Ultrasound, linear measurement and visual evaluation of cattle
Thirty-one slaughter steers were selected to provide variability in frame, muscle and finish. Twelve linear measurements including hip and wither height; fore and rear cannon circumference and length; and length; length of body; gaskin round mass, width circumference and shoulder width were taken on each animal. Ultrasonic measurements for ribeye area (REA) and fat thickness {FT) at the 12th rib were made with Aloka 500 and Tokyo Keiki LS 1000 instruments. A four-member panel scored each steer on a 10-point scale for trimness, muscling and frame. Carcass specific gravity (SG) was used to estimate percentage nitrogen and fat. Among linear measures, round mass and hip height were the best predictors of percent carcass nitrogen (r = .48 and .so, respectively, P < .01). Correlations of ultrasonic REA and FT with carcass REA and FT were .76 and .68 for the Aloka 500 and .65 and .77 for the Tokyo Keiki, respectively. Correlations of visual estimates with actual REA and BF measurements ranged from .72 to .84 and . 45 to . 49, respectively. Marbling score predicted by ultrasound accounted for 22% (P < .05) of the variation in carcass quality grade. Visual estimates were of little value in predicting quality grade. Simultaneous consideration of carcass FT opposite the 12th rib, REA and kidney, pelvic and heart fat percent (KPHF) accounted for 73% of the variation in carcass fat percent. Sixty percent of the variation in protein percent was explained by an equation employing FT and KPHF. These data suggest that ultrasound can predict FT more accurately than visual appraisal, but visual appraisal can more accurately predict REA.
Cattle -- Carcasses -- Grading, Ultrasonic testing
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