It is odd how all the vendors in the bull sales are required to do ultrasound scans for eye muscle (LMA = longissimus dorsi muscle area), since the readings on bulls aged 24 months are almost all approximately 100 to 120 cm2, and the inherent accuracy of the machine + operator is within 10% of the quoted figure, which means that all the readings are the same, within the limits of accuracy, ie 110 plus or minus 11.
In a study of 30 cattle scanned by 8 operators Robinson et al 1992, Journal of Animal Science state' Correlations with carcass data averaged .92 for rump fat, .90 for rib fat, and .87 (ie-with 87 to 92% accuracy) for EMA. Residual Standard Deviation averaged .81 mm, .88 mm, and 5.1 cm2(ie EMA was within 5 cm2 either side of the figure in 2/3 of cases). A very experienced sonographer can measure EMA only marginally less accurately than it can be measured on the carcass.'
Is the net result that we are all paying money for nothing?
Adding to the complexity of this issue is the fact that no commercial producer gets paid for the eye muscle in their draft of steers or heifers at the meatworks. They are paid for kilograms of beef in the carcase by weight and number, so all they want in a bull is one that produces:
1. more calves
2. heavier calves.
