Bovine sire selection based on maintenance energy affects muscle fiber type and meat color of F₁ progeny

A total of 42 F₁ Red Angus progeny from sires divergent in maintenance energy (MEM) EPD were analyzed to determine whether selecting for sire ME_M would alter end-product meat quality. Data from animals were grouped based on the divergence of the ME_M EPD of their sire from the Red Angus Associationreported breed average and defined as either high or low, the assumption being that high-ME_M cattle are less efficient because their maintenance requirements represent a larger proportion of their dietary intake. Steer progeny (n = 7) from the high group produced bottom round steaks with a greater a&z.ast; (redness) color value (P = 0.02) after 5 d in a simulated retail display when compared with bottom round steaks from the low group (n = 18). Bottom round steaks from the high group had a greater b&z.ast; (yellowness) color value at d 1 (P = 0.03) and d 5 (P = 0.01) of retail display. Samples from the biceps femoris were taken at 12 mo (from both steers and heifers) and 15 mo (from steers only) of age for fiber type proportion analysis. At 12 mo of age, steers from the low group had more type I fibers (P = 0.02), whereas steers from the high group had more type IIb fibers (P = 0.01). Furthermore, samples from steers in the low group at 15 mo had more type I fibers (P = 0.02), and steers from the high group maintained more type IIb fibers (P = 0.02). No changes in fiber type proportions were observed between the high- and low-ME_M EPD heifers (n = 17). Relative mRNA abundance of genes involved in the synthesis, storage, and breakdown of glycogen were analyzed as a variable important for meat quality, but no statistical differences were observed. At 12 mo age, glycogenin (glyc) was negatively correlated with the proportion of type IIa fibers (r = -0.32 and P = 0.12) as well as with the proportion of type IIb fibers (r = -0.42 and P = 0.03) in the biceps femoris of the steers. In samples taken from the biceps femoris at 15 mo age, glyc was negatively correlated with the proportion of type IIa fibers (r = -0.42 and P = 0.03) in the steers. This indicates that relative mRNA expression of glyc may serve as a marker of muscle glycogen storage capacity in steers. Thus, selection for efficient Red Angus beef cattle based on sire ME_M EPD does not adversely affect meat quality in F₁ progeny, based on the variables assessed in this study. Furthermore, selection for progeny from low-ME_M EPD sires may improve fresh meat quality within Red Angus beef cattle.