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Browsing by Author "Gruber, L. Sandra, author"

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    Effects of pre-slaughter cattle management on postmortem tenderization of beef
    (Colorado State University. Libraries, 2009) Gruber, L. Sandra, author; Tatum, J. Daryl, advisor
    Two independent studies were used to investigate the effects of pre-slaughter cattle management on postmortem tenderization of beef. In experiment I, relationships between behavioral and physiological symptoms of pre-slaughter stress and beef LM tenderness were examined using calf-fed steers (n = 79) and heifers (n = 77). Pen, chute, and post-transportation behavior scores were assigned to each animal. Physiological indicators of stress included cortisol, epinephrine, creatine kinase, lactate, glucose, heart rate, respiration rate, and rectal temperature. Positive correlations (P < 0.05) between behavior scores and physiological parameters indicated that cattle that exhibited behavioral symptoms of stress also responded physiologically. Mean Warner-Bratzler shear force (WBSF) was positively correlated (P < 0.05) with all 3 measures of stressful behavior (r ≥ 0.23). Plasma lactate concentration at slaughter was associated (P < 0.05) with mean WBSF and response to postmortem aging. In Experiment II, effects of genotype and implant program on LM and gluteus muscle (GM) postmortem tenderization were investigated using crossbred steer (n = 185) and heifer (n = 158) calves. The 3-marker GeneSTAR Tenderness panel was used to determine each animal's genotype. Calves were assigned to 1 of 2 implant programs, conventional or delayed. Steaks from conventionally implanted cattle had WBSF values that were approximately 0.2 kg higher (P < 0.05) than steaks from animals that received a single delayed implant, but only during the early postmortem period (3 to 7 d). For both muscles, a linear effect of genotype on WBSF was detected (P < 0.05). Steaks from cattle with most desirable genotype had WBSF values 0.33 kg lower than steaks from cattle with the least desirable genotype. Pre-slaughter factors (sex, implant program, and genotype) controlled in Experiment II each accounted for less than 10% of the explained variation in tenderness of the experimental population. Results of Experiment I identified behavioral and physiological symptoms of acute pre-slaughter stress that were associated with pH-independent differences in tenderness. Findings from Experiment II suggest that pre-slaughter cattle management can impact beef tenderness, but the factors evaluated only accounted for a small proportion of variation in beef tenderness for the experimental population.