PREDICTION OF LEAN YIELD IN CULL SOWS

Data from 204 sows were used to predict percentage carcass lean yield and lean weight. Backfat thickness (probe fat) and muscle depth (probe lean) were measured with an electronic probe. Fat thickness was also measured by ruler at the midline at maximum fat depth over the lumbar vertebrae (maximum fat), fat depth at the last rib (last-rib fat), and fat depth between the 3rd- and 4th-last ribs (fat depth 3-4). Fat depth over maximum loin-muscle depth (loin fat 1), maximum fat depth over loin muscle (loin fat 2), maximum loin depth (loin lean 1) and maximum loin width (loin lean 2) were measured on loin cross section. On the warm carcass, the prediction accuracy of percentage lean yield was highest for probe fat (R2 = 0.77), whereas probe lean had the lowest coefficient of determination (R2 = 0.01). Among the ruler measurements, maximum fat was associated with the most accurate prediction of percentage lean yield (R2 = 0.71). Among cross-section measurements, loin fat 2 was the most accurate predictor of percentage lean yield (R2 = 0.78). For predicting lean weight in the carcass, carcass weight gave the highest coefficient of determination (R2 = 0.82) of any single measurement, but addition of probe fat to the equation improved R2 by 11% and reduced the RSD from 3.16 to 2.00. A single measurement by probe (probe fat) or ruler (maximum fat) was concluded to be sufficient to accurately predict percentage lean yield in sow carcasses.