Ultrasonic estimates of muscle and fat thickness in live cattle as predictors of carcass yield

The purposes of this study were to determine the relationships between both linear and ultrasonic measurements in84 live beef steers and carcass composition. Fat thickness over the longissimus dorsimeasured ultrasonically was positively related to retail cuts weight but negatively related to retail cuts percent, accounting for about 35 percent of the variance. Biceps femoris muscle depths tended to have higher associations with cutout measures than did longissimus dorsior infraspinatus muscle depths. Live weight, which was used in all multiple regression equations, generally accounted for a larger amount of the variance in carcass composition than any other single measurement. Estimated round mass (alinear measurement, beginning at the tail, then encircling the leg and continuing to the dorsal midline between the hooks) and live weight were of significant value in pre 2 dieting round separable muscle weights (R² =0.58). Live Weight and either estimated round mass or Biceps femoris muscle depth were the most accurate predictors of round separable muscle weight. Biceps femoris depth and live weight were the most effective estimators of retail cuts weight. Fat thickness over the longissimus dorsiand live weight were the only variables which had a significant effect in predicting percent retail cuts. In conclusion, these predictions of carcass composition were sufficiently accurate and valid for steers, but should not be used on heifers or bulls without further testing.