The South African pig carcass classification system.

Abstract

The current regression equations for the prediction of pig carcass lean content in South Africa were calculated in 1992 and had not been updated since, whilst pig carcasses became much leaner and often heavier than the 90 kg originally used. It therefore became necessary to critically evaluate the classification regressions to establish whether the genetic improvement had a substantial effect on lean prediction and whether the same regression may be extrapolated to heavier carcasses. Ultimately, it must be established whether the producer is fairly remunerated. Eighty-one pigs, consisting of five representative genotypes and three sexes (gilts, boars and barrows) at a live mass between 20 kg and 30 kg, were allocated to eight slaughter groups, fed a standard diet ad libitum and slaughtered at live masses ranging from 74 kg to 160 kg. Fat measurements were taken on the carcasses using a Hennessy Grading Probe® and an Intrascope®, whereafter the left sides were divided into wholesale cuts and dissected into lean, fat, skin and bone. Fat measurements were also taken on the live animals prior to slaughter using a Renco Lean Meater®. Stepwise linear regression analysis was used to calculate regression equations between lean percentage and fat measurements as well as eye muscle diameter. Although the original equations still hold, even for heavier carcasses, alarming deviations from frequencies of observed carcass classifications were observed. This implies that either the producers are paid less than what they deserve, or the meat trade and consumer pay more than what they should. However, the price differences between both the two leanest classes and the two fattest classes are too small to have a significant effect on the price of pork.