|Greiner, Scott - VIRGINIA TECH UNIV.|
|Rouse, Gerald - IOWA STATE UNIV.|
|Wilson, Darrell - IOWA STATE UNIV.|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2003
Publication Date: July 1, 2003
Citation: Greiner, S.P., Rouse, G.H., Wilson, D.E., Cundiff, L.V., Wheeler, T.L. 2003. Prediction of retail product weight and percentage using real-time ultrasound and carcass measurements in beef cattle. Journal of Animal Science. 81:1736-1742. Interpretive Summary: This research indicates that live animal ultrasound measurements are useful predictors of weight and percentage of retail product yield. Alternative measurements of rump fat and body wall thickness are made possible with ultrasound technology, which enhances the predictive capability of live animal-based equations for retail yield. Rump fat improved prediction equations for percentage of retail product when used along with live weight and traditional ultrasonic measurements of 12th-rib fat thickness and longissimus area. The relative ease with which this measurement may be taken further justifies its inclusion. Although body wall thickness was found to be a significant variable in equations for retail yield, little additional variation was explained. Further investigation and refinement of this measurement are needed. Live animal prediction equations using ultrasound measurements will enhance genetic evaluation programs for carcass traits.
Technical Abstract: Data from five hundred thirty-four steers representing six sire breed groups were used to develop live animal ultrasound prediction equations for weight and percentage of retail product. Steers were ultrasonically measured for 12th-rib fat thickness (UFAT), rump fat thickness (URPFAT), longissimus area (UREA), and body wall thickness (UBDWALL) within 5 d prior to slaughter. Carcass measurements included in USDA yield grade (YG) and quality grade calculation were obtained. Carcasses were fabricated into boneless, totally trimmed retail product. Regression equations to predict weight (KGRPRD) and percentage (PRPRD) of retail product were developed using either live animal or carcass traits as independent variables. Most of the variation in KGRPRD was accounted for by live weight (FWT) and carcass weight with R**2 values of 0.66 and 0.69, respectively. Fat measurements accounted for the largest portion of the variation in PRPRD when used as single predictors (R**2 = 0.54, 0.44, 0.23, and 0.54 for UFAT, URPFAT, UBDWALL, and carcass fat, respectively. Final models (P < 0.10) using live animal variables included FWT, UFAT, UREA, and URPFAT for KGRPRD (R**2 = 0.84) and UFAT, URPFAT, UREA, UBDWALL, and FWT for PRPRD (R**2 = 0.61). Comparatively, equations using YG variables resulted in R**2 values of 0.86 and 0.65 for KGRPRD and PRPRD, respectively. These results indicate that live animal equations using ultrasound measurements are similar in accuracy to carcass measurements for predicting beef carcass composition.