ELECTROMAGNETIC SCANNING TO PREDICT LAMB CARCASS COMPOSITION

The electromagnetic scanner generates a constant, low-level electromag netic field (2.5 MHz) within a large plexiglass tube. The amount of el ectromagnetic (EM) energy transferred (to the carcass) is highly relat ed to lean tissue. A plot of the absorption units over distance can be used to assess the total mass of lean tissue and of the respective pr imal cuts. The difference in curve height between two points (D), peak phase absorption, and linear carcass measurements (pre-rigor, HCWT or postrigor, CWT carcass weight, and carcass length, LENG) were used to predict total dissected lean (TOTLEAN), dissected leg lean (LEGLEAN), and percentage of dissected carcass lean (PERLEAN). Twenty-one pre-ri gor and 22 post-rigor (24 h chill) lamb carcasses, average weight 26.8 (+/- 4.2 kg) and 26.4 (+/- 4.1 kg) kg, respectively, were evaluated f rom measurements of total body electrical conductivity (TOBEC). Two ge ometric orientations were tested for statistical accuracy in this stud y: A) each carcass entered the EM tunnel rear leg first, on its left l ateral side, neck facing the right side of the tunnel; and B) each cai cass entered the EM tunnel rear leg first, breast down, and neck up. Orientation A proved more statistically efficient for pre-rigor carcas ses, and orientation B was more desirable for post-rigor carcasses. Mu ltiple-regression models involving HCWT, LENG, and a single D measure accounted for 98.0 and 95.0%, respectively, of the total variation in pre-rigor carcass TOTLEAN and LEGLEAN in A. The regression model invol ving CWT, PEAK, and a single D measure accounted for 94.2% of the vari ation in TOTLEAN of carcasses scanned post-rigor, and CWT and two diff erent D measures accounted for 92.2% of the variation in LEGLEAN. Perc entage of pre-rigor carcass lean was best predicted in A, and B was mo re statistically efficient for carcasses scanned post-rigor. The best- fit equation for predicting percentage of pre-rigor carcass lean inclu ded LENG, PEAK, and two D measures (R(2) = .763). Percentage of carcas s lean was best predicted by a four-variable equation including three D measures and carcass length (R(2) = .775) when post-rigor carcasses were scanned. The results of this preliminary study indicate that EM s canning is effective for predicting the composition of lamb carcasses.