Bruising in Slaughter Cattle and Its Relationship with Creatine Kinase Levels and Beef Quality as Affected by Animal Related Factors

The objective of the study was to determine the effects of animal related factors on bruising in slaughter cattle, creatine kinase (CK) and beef quality. Three hundred and twenty one cattle from three breeds (108 Bonsmara, 130 Beefmaster and 83 Brahman) were used in this study. The animals were grouped as follows: Group 1 (16 months old), Group 2 (18 months old) and Group 3 (24 months old). At exsanguinations, blood samples for CK determination were collected using disposable vacutainer tubes. Muscularis longissimus thoracis et lumborum (LTL) was collected 24 h after slaughter to determine the colour ($L^*$, $a^*$, and $b^*$) and ultimate pH ($pH_u$) of beef. Breed, sex and age had significant effects (p<0.05) on bruising score, CK levels and beef quality. Bonsmara breed had the highest (80%) bruising score percentage, CK ($705.3{\pm}80.57U/L$) and $pH_u$ ($6.3{\pm}0.05$) values while the Bonsmara had the highest $L^*$ ($24.8{\pm}0.78$) $a^*$ ($17.5{\pm}0.53$) and $b^*$ ($12.8{\pm}0.53$) values. Higher CK levels were also observed in winter compared to summer, spring and autumn respectively. Therefore, animal factors (sex, breed and animal age at slaughter) contribute to the development of bruises and have an effect on the levels of CK and meat quality. It was also concluded that there is no significant relationship between meat parameters (L,* $a^*$, and $b^*$) and CK levels.