Influence of feeding thermally peroxidized soybean oil on growth performance, digestibility, gut integrity, and oxidative stress in nursery pigs

Authors: Kerr, Brian; LINDBLOM, STEPHANIE - Iowa State University; OVERHOLT, MARTIN - University Of Illinois

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2020
Publication Date: 2/1/2020
Citation: Kerr, B.J., Lindblom, S.C., Overholt, M.F. 2020. Influence of feeding thermally peroxidized soybean oil on growth performance, digestibility, gut integrity, and oxidative stress in nursery pigs. Journal of Animal Science. 98(2). https://doi.org/10.1093/jas/skaa016.
DOI: https://doi.org/10.1093/jas/skaa016

Interpretive Summary: Soybean oil and soybean oil products, 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. The digestibility and caloric value of refined, deodorized, bleached soybean oil is well documented in swine, but there is limited data on the impact of thermally processed (i.e., peroxidized) soybean oil on pig performance, energy and lipid digestibility, gastrointestinal integrity, and oxidative stress in nursery pigs. The current study was conducted to evaluate the effect of thermally processing soybean oil at 45C, 90C, and 180C on pig performance, energy and lipid digestibility, gastrointestinal integrity, and oxidative stress in nursery pigs compared to pigs fed unprocessed soybean oil. Data from this experiment indicate that the presence of lipid peroxidation products contained in the soybean oil thermally processed at 90C reduced pig gain and feed intake, and increased oxidative stress as measured by serum isoprostane concentration and urinary isoprostane excretion. In contrast, thermal processing of soybean oil at any time and temperature combination had no effect on energy, lipid, or nitrogen digestibility, or on intestinal permeability. This information is important for nutritionists at universities, feed companies, and pig production facilities for the determination of the impact on pig performance and caloric value of thermally processed soybean oil in feed formulations, and provides a basis from which to assess their economic value.

Technical Abstract: The objective of the current experiments was to evaluate the effect of feeding soybean oil (SO) with different levels of peroxidation on lipid, N, and GE digestibility, gut integrity, oxidative stress, and growth performance in nursery pigs. Treatments consisted diets containing 10% fresh SO (22.5C) or thermally processed SO (45C for 288 h, 90C for 72 h, or 180C for 6 h), each with an air infusion of 15 L/min, with post-processing peroxide values of 7.6, 11.5, 19.1, and 13.4 mEq/kg and anisidine values of 1.92, 6.29, 149, and 159; for the 22.5, 45, 90 and 180oC processed SO, respectively. In Exp. 1, 64 barrows (7.1 ± 0.9 kg initial BW) were randomly allotted into 2 rooms of 32 pens, and individually fed their experimental diets for 21 d; with a fresh fecal sample collected on d 20 for determination of GE and lipid digestibility. In Exp. 2, 56 barrows (BW 9.16 ± 1.56 kg) were placed into individual metabolism crates for assessment of GE, lipid, and N digestibility, and N retention. Urinary lactulose to mannitol ratio was assessed to evaluate in vivo small intestinal integrity and urine and plasma were collected to analyze for markers of oxidative stress. Pigs were subsequently euthanized to obtain liver weights and analyze the liver for markers of oxidative stress. In Exp. 1 pigs fed the SO thermally processed at 90C had reduced ADG (P = 0.01) and ADFI (P = 0.04) compared to pigs fed the other SO treatment groups, with no differences noted among pigs fed the 22.5C, 45C, and 180C SO treatments. No effects of feeding thermally processing SO on dietary GE or lipid digestibility (P > 0.10) were noted in either experiment. In Exp 2, there was no dietary effect of feeding peroxidized SO on the DE:ME ratio, N digestibility, or N retained as a percent of N digested, on the urinary ratio of lactulose to mannitol, on serum, urinary, or liver TBARS, on plasma protein carbonyls, or on urinary or liver 8-OH-2dG (P > 0.10). In Exp. 2, pigs fed the SO thermally processed at 90°C had the greatest ISP concentrations in the serum (P = 0.01) and urine (P = 0.05) compared to pigs fed the unprocessed SO. These results indicate that the change in FA composition and/or the presence of lipid peroxidation products in peroxidized SO may reduce ADG and ADFI in nursery pigs, but appears to have no impact on GE, lipid, or N digestibility, or gut permeability. The data suggest that the presence of lipid peroxidation products may affect certain markers of oxidative stress.