Abstract: Totally, 24 Simmental hybrid bulls at 18, 36, 54 and 72 months of age (6 for each age) were selected from the cattle farm of Anhui Da Ming company. The cattle were slaughtered and processed in a commercial plant. Fiber diameter, hydroxyproline content and shear force valueof the longissimus dorsi (LD) muscle were measured. The results showed that the shear force of LD muscle increased with the increase of fiber diameter and hydroxyproline content. The shear force was highly correlated with fiber diameter and hydroxyproline content, with r values of 0.833 and 0.835, respectively. The relationship between shear force and muscle fiber diameter could be described by the regression equation: y＝1.162e0.034x (R2 ＝ 0.932). The regression equation of shear force versus hydroxyproline content was y＝1.793e27.430x (R2 ＝0.947).

Key words: fiber diameter, connective tissue content, beef, tenderness