 and 120 kg live weight).
The standard deviations for proportion of valuable cuts (after correcting for sex effects) were 24·8, 26·7, 23·4, 27·1 and 29·4 g/kg at 30, 50, 70, 100 and 120 kg. Residual s.d. for predicting proportion of valuable cuts from live weight and ultrasonic probes (Combison, quotient fat to muscle area) were 190, 20·9, 19·3, 213 and 19·6. For the USM2, the residual s.d.s were 19·2, 26·3, 19·9, 25·1 and 24·6. Thus the Combison probe provided a better prediction of proportion of valuable cuts. The standard deviations of estimated lean concentration as determined by a Fat-O-Meater reflectance probe were 28·9 and 39·3 at 100 and 120 kg live weight. The residual s.d.s from live weight and ultrasonic measurements were 15·4 and 19·2 for the Combison probe and 21·5 and 20·5 for the USM2 probe. If the estimated lean concentration is accepted as a selection objective the value of ultrasonic probes as criteria in selection indices will increase.