Relationship of Fiber Diameter to Tenderness and Meatiness as Influenced by Bovine Age

Studies were made to examine various muscle fiber diameter-tenderness and muscle fiber diameter-meatiness relationships. Thirty-three Herefords of five age groups, between 6 and 90 months old, were used. Longissimus dorsi and semitendinosus muscle samples were taken from the left and right sides, aged 48-hours and 14 days. A gradual increase in fiber diameter with increasing animal age was noted for the longissimus dorsi muscle. The fiber diameter in the semitendinosus muscle increased at 6, 18, and 24 months, then leveled off. A significant dorsal, middle, and lateral “position” effect for fiber diameter was observed in the longissimus dorsi muscle. Fiber diameter decreased from the dorsal to lateral position. A slight, but non-significant, decrease in fiber diameter was noted in those samples taken 14-days post-mortem. The effect fiber diameter may have on tenderness appears to be due to the animal-age-fiber-diameter relationship. Within age groups there seems to be little relationship between fiber diameter and tenderness. Before removing the effect of animal age, fiber diameter was closely related to the longissimus dorsi area at the 12th rib and the total lean in the carcass. However, when the animal age effect was removed these relationships were non-significant.