Abstract
Increased use of beef semen by dairy operations has increased numbers of beef x dairy crossed cattlein feedlots. The current study evaluated the predictability of genetic marbling scores (GMS) on
carcass marbling scores (MS) in beef x dairy steers and the effect of days on feed on MS. Tissue
samples from beef x dairy steers (N = 363) were analyzed using the Igenity® BeefxDairy genomic
test. Steers were grouped by GMS into three groups: low potential (GMS = 4-5; n = 141), medium
potential (GMS = 6; n = 162), and high potential (GMS = 7-8; n = 60). Cattle were randomly assigned
to one of 3 harvest groups, each containing equal distributions of low, medium, and high potential
animals. The ‘normal’ harvest date (day 0) based on finish weight projections was determined by an
experienced beef feedlot operator; a ‘short-fed’ harvest date was 3 weeks before and ‘long-fed’ was 3
weeks after. Cattle were harvested at a commercial packing plant where carcass results were
collected. Data were analyzed using an ANCOVA mixed model with harvest date, marbling group,
and their interactions as fixed effects, and GMS as a covariate. Marbling score observed was
significantly affected by marbling group (P = 0.011) and harvest date (P < 0.001) main effects.
Feeding medium and high potential animals longer increased MS. Low potential animals did not
significantly increase MS with more days on feed. These results indicate that GMS can be used as a
valuable tool for producers to predict MS and make management decisions.