Use Of Serial Real-Time Ultrasonic Measurements To Evaluate Relative Changes In Fat Thickness, Ribeye Area, And Percent Intramuscular Fat Of Yearling Bulls And Heifers

Date of Graduation

Spring 2002


Master of Natural and Applied Science in Agriculture


College of Agriculture

Committee Chair

Thomas Perkins


With the advent of value-based marketing and an increased consumer demand for a leaner and more consistent product, all aspects of the livestock industry have become more concerned with carcass traits. The best way to measure these carcass traits today is through the use of real-time ultrasound imaging. Real-time imaging can capture and measure the images of fat thickness, ribeye area, and percent intramuscular fat on a live animal. Evaluating changes in ultrasonic measures over the course of a feeding period would allow for the development of prediction equations for fat thickness, ribeye area, and percent intramuscular fat and to determine if the optimum time to scan both bulls and heifers is at approximately one year of age. Ultrasound was used to measure changes in fat thickness (FTU), longissimus muscle area (REAU), and percent intramuscular fat (PFU) four different times on four Black Angus sired bulls and four Black Angus sired heifers. Live animal measures of body weight were taken at the time of each scan session. The prediction equations that were derived from the data show that the ultrasonic measurements and weight measurements taken on day 35 (the second measurements) are the best predictors of final measurements when the cost and time of ultrasounding is also considered. Thier R² values are only 0.00 to 0.07 less than those equations derived from three serial measurements. Prediction equations developed from the the first three ultrasonic measurements were characterized by R² values (0.70-0.93), however, the best fit equations derived from day 35 measurements had similar R² values (0.65-0.93). In conclusion, selection using yearling ultrasound measurements of breeding attle should result in predictable genetic improvement for carcass characteristics.

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