PSII-9 Free amino acids in pre- and post-rigor muscles from beef cattle under induced oxidative stress by hydrogen peroxide

Abstract

Abstract This study examined the effects of oxidative stress induced by hydrogen peroxide on free amino acids in pre-and post-rigor muscles from beef heifers (n = 18). Cattle were supplemented with ground corn and soybean hulls to 310 to 456 kg of BW while grazing cool and warm-season pastures and were evaluated for preliminary oxidative markers; afterward, they were shipped and finished at a commercial feedlot in Iowa. Animals were blocked into three groups based on prior analysis of oxidative stress markers and two treatments of either 20 mg hydrogen peroxide/kg BW (OX, n = 9) or 10 mL of saline (CON, n = 9) were equally and randomly assigned to animals within each block. On the day before slaughter, the OX and CON treatments were administered intravenously through the jugular vein. Pre-rigor muscles were collected at the neck (splenius) during slaughter; whereas post-rigor muscles were collected at the anterior of the beef loins (longissimus lumborum) at 72 h postmortem. Free amino acids were extracted in phosphate buffer, derivatized by propyl chloroformate, and determined by gas chromatography - mass spectrometry. Data were analyzed as a randomized complete block design with treatment, muscle rigor, and their interaction as fixed effects. Twenty-seven amino acids were quantified and ornithine and glutamine were 0.03 and 2.99 mmole/kg greater in OX muscle than in CON muscle (P = 0.031 and 0.024, respectively). Ten amino acids, such as glutamine and glutamic acid, were greater in pre-rigor muscles (P ≤ 0.003); whereas eleven amino acids were greater in post-rigor muscles, such as ß-aminoisobutyric acid and histidine (P ≤ 0.039). No treatment × time interaction was found (P > 0.069). Both ornithine and glutamine have been reported to reduce oxidative stress. Postmortem metabolism also greatly influences free amino acid concentrations.