Effects of Premortem Stress on Protein Expression, Steak Color, Oxidation, and Myofibrillar Fragmentation Index in the Longissimus Lumborum .

Forty castrated Holstein calves underwent an adrenocorticotropic hormone (ACTH) challenge to assess the effects of premortem stress on the longissimus lumborum (LL) following harvest. LL biopsies were collected before the challenge, at different harvest times (2, 12, 24, and 48 h; n = 10), and after 14 d aging. The expression of small heat shock proteins (SHSPs), deglycase 1 (DJ-1), and troponin were analyzed. Blood was analyzed throughout the ACTH challenge and at harvest for cortisol, oxidative stress, and complete blood count (CBC). Color and myofibrillar fragmentation index (MFI) were measured in aged samples. Unexpectedly, calves from different harvest times differed ( p = 0.05) in cortisol response. Calves were divided into two different cortisol response groups (high or low; n = 20). Statistical analysis assessed the effects of cortisol response ( n = 20), harvest time ( n = 10), and their interaction. Harvest time altered SHSPs ( p = 0.03), DJ-1 ( p = 0.002), and troponin ( p = 0.02) expression. Harvest time and cortisol response impacted steak color ( p < 0.05), and harvest time altered steak pH ( p < 0.0001). Additionally, various CBCs were changed ( p < 0.05) by harvest time. Harvest time changed ( p = 0.02) MFI. These data demonstrate that the protein expression, color, and MFI of the LL may be influenced by premortem stress.