|Hamlin Keith E, - TEXAS TECH UNIVERSITY|
|Green Ronnie D, - TEXAS TECH UNIVERSITY|
|Dikeman Michael, - KANSAS STATE UNIVERSITY|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 7, 1994
Publication Date: N/A
Interpretive Summary: The use of ultrasonics as a method of predicting retail yield measures looks promising and warrants further investigation. Areas of study need to include: (1) determination of proper adjustments of retail yield measures for comparisons (i.e., age or weight adjustments); (2) determination of alternative site measures to serve as improved estimators of retail lean yield; and (3) determination if these same measures can effectively be used with breeding cattle to predict progeny performance. These data indicate that ultrasound can be used to predict retail product percentage in the live animal. This type of information should be useful in the beef industry's desire to move towards some type of value-based marketing system requiring an objective estimate of carcass merit in the live animal. Progress can also be made towards the development of carcass merit EPD's, which will improve the capability of selecting breeding animals with greater propensity for producing progeny with more desirable carcass attributes.
Technical Abstract: Feedlot steers (n=180) representing 11 sire-breed groups were ultrasonically measured for fat thickness (FTU) and longissimus muscle area (LUM) at two 60-d intervals during the feeding period and four 21-d intervals corresponding to serial slaughter dates to predict carcass retail yield and quality grade parameters. Two fat trim levels, 8 and 0 mm, were used to calculate percentage trimmable fat (FAT8P and FATOP) and retail product percentage (RPD8P and RPDOP) for each carcass. Regression techniques were utilized to evaluate best fit equations that explained variation in retail product components. When FAT8P, FATOP, RPD8P and RPDOP were regressed on USDA yield grade (YG), R-squared values ranged from 75 to 76% (P<.0001). Comparatively, when live animal predictors of YG components (FTU, LMU and final live weight) were used as the independent variables, equations involving retail yield levels had R- squared values of 61 to 65% (P<.01). Equations using final FTU as the independent variable explained 58 to 64% (P<.0001) of the variation of FAT8P, FATOP, RPD8P and RPDOP. Equations with FTU, LMU and either WT, AGE, MARB and QG resulted in similar R-squared values as those with only FTU, indicating the strong influence of fat on retail yields. These results indicate ultrasonic prediction of retail product percentage to be about 10% less effective than that of carcass measures.