Prediction of lean yield in yearling bulls using real-time ultrasound

A study was undertaken to determine the repeatability and accuracy of ultrasound measurements taken on yearling bulls and to assess the value of these live measurements to predict lean yield. Ultrasonic fat depth and 1. dorsi area were measured on 616 yearling bulls prior to slaughter. Corresponding carcass measurements were obtained through the Agriculture Canada Blue Tag Program. Carcass side lean (LEANYIELD) was extrapolated from the lean content of the seven-bone rib section from the carcasses of 41 Angus and 41 Charolais bulls. Stepwise multiple regression used live (USFAT and USREA) measurements to predict LEANYIELD. Repeatability (SER) and accuracy (SEP) statistics for USFAT were 0.8 mm and 1.6 mm, respectively. The corresponding results for USREA were SER = 4.3 cm(2) and SEP = 7.8 cm(2). The ultrasound lean yield (USLEAN) prediction equation was: USLEAN = 599.2 - (9.5 x USFAT) + (1.1 x USREA); R(2) = 0.73, RSD = 17.9 g kg(-1). Results indicated that LEANYIELD was predicted better by USLEAN (SEP = 18.0 g kg(-1)) than by BTLEAN (SEP = 22.6 g kg(-1)). Results from a second group of dissected bulls (n = 110) confirmed that ultrasound can predict LEANYIELD as effectively as carcass measurements (SEP = 22.8 and 22.6 g kg(-1) for USLEAN AND BTLEAN) in young breeding bulls in this study.