Use of live ultrasound, weight and linear measurements to predict carcass composition of young beef bulls

Abstract

Pre-slaughter ultrasound and whole side dissection data from 47 crossbred bulls were used to assess (1) the relative value of six previously published equations based on live animal measurements, (2) the value of alternative pre-slaughter measurements, and (3) the value of alternative ultrasound probes as predictors of whole side lean meat yield. Analysis of absolute bias-corrected residuals indicated that all six previously published equations predicted whole side lean meat yield with similar accuracy (P = 0.62), but analysis of absolute rank residuals indicated that an equation originally based on carcass measurements tended (P = 0.17) to rank bulls less precisely than five ultrasound-based equations. Breed composition, age, liveweight, hip width, heart girth, and round muscle depths did not contribute to new lean meat yield prediction equations (P > 0.10), but height, 12th/13th rib body wall, rump fat, and gluteus medius muscle depths and marbling score did (P < 0.10). However, examination of absolute residuals and absolute rank residuals indicated that accuracy (P = 0.55) and precision (P = 0.64) did not improve significantly compared to equations based only on height, rib fat and longissimus muscle size. Similarly, analysis of absolute residuals and absolute rank residuals indicated that fat and longissimus muscle depth measurements collected with a short probe predicted whole side lean meat yield as accurately and precisely as measurements collected with a long probe. Results indicated that (1) equations based on live measurements may provide more precise predictions of lean meat yield than equations derived from carcass measurements, (2) supplementing ultrasonic rib fat and longissimus muscle measurements with additional ultrasound measurements did not improve the accuracy or precision of lean meat yield prediction, and (3) lean meat yield of yearling bulls can be accurately predicted using fat and longissimus muscle depth measurements collected with a short probe. Key words: Ultrasound, beef bulls, carcass composition, prediction models