Tissue distribution in pig carcasses exhibiting large differences in their degree of leanness, with special emphasis on intermuscular fat

Tissue distribution in pig carcasses was studied in pigs from seven genotype-sex groups with large variations in body composition. The animals were slaughtered at 115 kg live weight, and the left side carcass was separated into four primal cuts: belly, shoulder, loin and ham. Each primal cut was dissected into muscle, bone, skin, subcutaneous fat and intermuscular fat. The negative relationship between fat and muscle contents was much less close for intermuscular fat (R2 = 0.13-0.64) than for subcutaneous fat (R2 = 0.77-0.94), particularly in the ham and belly. The ratio of intermuscular fat to muscle decreased in a curvilinear manner with increasing muscle contents, suggesting that selection for leanness had very little effect on intermuscular fat content in modern pigs. The intermuscular fat content of the loin was a good predictor of intermuscular fat content in the whole left carcass side (R2 = 0.90). This prediction was improved with a further dissection of the belly (R2 = 0.97). The present results were obtained in a population of carcasses exhibiting very large variations in muscle content. They cannot be extended to within-breed studies of the relationships between tissue developments.