Biological tenderness differences between longissimus muscles from 3/8 and 5/8 Sahiwal
(Bos indicus) x Hereford-Angus and from Hereford-Angus (Bos taurus) were evaluated. No
significant breed cross effects were observed for carcass traits or rates of pH and temperature
decline. Loin steaks from Hereford x Angus had lower (P<.05) shear-force values and higher
(P<.05) taste panel tenderness scores at 1 and 14 d postmortem. No breed effects existed for
muscle fiber sarcomere length, muscle fiber type, muscle collagen, cathepsin enzyme activity,
or calcium-dependent protease-I and -II activity. However, calcium-dependent protease inhibitor
activity at 24 hr postmortem was greater (P<.01) in Sahiwal-crosses than for Hereford-Angus.
Less protein degradation, which causes tenderization during aging, occurred in Sahiwal-crosses
by d 14 than in Hereford-Angus at d 1 postmortem. Therefore, mechanisms involving calcium-dependent
protease and its inhibitor may be the principal factors causing tenderness differences
between Bos indicus and Bos taurus breeds.
