Relationships of behavioral and physiological symptoms of preslaughter stress to beef longissimus muscle tenderness.
ABSTRACT Relationships between behavioral and physiological symptoms of preslaughter stress and LM Warner-Bratzler shear force (WBSF) were investigated using Bos taurus steers (n = 79) and heifers (n = 77). Measurements of heart rate, respiration rate, rectal temperature, and concentrations of serum cortisol and plasma epinephrine were used as indicators of stress associated with physical handling and chute restraint, whereas concentrations of cortisol, glucose, lactate, and creatine kinase in blood samples obtained at exsanguination were measured to reflect physiological reactions of animals to transportation stress. Increased plasma epinephrine concentration, indicative of acute handling stress, was associated with elevated heart rate (r = 0.42, P < 0.001) and rectal temperature (r = 0.34, P < 0.001) during restraint, increased plasma lactate (r = 0.22, P = 0.006) and serum creatine kinase (r = 0.28, P < 0.001) concentrations at slaughter, and greater LM WBSF (r = 0.22, P = 0.006). Plasma lactate concentration at slaughter, which reflected an adrenergic stress response to transportation, was associated with lesser final LM pH (r = -0.30, P < 0.001) and greater LM WBSF (r = 0.26, P = 0.002). Categorical analyses of chute and posttransportation behavior scores (calm vs. restless vs. nervous) showed that cattle exhibiting adverse behavioral reactions to handling and chute restraint had increased (P < 0.05) values for plasma epinephrine concentration, heart rate, and rectal temperature during chute restraint, elevated (P < 0.05) plasma lactate concentration at slaughter, and increased (P < 0.05) LM WBSF. In addition, cattle showing behavioral symptoms of stress after transportation had greater (P < 0.05) plasma glucose and lactate concentrations at slaughter and produced LM steaks that were 0.34 kg tougher (P < 0.05) when compared with calm cattle. No carcasses were identified as dark cutters, and LM pH did not differ (P > 0.05) among behavior categories. Grouping cattle according to differences in plasma lactate concentration categorized them according to mean differences in LM WBSF. Moreover, steaks from cattle with the greatest plasma lactate concentrations at slaughter (91st to 100th percentile) had a delayed response to aging that persisted until 14 d postmortem. Stress-induced differences in LM tenderness observed in this study were independent of differences in muscle pH.
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ABSTRACT: Stress is the inevitable consequence of the process of transferring animals from farm to slaughter. The effects of chronic stress on muscle glycogen depletion and the consequent dark cutting condition have been well documented. However, there has been little examination of the consequences of acute stress immediately pre-slaughter on ruminant meat quality. New evidence is emerging to show that non pH-mediated effects on meat quality can occur through pre-slaughter stress in cattle and sheep. This paper reviews the general aspects of pre-slaughter stress in the pre-slaughter context. It then examines the impacts of pre-slaughter stressors on ruminant carcass and meat quality and considers remedial strategies for remediating and preventing pre-slaughter stress. Further quantification of the biological costs of pre-slaughter stress and the consequences to meat quality is required.Meat Science 09/2008; 80(1):12-9. · 2.75 Impact Factor
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ABSTRACT: Stress is a broad term that implies a threat to which the body needs to adjust. Stress can be classified as physical, psychological, or interoceptive in nature but usually contains components of all three classifications. The adjustment to stress induces a broad range of physiological and behavioral changes that allow for a rapid recovery or adaptation to the change. In the past, housing systems and handling pro- cedures for farm animals were mainly assessed by de- scriptive behavioral studies using indicators presumed to be related to stress (i.e., stereotypic behaviors). Phys- iological indicators included endocrine changes of the pituitary-adrenal-axis by measuring ACTH, cortico- steroids, and catecholamines. The neuroendocrine and immune systems have been studied in relation to stress effects at the cellular or neural level during the last decade. All these studies were often conducted in an isolated manner without considering that the neuroen- docrine and immune systems are communicating with