ASSESSMENT OF LAMB CARCASS COMPOSITION FROM LIVE ANIMAL MEASUREMENT OF BIOELECTRICAL-IMPEDANCE OR ULTRASONIC TISSUE DEPTHS

Market weight lambs, average weight 52.5 kg (+/-6.1), were used to eva luate nontraditional live animal measurements as predictors of carcass composition, population (n = 106) represented lambs and transcended g eographic location, breed, carcass weight, yield grade, and production system, Realtime ultrasonic (RU) measurements and bioelectrical imped ance analysis (BIA) were used for development and evaluation of predic tion equations for % boneless, closely trimmed primal cuts (BCTPC), we ight or % of dissected lean tissue (TDL), and chemically derived weigh t or % fat-free lean (FFL). Longitudinal ultrasonic images were obtain ed parallel to the longissimus thoracis et lumborum (LTL), positioning the last costae in the center of the transducer head. Images were sav ed and fat and LTL depths were derived from printed images of the ultr asonic scans, Bioelectrical impedance analysis Was administered via a four-terminal impedance plethysmograph operating at 800 mu A at 50 kHz . Impedance measurements of whole-body resistance and reactance were r ecorded. Prediction equations including common linear measurements of live weight, heart girth, hindsaddle length, and shoulder height were also evaluated. All measurements were taken just before slaughter. Bio electrical impedance measurements (as compared to RU and linear measur ements) provided equations for %BCTPC, TDL, %TDL, FFL and %FFL with th e highest R(2) and lowest root mean square error. Even though BLA prov ided the best equations of the three methodologies tested, prediction of proportional yield (%BCTPC, %TDL, and %FFL) was marginal (R(2) = .2 96, .551, and .551, respectively). Equations combining BIA, RU, and Li near measurements greatly improved equations for prediction of proport ional lean yield.