ABSTRACT
Eighteen Nellore steers were classified as either excitable (high index) or calm (low index) temperament, and high or low WB Shear Force (SF) in Longissimus lumborum at 16â¯days postmortem, with a subset assigned to four groups: HTHS-high temperament and SF (nâ¯=â¯5); HTLS-high temperament and low SF (nâ¯=â¯4); LTHS-low temperament and high SF (nâ¯=â¯4); LTLS-low temperament and SF (nâ¯=â¯5). Only the second calpastatin peak was detected at 48â¯h in the all samples, and the calpastatin activity only differed (Pâ¯<â¯.05) between shear force groups. High WBSF groups had greater expression of CAST gene (Pâ¯<â¯.05) in the high and low temperament. Western blots showed a calpastatin fragmentation pattern very particular to each group with high molecular weight bands present in the HTHS. Temperament was not a determinant factor in postmortem proteolysis variation. However, greater WBSF aged meat from high temperament animals had greater calpastatin activity and less calpastatin fragments formed during the postmortem period analyzed.