Relationships Between Body Measurements Obtained on Yearling Brangus Bulls and Measures of Carcass Merit Obtained from Their Steer Clone-Mates

Abstract

This study was designed to determine the relationship between ultrasonic and linear body measurements of yearling bulls and percentage retail product (pRP) of slaughter steers using genetically identical bulls and steers as experimental animals. Four groups of Brangus, second-generation nuclear transfer calves (two steers and two to four bulls per clone group) were used in this study. Serial (every 28 d) measurements of hip height (HH), body length (BL), rump length (RL), rump width (RW), shoulder width (SW), round mass (RNMS), metacarpal length and circumference (MCL and MCC), metatarsal length and circumference (MTL and MTC), and ultrasonic measurements of backfat thickness (BFT), Longissimus muscle area (LMA), Longissimus muscle depth (LMD), body wall thickness (BWT), rump fat thickness (RFT), and rump muscle depth (RMD) obtained on each bull from weaning (6 to 7 mo) until 16 to 17 mo of age were regressed on age to obtain 365-d age constant estimates for the traits. Steers were slaughtered between 480 and 520 d of age and percentage of retail cuts (trimmed to 0.64 em) was obtained. Genetic correlations of the adjusted traits of the bulls to age-constant percentage retail yield of the steers were obtained following Yamada (1962). The highest genetic correlations (P<0.05) with PRP were 0.568, −0.532, and −0.523 with RNMS, RMD, and BIT, respectively. The best three-variable equation for predicting PRP developed from these data included RNMS, RL, and BFT (R2=0.80, P=0.0001).