Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1999
Publication Date: N/A
Technical Abstract: The locus causing muscle hypertrophy (mh) has been previously assessed for growth and carcass traits. The objective was to identify other quantitative trait loci (QTL) in two families segregating the mh allele. Families were developed from a Belgian Blue x MARC III (n=246) or a Piedmontese x Angus (n=209) sire. Traits analyzed were birth (BW; kg) and yearling weight (YW; kg); hot carcass weight (HCW; kg); fat depth (FD; cm); marbling score (MA) rib eye area (REA; cm2); estimated kidney, pelvic, and heart fat (KPH; %); yield grade (YG); retail product yield (RP; %). Meat tenderness was measured as Warner-Bratzler shear force at 3 (WB3) and 14 (WB14) d postmortem. The effect of the mh locus was removed using information based on six flanking markers. To identify putative regions harboring QTL associated with RP and FD, selective genotyping was done on 92 animals from the extremes of the phenotypic distribution from both families, using a total of 150 informative genetic markers. Regions in which selective genotyping indicated the presence of QTL were evaluated further by genotyping the entire population and additional markers. In the Belgian Blue cross family, a significant QTL (P<.00005; expected number of false positives=.05) for BW and YW was identified on chromosome 6 and suggestive QTL (P<.002; expected number of false positives=1) were identified for REA and HCW, and for MA on chromosomes 17 and 27. In the Piedmontese cross family, a suggestive QTL was identified for FD, RP, and YG on chromosome 5; and for WB3 and WB14 on chromosome 29. Interactions suggesting the presence of QTL were observed between the mh locus and chromosome 5 for WB14; and the mh locus with chromosome 14 for FD. Thus, other loci influencing carcass traits have been detected in families segregating the mh locus.