The use of ultrasound to predict fatness in lambs

Ultrasonic measurement of fat depth, over the eye muscle of lambs was found to be highly correlated with measurement on the carcass in two experiments with coefficients of 0·93 and 0·95. Linear regression analysis showed that over a limited range of fatness the slope (regression coefficient) approached unity and the residual standard deviation of the regression was approximately ± 1 mm. However, the slope of the line was greater than unity over a wider range of fatness and the accuracy decreased. The instrument used was more useful for predicting fat depth than carcass fat percentage, explaining less of the variation in the latter variable than the former. It is apparent that further investigation of the instrument over a wide range of lambs is needed to clarify the implications for selection schemes or, alternatively, technology adopted which overcomes the underestimation found in fat animals.