Relationship of ultrasonic and selected linear measurements of live animals with tissue development in heifers

Forty weanling Hereford heifers, ranging from 325 pounds to 625 pounds were used to compare live ultrasonic estimates of fat thickness and muscle depth with carcass fat thickness and muscle depth at thirteen anatomical locations, at approximately 60-day intervals, using the Branson Sonoray Model 12. The live ultrasonic estimates and carcass measurements of fat thickness and muscle depth also were compared with the pounds of separable muscle, fat and bone in the shankless round, retail cuts weight and retail cuts percent. The live ultrasonic fat thickness estimates more accurately measured fat thickness, shankless round separable muscle, fat and bone weight and retail cuts weight over the 1. dorsi and infraspinatus than over the b. femoris as compared to the carcass fat thickness measurements at these locations. When live ultrasonic estimates of muscle depth were compared to carcass measurements of muscle depth, the simple correlation coefficients between carcass measurements and shankless round tissue weight and retail cuts weight were superior, particularly in the 1. dorsi and infraspinatus. Several live animal and carcass linear measurements were taken and all measurements were significantly related to separable tissue weight and retail cuts weight except live b. femoris width x depth cm² and carcass rump length. Carcass weight accounted for the major portion of the variation in carcass composition due to the wide range in weight. It was concluded that additional physical separation data of heavier carcasses would have been needed to properly establish the patterns of muscle, fat and bone deposition.