USE OF ELECTRONIC PROBES FOR CLASSIFYING LAMB CARCASSES

Three commercially available electronic lamb carcass grading probes (H ennessy Grading Probe, AUS-Meat Sheep Probe, Swedish FTC Lamb Probe) a nd one developmental probe (Ruakura GR lamb probe) were assessed for a ccuracy and suitability for use on-line on the lamb dressing chain for objectively classifying lamb carcasses. GR is the total tissue thickn ess over the 12th rib taken at a distance 11 cm from the mid-line, use d to define fatness in lamb carcass grading in New Zealand. Probe meas urements were compared with manually measured GR (sometimes used at pr esent) and Toland probe measurements (total tissue depth between the r ibs) for accuracy of predicting both GR on the right side of the carca ss and also carcass water (indicating muscle) and fat content. Probes were tested on six occasions, each having approximately 50 lambs. All probes combined with carcass weight accounted for over 70% of the vari ation (R2) of GR right, with GR left accounting for 92% of the variati on of GR right. Inclusion of a quadratic probe term was not quite as u seful as inclusion of carcass weight for predicting GR right. The thre e commercial electronic probes individually when combined with carcass weight could account for 36-49% of the variation in the percentage of water and fat in the carcass, with the manual GR probe (right) on the chilled carcass accounting for 55% of the variation in water and 58% of the variation in fat percentages. Chilled carcass measurements are expected to give better results than readings on hot carcasses. The us e of a quadratic probe coefficient instead of carcass weight with the probe readings gave similar accuracy of prediction of carcass composit ion. There was little difference between the two sides in the accuracy of prediction. Small differences were found between regressions relat ing probe readings to GR and composition for the different probing occ asions. The electronic probe results from this trial are consistent wi th overseas results where probes are in use for objectively grading th e carcasses of meat animals.