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279 Effects of pre-mortem stress on heat shock protein expression in the longissimus lumborum following harvest


 Despite similar production practices, meat products from beef cattle exhibit undesirable variation in tenderness and stability of flavor and color. The objective of this study was to determine whether pre-mortem stress impacts expression of heat shock proteins (HSP) in the skeletal muscle following harvest. In this study, 40 Holstein steers underwent a 6 h adrenocorticotropic hormone (ACTH) challenge designed to emulate pre-mortem stress prior to harvest. Skeletal muscle biopsies from the longissimus lumborum were taken prior to the ACTH challenge. During the challenge, complete blood counts (CBC) were collected every 2 h and serum cortisol every 0.5 h from -2 to 6 h of the ACTH challenge. Following the 6 h ACTH challenge, skeletal muscle and blood samples were collected from 10 animals each harvested at 2, 12, 24 and 48 h post-challenge. Immediately following harvest, samples were collected from the longissimus lumborum and again after 14 d of aging. Protein expression of HSPβ1 was analyzed in skeletal muscle samples taken prior to the ACTH challenge, at harvest, and after 14 d of aging. Expression of HSPβ1 was different (P < 0.05) at harvest between animals that were harvested at different points following induction of stress where steers that were harvested at 12 h had decreased expression when compared to those harvested at 48 h. In addition, time of harvest had an effect (P < 0.01) on cortisol concentrations, hemoglobin, hematocrit, white blood cells, neutrophils, monocytes, and eosinophils. Number of platelets, lymphocytes, and basophils did not differ (P > 0.05) between animals harvested at different time points. These data demonstrate that HSPβ1 protein expression in the longissimus lumborumafter harvest may be related to pre-mortem stress.