The objectiveof this work was to obtain equations to estimate hot carcass weight (PCQ) anddressing percentage (RC) from ultrasound measurements (US) of 48 young bullsof the Brangus and Nellore breeds, fed diets with 20, 40, 60 or 80% of concentrate.Ultrasonic measurements made with a PieMedical Scanner 200 Vet equipment, withlinear array transducer of 178 mm coupled with standoff guide, were ribeye area(AOLU), backfat thickness (EGSU) between 12ª and 13ª ribs and thefat thickness over the Biceps femoris (EGPU) muscle and live weight werecollected on intervals of approximately 28 days. Regression equations for eachbreed and an overall equation were established. The best equations were selectedthrough the Cp statistics. Correlations between measurements taken by ultrasoundand after slaughter were 0.83 between AOLU and carcass area and 0.86 betweenEGSU and carcass backfat. Equations to estimate PCQ showed greater accuracywhen measurements were taken closer to slaughter. However, equations to estimateRC showed lower accuracy and showed no improvement closer to slaughter. Theoverall equation showed the same or less accuracy for both characteristics ifcompared to equations of each breed. Predictions of PCQ and RC using ultrasoundmeasurements showed results similar to those using the same measurements takendirectly on carcass. The EGPU measurement did not increase the accuracy of predictionswhen EGSU already in model.
