EVALUATION OF DIFFERENT RULER AND ULTRASONIC BACKFAT MEASUREMENTS AS INDICES OF COMMERCIAL AND LEAN YIELD OF HOG CARCASSES FOR COMMERCIAL GRADING PURPOSES

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Abstract
A total of 3807 carcasses (1939 barrows and 1868 gilts) ranging in warm carcass weights from 44.9 to 116.2 kg were obtained by a stratified gusta sampling procedure from three important pork-producing regions of Canada. Backfat thickness at different locations was measured using a ruler on the exposed surface of the warm split carcass and ultrasonically 5 cm laterally from the exposed surface. The value, in terms of residual standard error, of single, pairs or sums of backfat measurements in describing the relationships between backfat thickness and commercial and lean yield was examined. Generally, the use of ultrasonic fat measurements over that of ruler fat measurements resulted in smaller residual standard error values. Of the four ruler fat measurements, whether considered singly or as sums of two measurements, the single measurement of backfat thickness over the lumbar region (gluteus mediums muscle) provided the smallest residual standard error value. Sex, region of slaughter and weight of warm carcass influenced (P < 0.01) the relationships between backfat thickness and yield.