PREDICTING TOTAL WEIGHT OF RETAIL-READY LAMB CUTS FROM BIOELECTRICAL-IMPEDANCE MEASUREMENTS TAKEN AT THE PROCESSING PLANT

Data of sixty finished, crossbred lambs were used to develop predictio n equations of total weight of retail-ready cuts (SUM). These cuts wer e the leg, sirloin, loin, rack, shoulder, neck, riblets, shank, and le an trim (85/15). Measurements were taken on live lambs and on both hot and cold carcasses. A four-terminal bioelectrical impedance analyzer (BIA) was used to measure resistance (R(s), ohms) and reactance (X(c), ohms). Distances between detector terminals (L, centimeters) were rec orded. Carcass temperatures (T, degrees C) at time of BIA readings wer e also recorded. The equation predicting SUM from cold carcass measure ments (n = 53, R(2) = .97) was .093 + .621 x weight -.0219 x R(s) + .0 248 x X(c) + .182 x L -.338 x T. Resistance accounted for variability in SUM over and above weight and L(P = .0016). The above equation was used to rank cold carcasses in descending order of predicted SUM. An a nalogous ranking was obtained from a prediction equation that used wei ght only (R(2) = .88). These rankings were divided into five categorie s: top 25%, middle 50%, bottom 25%, top 50%, and bottom 50%. Within-ca tegory differences in average fat cover, yield grade, and SUM as a per centage of cold carcass weight of carcasses not placed in the same cat egory by both prediction equations were quantified with independent t- tests. These differences were statistically significant for all catego ries except middle 50%. This shows that BIA located those lambs that c ould more efficiently contribute to SUM because a higher portion of th eir weight was lean.