Machine effects on accuracy of ultrasonic prediction of backfat and ribeye area in beef bulls, steers and heifers

Abstract

Pre-slaughter ultrasound and carcass measurements of ribeye area (REA) and backfat (FAT) were recorded on composite beef bulls (n = 60), heifers (n = 60) and steers (n = 60). Breed composition of the composite was: 0.44 British (Hereford, Angus and Shorthorn) 0.25 Charolais, 0.25 Simmental and 0.06 Limousin. The Aloka SSD-1100 (AL) and the Tokyo Keiki CS 3000 (TK) ultrasound machines were compared by evaluating the difference between ultrasound and carcass measurements (bias), and the standard error of prediction (SEP). AL under-predicted REA in all three sexes while TK overpredicted heifers and steers and underpredicted bulls. Both machines were similar in accuracy among bulls for REA. For FAT AL underpredicted all three sexes while TK underpredicted heifers and had very small bias for bulls and steers. SEP for FAT were similar for both machines. Both machines underpredicted REA in larger muscled cattle and overpredicted in smaller-muscled cattle. Both machines also underpredicted FAT in fatter animals and overpredicted FAT in leaner animals. Machines were similar in accuracy among cattle with larger REA but differed significantly (P < 0.05) among smaller-muscled cattle. Machines were comparable in accuracy among animals of all FAT sizes. This study demonstrates that there is an important relationship between machine and the size and depth of muscle and backfat, respectively, and consequently between machine and sex, in accuracy of ultrasound prediction. Key words: Beef cattle, ultrasound, accuracy, back fat, ribeye area