Measurements were carried out on 200 selected carcasses in order to investigate whether single or multiple site measurements could provide an accurate estimation of the lean meat proportion in the carcass and the major cuts i.e. ham, shoulder, loin and belly. Fat measurements were taken with the Hennessy Grading Probe II at 17 sites on the left side of the carcass, and muscle measurements at four of these sites. The day after selection 200 left sides were dissected according to the simplified European Community (EC) reference method.
Fifty of these left sides were further dissected according to the full EC reference method. The use of multiple site measurements, compared with a single site measurement, only slightly reduced the residual s.d. of the estimated lean meat proportion in the carcass and the major cuts, e.g. addition of a second site measurement reduced the residual s.d. values by 0·3 to 1·3 gjkg only. The measurement between the 13th and 14th thoracic vertebrae, 7 cm off the dorsal mid line, appeared to be the best single estimator, of the sites probed, for lean meat proportion in the carcass and in the major cuts. Prediction of lean meat proportion in the belly appeared to be problematic (residual s.d.> 29 g/kg).
During the experiment two problems emerged. Firstly, the algorithm, which calculates fat and muscle thickness from the optically measured tissue profile, was not appropriate for every site. Secondly, the definition of the probing position did not always coincide with the anatomical position of the intended superficial layer of muscle underneath the subcutaneous fat.