202 Plasma Isoprostanes, but Not Thiobarbituic Acid Reactive Substances, Are a Reliable Measure of Lipid Oxidation in Growing Pigs Fed Peroxidized Soybean Oil

Abstract Past experiments have reported conflicting effects of feeding peroxidized soybean oil (pSO) to growing pigs on plasma F2-isoprostanes (ISP) and thiobarbituic acid reactive substances (TBARS) concentrations. Two experiments were conducted to clarify these inconsistencies. In experiment 1 (Exp. 1), 13.5 to 24.0 kg pigs were fed diets for 22 d which contained 10% SO that was either unheated or peroxidized (heated at 135°C for 42 h). In experiment (Exp. 2), 21.3 to 37.5 kg pigs were fed diets for 27d which contained either 8% SO or pSO. Blood was collected from 1 pig per pen on d 21 and 26 from Exp. 1 and Exp. 2, respectively, with plasma subsequently analyzed for ISP, TBARS, reactive oxygen metabolites (ROM), and antioxidant capacity (AXC). Data were analyzed as a randomized block design with experiment as the blocking factor. There were 10 replications per dietary treatment within each experiment. Pigs fed pSO had reduced gain, feed intake, and feed efficiency compared to pigs fed SO (P ≤ 0.01). Pigs fed pSO had increased concentrations of ISP (P ≤ 0.01), but tended to have decreased concentrations of TBARS (P = 0.10) compared to pigs to pigs fed SO. Pigs fed pSO had increased concentrations of ROM (P ≤ 0.01) while plasma concentrations of AXC did not differ (P = 0.28) compared to pigs fed SO. As a result, the oxidative stress index (OSi), based on the ratio between ROM and AXC, increased (P = 0.04) in pigs fed pSO compared to pigs fed SO. In conclusion, feeding pSO reduces pig performance and increases oxidative stress as measured by plasma ISP, ROM, and OSi. In contrast plasma TBARS were unaffected and may suggest they are not to be relied upon as a sole measure of oxidative stress, specifically lipid damage, in growing pigs.