Genetic parameters for characteristics of pork bellies

Belly characteristics including predicted fat percentage of the belly (FATPC), joint area of the rib bone and muscle (RBMA), between muscle fat area (BMFA), subcutaneous fat area (SFA) were recorded on 2,403 pigs along with fat depth at the P2 site (P2). These traits were derived from image analysis of the anterior side of pork bellies. Data were available for juvenile insulin-like growth factor-I (18,398 records), lifetime growth rate (35,074 records), backfat (35,404 records) and muscle depth (34,869 records). Heritability estimates ranged from 0.23 to 0.34 and litter effect estimates were 0.07 or lower for belly traits. Genetic correlations between FATPC and individual fat measurements were high (range: 0.71 to 0.85). Genetic correlations between BMFA and subcutaneous fat measurements differed from unity (range: 0.47 to 0.63). Only muscle depth had a significant genetic correlation with RBMA of 0.39. Genetic correlations between belly and performance traits show that selection based on reduced juvenile-IGF1, backfat and muscle depth will reduce overall fat levels in the belly. However, genetic improvement of individual muscles requires specific measurements and practical pig breeding programs require measurements that can be routinely recorded on the slaughter line.