The relationship between postmortem urinary catecholamines, meat ultimate pH, and shear force in bulls and cows

We investigated the relationship between stress responsiveness and meat quality in cattle. The cattle were 16-19-month-old Mixed (n=37, 303 kg) or Non-mixed (n=23, 279 kg) Friesian bulls and Friesian cull cows (1.5-7 years) that were classified Unfinished (n=133, 195 kg) or Finished for 3 months (n=34, 252 kg). A portion of m. longissimus lumborum (LL) muscle was obtained from consecutive animals for a single days slaughter of 227 cattle processed through a hot boning plant. Catecholamines were obtained from bladder urine. Ultimate pH, lactate, glycogen, glycolytic potential and representative sarcomere lengths were determined from 20-h muscle samples. Shear force measurements were from meat aged at 15 °C for 20 and 90 h. Urinary noradrenaline was similar between Mixed (14.86 ng/μmol creatinine) and Non-mixed bulls (14.07 ng/μmol creatinine) and Finished cows (15.24 ng/μmol creatinine) and elevated in the Unfinished cows (22.28 ng/μmol creatinine). Urinary adrenaline was higher in Mixed bulls (9.5 ng/μmol creatinine) than Non-mixed bulls (5.7 ng/μmol creatinine) and higher in both Unfinished cows (16.67 ng/μmol creatinine) and Finished cows (14.19 ng/μmol creatinine). For bulls that are growing well on-farm, with a only short period of fasting prior to slaughter, pH(u) is a good predictor of meat tenderness. In this situation, stressors that lower muscle glycogen pre-slaughter can have a significant effect on meat shear force, and individual animals with elevated urinary adrenaline were the most susceptible. However, in the case of cows, adrenaline responses are not necessarily associated with glycogen depletion and pH(u) is less affected than for bulls. Furthermore, the ability of meat to tenderise fully, related to reduced proteolytic turnover, is reduced in nutritionally compromised animals such as the Unfinished cows.