The growth and breed-related changes of rib and rump characteristics in lean beef cattle and the ability of ultrasound
to predict carcass traits were investigated. Three hundred bulls from three breeds were scanned monthly
(6–7 times) using real-time ultrasound with final scans taken b7 days prior to harvest. The rib and rump ultrasound
measurements, except intramuscular fat content, increased (P b 0.05) with live weight. Breed affected
most of traits. The 12th rib ultrasound measurements showed a weak to high positive correlation (0.131 to
0.976, P N 0.05 to P b 0.001) with 12th rib measurements in the carcass. Regression equations developed with
the ultrasound measurements, explained 97% of the variation in longissimus muscle area, 88% of the variation
in fat thickness and 57% of the variation in intramuscular fat content. When last ultrasound scan measurements
were excluded fromprediction equations, the R2 significantly decreased. Ultrasoundmeasures “in vivo” are viable
options for assessing carcass attributes of lean cattle.