Sick Neonatal Foals Do Not Demonstrate Evidence of Oxidative Stress

Critical illness in humans is associated with alterations in oxidative stress and the concentration of antioxidant molecules; however, this association has not been examined in equine neonates. The purpose was to determine the concentration of various antioxidant molecules, as well as a marker of oxidative stress, in the serum and plasma of normal and sick neonatal foals and their dams. Results demonstrated that the concentration of selenium was less (61.71 vs. 77.93 ng/mL; P = .002) in sick versus healthy neonates, whereas the concentration of vitamin E was slightly higher in sick compared with healthy foals (4.36 vs. 3.17 mg/mL); however, this did not achieve statistical significance (P = .31). The vitamin E concentration was greater (5.37 vs. 3.43 mg/mL; P = .01) and serum selenium was less in sick mares (129.50 vs. 184.78 ng/mL; P = .0001) compared with healthy mares. In addition, the serum concentration of selenium is lower in neonates than in their dams in the perinatal period (70.10 vs. 173.34 ng/mL; P = .0001). Glutathione peroxidase activity was less in sick foals (7.04 nmol/min/mL) compared with healthy foals (9.13 nmol/min/mL) (P = .19), and 3-nitrotyrosine (3-NT) concentration/mg protein was less in sick foals versus healthy foals (geometric mean, 1.24 vs. 2.07 nmol 3-NT/mg protein). This difference did not achieve statistical significance (P = .09); however, when a subset of critically ill foals was examined, the assayed concentration of 3-NT/mg protein was even less (0.99 nmol 3-NT/mg protein) and did statistically differ from healthy foals (P = .03).