Tenderness of beef round muscles containing injection site lesions or bruises

The effect of injection site lesions on shear force was studied in three experiments using beef calves injected at 2 to 6 mo with common vaccines and antimicrobials used in Canada. Lesions produced by clostridia) bacterins (Blacklegol(R) 8, Covexin(R)-8, Ultrabac(R) 8), antimicrobials (Nuflor(R), Trivetrin(TM)), or a four-way respiratory vaccine (Bovishield(TM) 4) increased (P less than or equal to 0.05) shear force values at the site of the lesion and at 2.5 cm from the lesion. The proportion of unacceptably tough meat cores (shear force > 4.6 kg) varied among injectables independent of lesion size. The proportion of unacceptably tough samples was significantly increased up to 7.5 and 12.5 cm from the lesion center for Trivetrin(TM) and Nuflor(R), respectively, but only at 0 and 2.5 cm from the lesion center for the bacterins and Bovishield(TM) 4. Mean lesion volume varied from 8.6 +/- 0.8 cm(3) for Bovishield(TM) 4 to 90.2 +/- 6.4 cm(3) for one of the clostridial bacterins. The present results suggest that smaller lesions, which may not be identified during meat processing, may have a greater impact on meat tenderness and variability than larger lesions that are removed during processing. Antemortem bruises in two muscles of the round did not appear to affect shear force.