Predicting carcass composition of beef cattle using ultrasound technology.

We evaluated 20 slaughtered cattle with ultrasound before hide removal to predict fat thickness and ribeye area at the 12th rib for possible use in carcass composition prediction. Carcasses were fabricated into boneless subprimals that were trimmed progressively from 2.54 to 1.27 to .64 cm maximum fat trim levels. Stepwise regression was used to indicate the relative importance of variables in a model designed to estimate the percentage of boneless subprimals from the carcass at different external fat trim levels. Variables included those obtained on the slaughter floor (ultrasound fat thickness and ribeye area; estimated percentage of kidney, pelvic, and heart [KPH] fat; and warm carcass weight) and those obtained from carcasses following 24 h in the chill cooler (actual fat thickness, actual ribeye area, estimated percentage of KPH fat, warm carcass weight, and marbling score). At all different subprimal trim levels, percentage KPH was the first variable to enter the model. In the models using measures taken on the slaughter floor, ultrasound fat thickness was the only other variable to enter the model. Ultrasound fat thickness increased R2 and decreased residual standard deviation (RSD) in models predicting subprimals at 2.54-cm maximum fat trim; however, at 1.27- and .64-cm trim levels, R2 and RSD increased. Models using the same two variables (except actual fat instead of ultrasound) in the cooler were similar to those using data from the slaughter floor. However, as more cooler measurement variables entered the models, R2 increased and RSD decreased, explaining a greater amount of the variation in the equation. Ultrasonic evaluation on the slaughter floor may be of limited application compared with the greater accuracy found in chilled carcass assessment.

Using ultrasound technology to predict pork carcass composition.

Twenty market hogs were evaluated with real-time ultrasound both before and after slaughter. Fat measures (n = 9) were taken at various body locations along with the longissimus muscle area measurement at the 10th rib. After live ultrasound, the hogs were slaughtered and the unsplit carcasses were measured with ultrasound at the same live ultrasound locations. After chilling, carcass measures were taken at the same locations using a backfat probe for fat measures and a loin eye dot grid for measuring the longissimus muscle area. One side of each carcass was fabricated into the four lean cuts, which then were expressed as a percentage of the side weight. The most appropriate prediction equation found was a two-variable equation (fat thickness at the anterior tip of gluteus medius and longissimus muscle area) with a R2 of .83 and a RSD value of 1.67. This prediction equation was verified on a different sample of 20 market hogs; actual vs predicted four lean cuts revealed that the prediction equation had a R2 of .63 and a RSD value of 2.04. Although some accuracy and precision was lost when this live animal prediction equation was incorporated in market hog evaluation, this equation offers producers an objective mechanism for identifying carcass merit in live hogs.

Evaluation of live and carcass techniques for predicting beef carcass composition.

Fifty beef animals varying in size, age and composition were used to determine the most accurate methods for determining beef composition. Separable and chemical composition of the 9-10-11th rib section and measurements of subcutaneous fat thickness were the most useful for explaining observed variability in carcass composition. For predicting percentage fat in fed steers, composition of the 9-10-11th rib section was the most accurate [coefficient of determination (R(2) 0·85)]. The 9-10-11th rib section was the most accurate and precise technique identified in this study to estimate beef carcass composition across and within all age classes. Specific gravity accounted for 68% of the variation in percentage of carcass fat across all age classes combined; however, specific gravity did not account for a significant portion of the variation within each age class. Deuterium oxide dilution was able to account for 77% of the variation in chemical fat percentage across all age classes combined; however, deuterium oxide dilution was not as effective in accounting for the observed variation in fat percentage within each age class. Ultrasound was found to be an accurate live measure of chemical fat percentage within all age classes combined.