Backfat and Loin Eye Area and Their Relationship to Performance of Boars Tested to Heavier Weights2

Data from four tests involving 360 boars (Duroc, Hampshire and Yorkshire) tested at the University of Missouri-Columbia Swine Test Station were analyzed to determine backfat (BF) and loin eye area (LEA) at weights of 104.3 and 131.5 kg. In addition, the relationship of BF and LEA to average daily gain (ADG) and feed efficiency (F/G) was examined and adjustments were determined for predicting BF and LEA at a standard weight. Average BF and LEA at 104.3 and 131.5 kg body weight were 1.94 cm and 36.7 cm2 and 2.61 cm and ‘42.0 cm2 , respectively. Backfat was noted to increase .024 cm/kg increase in body weight (34.5%) as weight increased from 104.3 to 131.5 kg (26.1%) whereas LEA increased 14.4% (.185 cm /kg). Differences in breed BF means were not significant (P>.05) at 104.3 and 131.5 kg. Correlations of BF and LEA at 104.3 kg with BF and LEA, respectively at 131.5 kg were low. Correlations of BF and LEA with ADG and F/G were low and erratic. The linear regression coefficient for BF (.024 cm/kg) on live weight was similar to the National Swine Inprovement Federation (NSIF) value; however, the coefficient for LEA (.185 cm2/kg) was smaller than the NSIF value.