EFFECT OF USING ULTRASONIC MUSCLE DEPTH AND FAT DEPTH ON THE ACCURACYOF PREDICTED PHENOTYPIC AND GENETIC VALUES OF CARCASS TRAITS ON LIVE RAM LAMBS

Ultrasonic scanning was used to measure muscle depth and fat depth at the third lumbar vertebra of 556 ram lambs of the Norwegian Dala and S paelsau breeds in three ram circles in 1990. After slaughter, carcass weight, carcass grade, muscling score, fat score and weight of kidney and kidney fat were recorded. The increase in accuracy of predicting c arcass weight and grade by including ultrasonic measurements in additi on to weaning weight was low, whereas a considerable increase in accur acy of fat score was observed for Dala. A genetic analysis of 355 reco rded progeny sired by 44 young Dala rams was made. Estimates of herita bilities from the REML procedure were: 0.46 +/- 0.22 for muscle depth and 0.26 +/- 0.17 for fat depth. Genetic correlations were estimated. The accuracy of the selection indexes for carcass weight, carcass grad e or fat score increased significantly when ultrasonic measures were a dded compared to use of weaning weight and sire records only.