The electronic prediction of commercial yield and lean content in pig carcasses

Abstract

ABSTRACTOne hundred and fourteen pig carcasses were measured within 1 h of slaughter for fat thickness at three locations using the SFK Fat-O-Meater. The three fat thickness locations were the last rib and 3rd and 4th last ribs measured 70 mm from the dorsal mid-line over the m. longissimus, and the lumbar fat thickness which was recorded on the anterior face of the m. glutens medius on the dorsal mid-line of the split carcass. Lean depth measurements were also recorded at the last rib and 3rd and 4th last ribs for all carcasses. After overnight chilling the leanness of each carcass was estimated using an EMME SA-1 machine. The carcasses were then separated into the major tissues. The weight of trimmed North American commercial joints (standard of 6 mm subcutaneous fat) and their lean content were best predicted by half carcass weight (residual s.d. = 0·78 and 1·23 kg respectively), whereas the EMME machine readings alone had low precision (residual s.d. = 1·51 and 1·41 kg respectively). The proportion of North American commercial joints in a carcass and their lean content were best predicted by lumbar fat (residual s.d. = 16·5 and 25·8 g/kg). The digital readout of lean content provided by the EMME machine appeared to be more related to carcass weight than lean weight, as residual s.d. for regressions increased when the overall sample was divided into two weight classes. Multiple regression equations indicated that half carcass weight and fat thickness measurements gave the best precision to predict joint and lean weights, whereas fat thickness and lean depth measurements gave the best prediction of carcass joint and lean proportions.