USE OF ULTRASOUND IN PREDICTION OF CARCASS CHARACTERISTICS IN LAMBS

Longissimus muscle area, maximum depth and maximum width and subcutane ous fat thickness were measured ultrasonically at the first lumbar ver tebra on 1162 lambs. Lambs were rams, ewes and wethers, ranging in age from 3 to 15 mo, with liveweights ranging from 32.5 to 70.2 kg. Subje ctive conformation scores of the leg, loin and shoulder and body-wall thickness at the GR site (11 cm from the carcass midline between the 1 2th and 13th ribs) were measured on warm carcasses and were used to de termine lean-meat yield. Saleable-meat yield and percentage of saleabl e-meat yield in each of the primal cuts were also determined by carcas s dissection of 57 of the lambs. Stepwise regression equations predict ing GR and lean-meat yield from ultrasound measurements, age, (age)(2) , liveweight and (liveweight)(2) had an R(2) of 0.49 and 0.47, respect ively (P < 0.15). Stepwise regression predicting saleable-meat yield b y carcass dissection from ultrasound measurements, age, (age)(2), live weight and (liveweight)(2) had an R(2) of 0.64, with subcutaneous fat as the only significant regressor (P < 0.001). Stepwise discriminant a nalysis used to predict leg, loin and shoulder conformation scores fro m ultrasound measures, liveweight, (liveweight)(2) (age)(2) and age ha d R(2) values of 0.27, 0.18 and 0.24, respectively (P < 0.15). From th ese data, ultrasound measurements of subcutaneous fat and longissimus depth in combination with liveweight and age appear to be valuable pre dictors of saleable-meat yield as determined by carcass dissection, GR and lean-meat yield but appear to be less useful in prediction of sub jective muscling scores, except in the case of small-frame lambs.