Pork carcass grading: A comparison of the New Zealand Hennessy Grading Probe and the Danish Fat-O-Meater

Abstract

The left sides from 224 pork carcasses were probed for fat thickness and muscle depth at four locations (last rib, and between the third and fourth, fourth and fifth, and fifth and sixth ribs posterior to the last rib) and at three positions (5, 7 and 9 cm off the dorsal mid-line) using the Hennessy Grading Probe (GP) and the Fat-O-Meater (FOM). In addition, fat thickness was recorded at the loin (8 cm off the dorsal mid-line) using both instruments, and the caliper of the FOM was used to measure fat thickness at three positions over the medial face of the M. gluteus medius on the dorsal mid-line of the carcass. All pork sides were cut into five North American primals which were subsequently separated into fat, bone and lean to define percentage lean yield. The range in warm carcass weight and percentage lean yield varied from 58·5 to 94·5 kg and from 29·60 to 48·91%, respectively. The two probes differed little in precision for the prediction of percentage lean yield. Measurements taken with the GP and FOM between the third and fourth, and fourth and fifth last ribs gave the lowest residual errors. Position of measurements (5, 7 or 9 cm) had little effect on the relationship between lean yield and fat thickness or fat thickness and muscle depth. Addition of a second measurement fat thickness or muscle depth, provided only minor improvement in precision for the prediction of percentage lean yield over that of a single fat thickness measurement. The results suggest that, for grading systems using percentage lean yield as a basis, both the GP and FOM would provide similar precision, and that the choice of an instrument would then depend more on its durability and performance under commercial conditions.