Effects of the F94L myostatin gene mutation in beef x dairy crossed cattle on strip loin steak dimensionality, shear force, and sensory attributes

Carcasses (n = 115) from steers resulting from the mating of four Limousin x Angus sires heterozygous for the F94L myostatin mutation to Jersey, Jersey x Holstein, and Holstein dams were utilized to evaluate the effects of one copy of the F94L allele on strip loin dimensionality, Warner-Bratzler shear force and slice shear force, and sensory panel ratings. In phase I of a two-phase study, 57 carcasses from two sires were utilized to obtain samples of longissimus dorsi (LD), psoas major (PM), gluteus medsius (GM), semitendinosus (ST), serratus ventralis, triceps brachii, and biceps femori muscles, which were vacuum packaged, aged until 10 d postmortem, and frozen. Frozen strip loins were cut into 14, 2.5-cm-thick steaks each, and individual strip loin steaks were imaged at a fixed height on a gridded background and processed through image analysis software. In phase II, to obtain a greater power of test for LD palatability attributes, 58 additional carcasses from three sires were utilized to obtain LD samples only for sensory panel and shear force analysis. Cooked steak sensory attributes evaluated by trained panelists were tenderness, juiciness, beef flavor, browned flavor, roasted flavor, umami flavor, metallic flavor, fat-like flavor, buttery flavor, sour flavor, oxidized flavor, and liver-like flavor. In strip loin steaks from carcasses with one F94L allele, LD muscle area was larger in steaks 4, 5, 7, 8, and 9, and steaks 1, 6, 7, and 9 were less angular than those from carcasses with no F94L allele (P < 0.05). Of the seven muscles observed, there were no shear force differences between F94L genotypes (P > 0.20). F94L genotype did not affect sensory panel ratings of LD and GM steaks (P > 0.07). Cooked ST steaks from carcasses with one F94L rated lower in fat-like flavor compared to those from carcasses with no F94L allele (P = 0.035). Cooked PM steaks from carcasses with one F94L allele rated lower in juiciness, fat-like flavor, buttery flavor, and umami flavor compared to those with no copies of the F94L (P < 0.04). In summary, one copy of the F94L allele utilized in beef x dairy cross steers improved strip loin steak dimensionality, did not affect cooked steak tenderness across seven muscles, and decreased fat-associated flavors in the PM and ST. The use of F94L homozygous terminal beef sires would be an easily implemented strategy for dairy producers to improve steak portion size and shape in carcasses from nonreplacement calves.