Beef cattle exclusively raised under grazing conditions form the basis for the meat production around the world. Normally, the meat of these animals has some undesirable characteristics, such as lower terderness, higher pH and darker color when compared to animals fed in feedlot with grain-rich diets. The higher pH and a consequent darker coloring of the meat have been related to several factors, including inadequate pre-slaughter management practices that lead to the depletion of muscle glycogen reserves, consequently reducing the pH, leading to a darker colored meat. Although pasture-finished animals produce dark meat, this fact does not always recapitulate the biochemistry underlying DFD and thus may result from muscle changes in response to different production paradigms. Previous studies have shown that pasture-finished cattle produced darker meat, even when muscle glycogen levels were normal and also with similar final pH values. Although most of the evidence supports differences in the color of meat from pasture and feedlot animals, the mechanisms related to these differences are still unclear. In this sense, this work will be carried out to evaluate the impact of intensive and extensive feeding systems on muscle energy metabolism, postmortem metabolism and meat color development. Longissimus muscle samples of 40 cattle terminated with high or low growth diets and high or low concentrate, in a 2 x 2 factorial scheme will be used. Animals will be slaughtered at a relatively constant age and a final weight of 570 kg. After the slaughter will be evaluated pH, color, tenderness, mitochondrial function, in vitro glycolysis, metabolites (glycogen, glucose, G6P, lactated, NAD + and NADH), besides oxidative enzymes (succinate, dehydrogenase, citrate synthase, OXPHOS) enzymes of the glucose metabolism (glycogen phosphorylase, glycogen synthase, hexokinase and lactate dehydrogenase) and also the muscular morphometric profile.
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