Effect of growth intensity of bulls on the microstructure of musculus longissimus lumborum and meat quality

The aim of this study was to evaluate the effect of growth intensity of 43 bulls with different growth intensity (. Commercial crosses of Polish Lowland black-and-white cows with Charolais and Limousin bulls were used in this study; within the particular genetic groups the hybrids had similar slaughter weight (447.6 and 517.2 kg) and age (526 and 606 days), respectively. The share of fibres with active tetrazole dehydragenase in the more intensively growing animals was smaller. For fibres with myofibrillar ATPase activity, the intensively growing animals produced higher standard deviation values than the other groups. Further analysis of the muscular tissue in this group revealed that out of the 24 muscles, 9 had giant fibres. In comparison with the less intensively growing animals, the muscles of the bulls that gained more than 900 g/day in weight were found to contain significantly less glycogen (P ≤ 0.01) and, consequently, the meat was less acidic. The difference of the pH ranged from 0.19 in the case of pH24 (P ≤ 0.01) to 0.06 for pH48 (P ≤ 0.01). It should be noted that the intensively growing animals were found to have a relatively high pH variability (SD = 0.69 and 0.49, respectively). The pH24 and pH48 values, as well as pH variability show that the meat of this group was dark, firm and dry