A comparison of three ultrasonic machines (Danscan, AIDD (NZ) and Body Composition Meter) and subjective fat and conformation scores for predicting chemical composition of live sheep

Abstract

SUMMARY: Ultrasonically measured backfat depths and subjective fat and conformation scores taken on 123 Romney ewes were related to the chemical composition of the carcass in trial 1. Fat depths at one position over the eye muscle, determined using ultrasonic machines with a single probe, were similar to the best judge's fat scores at predicting carcass composition after adjustment for pre-slaughter live weight. Fat depths measured from a two-dimensional scan (Danscan) did not predict carcass composition as well as most of the judges' fat scores. Judges' conformation scores failed to improve the prediction of composition after adjustment for live weight and fat score.In trial 2, two ultrasonic machines of the single probe type provided accurate measure of carcass fat depths on both full fleeced and shorn sheep. Ultrasonically measured fat depths would appear to be a useful method for selecting lean breeding stock and for training inexperienced stock judgesto assess fatness of sheep.