|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: November 15, 2002
Publication Date: February 11, 2003
Citation: Greiner, S.P., Rouse, G.H., Wilson, D.E., Cundiff, L.V., Wheeler, T.L. 2003. Accuracy of predicting weight and percentage of beef carcass retail product using ultrasound and live animal measures. Journal of Animal Science. 81:466-473. Interpretive Summary: Results from this research indicate live animal prediction equations developed from ultrasonic measurements are similar in their predictive power and accuracy for weight and percentage of beef carcass retail product when compared to equations developed from carcass measurements. Ultrasonic measurement of rump fat and body wall thickness, two measurements that are easy to obtain on the live animal, added to the predictive capability of traditional ultrasound measures of 12th-rib fat and longissimus area. Application of live animal prediction models that successfully predict carcass composition in slaughter progeny and breeding animals will allow for rapid genetic progress and enable producers to be competitive in a value-based marketing system.
Technical Abstract: Five hundred thirty-four steers were evaluated over a two year period to develop and validate prediction equations for estimating carcass composition from live animal ultrasound measurements and to compare these equations with those developed from carcass measurements. Within 5 d prior to slaughter, steers were ultrasonically measured for 12th-rib fat (UFAT), longissimus area (UREA), rump fat thickness (URPFAT), and body wall thickness (UBDWALL). Carcasses were fabricated to determine boneless, totally trimmed retail product weight (KGRPRD) and percentage (PRPRD). Data from steers born in year 1 (n = 282) were used to develop prediction equations using stepwise regression. Final models using live animal variables included live weight (FWT), UFAT, UREA, and URPFAT for KGRPRD(R**2 = 0.83) and UFAT, URPFAT, UREA, FWT, and UBDWALL for PRPRD(R**2 = 0.67). Equations developed from USDA yield grade variables resulted in R**2 values of 0.87 and 0.68 for KGRPRD and PRPRD, respectively. When these equations were applied to steers born in year 2 (n = 252), correlations between values predicted from live animal models and actual carcass values were 0.92 for KGRPRD, and ranged from 0.73 to 0.76 for PRPRD. Similar correlations were found for equations developed from carcass measures r = 0.94 for KGRPRD and 0.81 for PRPRD. Both live animal and carcass equations overestimated (P < -0.01) actual KGRPRD and PRPRD. Regression of actual values on predicted values revealed a similar fit for equations developed from live animal and carcass measures. This research indicates that composition prediction equations developed from live animal and ultrasound measurements can be useful to estimate carcass composition.