Relationship of ultrasound speckle to marbling score in cattle

A subjective, but repeatable, scoring system was devised to quantitate ultrasound speckle in tomograms of the longissimus muscle over the 12th rib. Speckle scores in 11 of 14 groups of cattle (n = 619) were highly correlated (P less than .001) with carcass marbling score. Live animal speckle scores classified carcasses as Select or Choice with 77% accuracy. Similar accuracy was achieved as much as 148 d before slaughter by adjusting for the regression of speckle scores with days on feed. Marbling scores were not distributed normally with both positive skewness and kurtosis (P less than .001). The procedure exploited an unmodified low-cost ultrasound system; scores were estimated instantly from the monitor image. This ability to predict carcass grade at distant dates might be incorporated into a strategy to cluster feedlot cattle into outcome groups for more effective marketing. The results suggest that mathematical analysis of the ultrasound radio frequency signal or pixel map statistics might reveal parameters that could improve accuracy and precision of the method and, conceivably, could predict specific attributes of beef palatability.