Relationships of behavioral and physiological symptoms of preslaughter stress to beef longissimus muscle tenderness1

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.

Cortisol Hormone Concentration and Meat Quality of Beef Cattle Stunned by Captive Bolt Stun Gun before Slaughtering

“…Beef that has pH u > 6.0 after slaughtering indicates a change in the quality of meat. The meat has a dark red color (dark firm and dry/DFD) (Gruber et al, 2010), a high level of tenderness variation, and low palatability (Mach et al, 2008).…”

Concentração de lactato, peso corporal e qualidade da carne em bovinos Nelore terminados em confinamento

“…GrUBer et al (2010) encontraram valores médios de 11,97 mMol/L para a concentração de lactato no período pós-abate em bovinos Angus, valores próximos aos encontrados no presente estudo, e concluíram que a maioria dos bovinos (70%) demonstram sintomas de estresse e aumento das concentrações sanguíneas de lactato quando submetidos ao manejo físico ou após serem transportados.…”

“…Segundo GrUBer et al (2010), bovinos com altas concentrações de lactato sanguíneo produzem carnes menos macias, com maior força de cisalhamento.…”

Livestock-handling assessments to improve the welfare of cattle, pigs and sheep

“…Physiological measures can easily show differences between low-stress and high-stress handling (Edwards et al 2010;Brandt and Aaslying 2015). At the slaughter plant, when pigs and cattle were moved with electric prods or jammed in the race that leads to the stunner, lactate and glucose concentrations are higher (Edwards et al 2010;Gruber et al 2010). Edwards et al (2010) measured blood lactate in pigs and Gruber et al (2010) measured plasma lactate and plasma glucose in cattle.…”

“…At the slaughter plant, when pigs and cattle were moved with electric prods or jammed in the race that leads to the stunner, lactate and glucose concentrations are higher (Edwards et al 2010;Gruber et al 2010). Edwards et al (2010) measured blood lactate in pigs and Gruber et al (2010) measured plasma lactate and plasma glucose in cattle. Benjamin et al (2001) found that both glucose and blood lactate were doubled or tripled immediately after aggressive handling with multiple shocks from an electric prod, compared with calm handling with no prods.…”