PSII-8 - Free amino acids in blood plasma of beef cattle under induced oxidative stress by hydrogen peroxide

This study examined the effects of oxidative stress induced by hydrogen peroxide on free amino acids in blood plasma 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 principal component 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 group. On the day before slaughter, the OX and CON treatments were administered intravenously through the jugular vein. Blood samples were collected immediately before and 90 min after treatment, centrifuged into plasma, aliquoted, snap-frozen in liquid nitrogen, and stored at -80°C. Free amino acids in plasma were derivatized by propyl chloroformate, extracted in isooctane, and determined by gas chromatography – mass spectrometry. The data were analyzed as a randomized complete block design with repeated measures with treatment, time, and their interaction as fixed effects. Twenty-seven amino acids were quantified and sarcosine concentration was 1.5 mM greater in OX plasma than in that of CON (P = 0.064). Leucine, threonine, proline, asparagine, methionine, and α-aminobutyric acid were greater pre-treatment (P ≤ 0.006); whereas cystine was greater at 90 min post-treatment (P = 0.019). Although the effects of hydrogen peroxide injection on free amino acids in blood plasma were minimal, an increase in sarcosine concentration has been reported as a marker of induced oxidative stress.