Cattle with more reactive temperaments have lower resting muscle glycogen

The objective of this experiment was to evaluate the effect of differences mammal temperament on muscle glycogen and lactate concentration. The temperament of 81 Angus steers was assessed seven times between weaning and yearling age using flight speed (m/s) and crush score (1 to 5) measurements . Muscle biopsy samples were collected four times from the semimembranosus (SM) and semitendinosus (ST) during the pasture finishing phase (around 18 to 24 months) and immediately after slaughter from each steer. Each biopsy was analysed for glycogen and lactate, and glycogen depletion due to pre-slaughter stress was calculated as the difference between on-farm glycogen and muscle glycogen at slaughter. An increase m flight speed from 0 .75 to 2.25 m/s was associated with a reduction in muscle glycogen concentration by 8 .9% (P<0 .05) and an increase in muscle lactate concentration by 17.3% (P<0.01) m both the SM and ST. An increase in crush score from 1.25 to 3 reduced muscle glycogen by I 0.4% (P<0.05) in the SM and ST and increased lactate in the ST by 42% (P<0 .05). Thus, animals with calm temperaments had higher resting glycogen concentration and mobilised less during stress compared to more excitable animals. However, the effect of temperament on glycogenolysis pre-slaughter or glycogen concentration at slaughter was not evident, most likely due to these animals becoming habituated to human contact. In conclusion it is likely that improved temperament will increase muscle glycogen concentration prior to slaughter and reduce the incidence of dark, firm, dry beef.