Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: April 24, 1997
Publication Date: N/A
Technical Abstract: The locus causing double-muscling (mh) in cattle is located on the proximal region of BTA2. The objective was to assess the effects of a single copy of this locus on carcass traits. Two half-sib families were developed using either a Belgian Blue x MARC III (n=219) or a Piedmontese x Angus (n=187) sire. Four microsatellite markers within the first nine centimorgans (cM) of BTA2 linkage group were used to determine the presenc or absence (grandparental origin) of the mh locus. Two additional markers, at 28 and 47 cM, were used to confirm that the locus affecting the traits was in the proximal region of BTA2. Carcass traits evaluated were rib eye area (REA; cm2), retail product yield (RP; %) USDA yield grade (YG), marbling (MA), fat thickness (FAT; cm), estimated kidney, pelvic and heart fat (KPH; %), and longissimus tenderness measured as shear force at 3 (S3) and 14 (S14) days postmortem. Data were analyzed with a model that included the fixed effects of sire and sex, and hot carcass weight as a covariate. F-statistics were obtained at 1 cM intervals to identify the position and effect of the locus. Allelic difference at the mh locus increased (P<.01) for REA and RP, and decreased MA, YG, FAT, and KPH. The effect of the mh allele (mh/+ - +/+) was 1.38, 1.47, -.9, -1.41, -.7, and -.8 residual standard deviations, respectively. Allelic differences due to the mh locus were similar for both sources (Piedmontese or Belgian Blue), supporting historical evidence that the mh locus is the same in both breeds. Individuals inheriting the mh allele had an advantage for carcass composition, but had decreased marbling scores compared to those inheriting the alternative allele. Thus, mating schemes that maximize production of mh/+ genotypes provide a viable approach for improving carcass composition.