Influence of feeding thermally peroxidized soybean oil on oxidative status in growing pigs

Authors: LINDBLOM, STEPHANIE - Iowa State University; GABLER, NICHOLAS - Iowa State University; DILGER, RYAN - University Of Illinois; Bond, Zahra; Loving, Crystal; Kerr, Brian

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2018
Publication Date: 3/6/2018
Publication URL: https://handle.nal.usda.gov/10113/6472195
Citation: Lindblom, S., Gabler, N., Dilger, R., Olson, Z.F., Loving, C.L., Kerr, B.J. 2018. Influence of feeding thermally peroxidized soybean oil on oxidative status in growing pigs. Journal of Animal Science. 96:545-557. https://doi.org/10.1093/jas/sky005.

Interpretive Summary: Soybean oil and products derived from soybean oil, such as recycled restaurant grease, can be an important source of energy in swine feeding programs because they provide a concentrated source of energy compared to other commonly used feedstuffs. While the digestibility and caloric value of refined, deodorized, bleached soybean oil is well documented in swine, there is limited data on the impact of thermally processed (i.e., peroxidized) soybean oil on pig performance, energy and lipid digestibility, and gastrointestinal integrity in growing pigs. The current study was conducted to evaluate the effect of thermally processing soybean oil at 45 C, 90 C, and 180 C on pig performance, energy and lipid digestibility, and gastrointestinal integrity in growing pigs compared to pigs fed unprocessed soybean oil. Data from this experiment indicates that the presence of lipid peroxidation products contained in the thermally processed soybean oil induces oxidative stress as indicated by increasing damage of serum proteins, increasing the excretion of urinary isoprostanes and thiobarbituric acid reactive substances, increasing DNA damage in the liver, and diminishing serum glutathione peroxidase. This information is important for nutritionists at universities, feed companies, and pig production facilities for the determination of the impact of thermally stressed soybean oil on the oxidative status of growing pigs which may affect its value in feed formulations.

Technical Abstract: The objectives of this study were to determine whether feeding thermally processed peroxidized soybean oil (SO) induces markers of oxidative stress and alters antioxidant status in pig tissue, blood, and urine. Fifty-six barrows (25.3 ± 3.3 kg initial BW) were randomly assigned to dietary treatments containing 10% fresh SO (22.5 C) or thermally processed SO (45 C for 288 h, 90 C for 72 h, or 180 C for 6 h), each with constant air infusion rate of 15 L/min. Multiple indices of lipid peroxidation were measured in the SO including peroxide value (2.0, 96, 145, and 4.0 mEq/kg for 22.5, 45, 90 and 180oC processed SO, respectively) and p-anisidine value (1.2, 8.4, 261, and 174 for 22.5, 45, 90 and 180 C processed SO, respectively); along with a multitude of aldehydes. Pigs were individually housed and fed ad libitum for 49 d which included a 5 d period in metabolism crates for the collection of urine and serum for measures of oxidative stress. On d 49, pigs were euthanized to determine liver weight and analyze liver-based oxidative stress markers. Oxidative stress markers included serum, urinary, and liver thiobarbituric acid reactive substances (TBARS), and urinary F2-isoprostanes (ISP) as markers of lipid damage; serum and liver protein carbonyls (PC) as a marker of protein damage; and urinary and liver 8-hydroxy-2'-deoxyguanosine (8-OH-2dG) as a marker of DNA damage. Superoxide dismutase (SOD), and catalase activity (CAT) were measured in liver, glutathione peroxidase activity (GPx) was measured in serum and liver, and ferric reducing antioxidant power (FRAP) was measured in serum and urine as determinants of antioxidant status. Pigs fed 90 C SO had greater urinary ISP (P = 0.02), while pigs fed the 45 C SO had elevated urinary TBARS (P = 0.02) in comparison to other treatment groups. Pigs fed 45 C and 90 C SO had increased serum PC concentrations (P = 0.01) and pigs fed 90 C SO had greater (P = 0.01) liver concentration of 8-OH-2dG compared to pigs fed the other SO treatments. Furthermore, pigs fed 90 C SO had reduced serum GPx activity in comparison to pigs fed fresh SO (P = 0.01). In addition, pigs fed 180 C SO had increased liver CAT activity (P = 0.01). Liver GPx and SOD or serum and urinary FRAP were not affected by dietary treatment. These results indicate that dietary peroxidized soybean oil induced oxidative stress by increasing serum PC while diminishing serum GPx, increasing urinary ISP and TBARS, and increasing 8-OH-2dG and CAT in liver.