Measurement of belly composition variability in pigs by in vivo computed tomographic scanning

The belly region composition of a representative commercial pig sample of 130 castrates was examined by in vivo spiral computed tomographic (CT) scanning. The lean meat percentage, the muscle/fat tissue ratio within the total body and separately within the bacon part were estimated by image analysis. The lean meat content of the total body was determined by the EU reference method. A correlation of r = 0.97 was found between lean meat content of the total body determined by CT estimation and the slaughtering results. The pigs were divided into seven groups on the basis of their lean meat content. The muscle percentage of the bacon part was 26% and 67%, respectively, in the two groups representing the two extremes of lean meat percentage (36% and 67%, respectively). The total volume of the bacon part was relatively constant (8.6 +/- 1 dm3) in the groups representing different lean meat categories. At the same time, the fat tissue volume of the bacon part was considerably higher while its muscle tissue volume was markedly lower in the group of the lowest than in that of the highest lean meat content (6.6 vs. 2.5 dm3 and 2.4 vs. 5.5 dm3, respectively). To describe changes in the tissue composition of the bacon part during fattening, 10 castrates were scanned repeatedly at 70, 90 and 110 kg of liveweight. A linear regression model was developed to characterise the continuous decrease observed in the muscle/fat ratio within the bacon part due to increasing liveweight.