Two speed congenic panels were created, the first comprehensively dissected MMU2 while the second isolated QTL on MMU1, 5, 8, 9, 11 and 17 (Table 1). The MMU2 panel consisted of eight congenic strains developed by introgressing four overlapping donor regions onto both B6 and HG genetic backgrounds (Table 1). Single donor regions bred onto an HG background were created to isolate the remaining QTL on MMU1, 5, 8, 9, 11 and 17. Implementation of a speed congenic approach using marker-assisted breeding with 79 genome-wide microsatellite markers accelerated production of all strains [5,6] (Additional File 1 and Figure 1). Strain abbreviations and genomic region isolated by each strain are listed in Table 1. In addition to both congenic panels, two control strains homozygous B6 (B6.CASTC; B6C) or HG (HG.CASTC; HGC) for all genome-wide markers genotyped were developed from the same cross (see Methods) and served as the basis for strain comparisons. After stabilizing each congenic, 12 of 14 were phenotypically characterized for growth and adiposity. The HG2D and HG5 strains were not characterized due to reproductive problems. The recombinant end points for all strains were refined using microsatellite markers flanking each donor region (Additional File 2).