Fat (and muscle) thickness measurements were carried out in five slaughterhouses on 174 selected carcasses to compare the Hennessy Grading Probe (HGP) with the Renco Lean-Meater (Renco) and Pie Medical ultrasonic devices for their ability to predict the lean meat proportion of pig carcasses. The day after selection, all left carcass sides were dissected according to the simplified European Union (EU) reference method. In addition 44 of these sides were further dissected according to the full EU reference method.

In a further set of slaughterhouses it was found impossible to measure fat thickness with the Renco and Pie Medical ultrasonic device due to extreme singeing of the carcasses. From the five slaughterhouses, between third and fourth from last rib, 6 cm off the dorsal mid line, observations on fat thickness with HGP and Pie Medical were similar but observations with Renco were significantly lower (F < 0·001). Correlations between fat thickness measurements taken with HGP, Renco and Pie Medical all exceeded 0·95.

In terms of residual standard deviations of prediction formulae, the HGP performed highly better than Renco or Pie Medical (23·7, 25·1 and 24·9 g/kg respectively). These results, together with practical problems, make the use of ultrasonic measurements under practical conditions at present less feasible than using the HGP.