Abstract. Title of the paper: Variation of lean content in pig beilies of dam lines
Magnetic resonance imaging (MRI) was applied to determine the tissue composition of 157 bellies of castrated male pigs belonging to two dam-lines of the German Hybrid Pig Breeding Programme. All pigs were taken from the routine testing scheme. The analysis of carcass traits showed that pigs of line 03 were clearly leaner than those of line 01. Only in backfat thickness no significant difference could be observed. For the belly, a clear difference of 7% was found in percentage of lean. Lean content of the belly was also estimated by means of various multiple regressions using carcass traits. Percentage of lean predicted by the official equation used in German performance testing on the one hand and by means of MRI on the other hand was different particularly in line 03. A correlation of r = 0.67 and r = 0.82 between lean content determined by means of MRI and multiple regression was found for line 01 and line 03, respectively. To study the Variation between sires, variance components were estimated. Differences between sires were higher in lean content of the belly compared to backfat thickness, a trait which has been used in selection for a long time.