The effect of altered growth rates on the calpain proteolytic system and meat tenderness in cattle

The present study was conducted to determine the effects of growth pattern on the calpain system and meat tenderization. Twenty-four Friesian calves were randomly allocated to three treatment groups: FAST (fast growth rate), SLOW (severely restricted growth rate) and ALTER (restricted growth for 30 days followed by fast growth rate). Four animals from each group were slaughtered on day 32 or 45 after altering the growth rates. Samples of M. longissimus dorsi were rapidly frozen at slaughter for protein analysis by Western blotting. Restricted growth reduced the immunoreactivity of a calpastatin band (135 kDa) measured at 24 h postmortem. Immunoreactivity associated with the large subunit of μ- or m-calpain appeared to be unaffected by growth patterns. Shear force measurements taken after 14 days of conditioning were positively related to 135 kDa calpastatin at 24 h postmortem. In this study there was no clear relationship between shear force and growth pattern.