SHORT COMMUNICATION: Effects of low antioxidant mineral concentrations in the growing diet on marbling deposition in feedlot cattle

Objectives: This experiment investigates the effect of antioxidant mineral supplementation during a 28-d growing period on marbling deposition of feedlot steers. Materials and Methods: After a 28-d adaptation period to the feedlot, 167 SimAngus steers (272 +/- 28.2 kg, 219 +/- 15 d of age) were divided into 4 weight blocks, placed in 1 of 24 pens, and randomly assigned a dietary treatment. Dietary treatments were applied during a 28-d growing period: (1) no supplemental Cu, Mn, Zn, and Se; (2) Cu, Mn, Zn, and Se supplemented at the requirement of growing beef steers; and (3) Cu, Mn, Zn, and Se supplemented at twice the requirement. Plasma was collected after the growing phase to quantify nonesterified fatty acid and thiobarbituric acid reactive substance concentrations. Afterward, steers were offered a common finishing diet until being removed from the experiment for slaughter at a similar backfat thickness. Statistical analyses used a mixed model in SAS, considering the fixed effect of treatment and the random effect of block. Results and Discussion: There were no treatment differences (P > 0.35) for measures of feedlot performance, carcass, and blood metabolite. With the exception of Cu, it is possible adequate mineral concentrations supplied by the basal diet caused a lack of treatment differences. Additionally, liver and body mineral stores may not have been depleted during the 28 d of the experimental intervention. Implications and Applications: Future research is needed to further investigate the effects of dietary antioxidant mineral level on marbling deposition of feedlot steers.