Impacts Of Oxidative Stress On Piglets And The Anti-Stress Effects And Mechanism Of Selenium

One laboratory analysis experiment and four animal feeding trails were conducted to investigate the impacts of oxidative stress on piglets and the anti-stress effects and mechanism of selenium.Experiment 1. Methodology of oxidized oil production and peroxidation evaluationFresh fish oil or corn oil was prepared by mixing with Fe²⁺, Cu²⁺,H₂O₂ and H₂O and heating at temperatures of 37℃at constant fresh air supply. The degree of the peroxidation of the oils was determined by peroxidation value(POV), acid value (AV), thiobarbituric acid-reactive substances (TBARS) ,iodine value (â…£) and saponification value (SV). The regression equations of the peroxidized index with the peroxidation time (h) are as follows.For com oil: Y_POV= 0.0005X² + 0.1434X + 4.9404 (R² = 0.9924),Y^AV = 0.6X² - 0.0005X + 0.1596 (R²= 0.9837),Y_SV = 0.0005X² - 0.01X + 191.15 (R²= 0.9855),Y_TBARS = 0.06 X² + 0.0068X + 0.2539 (R² = 0.9924),Y_IV = -0.05X² - 0.0042X + 129.82 (R²= 0.9263);For fish oil: Y_POV = -0.692X² + 73.605X - 329.88 (R²=0.79),Y_AV = 0.3323X - 1.5745 (R² = 0.9472),Y_SV = 1.4071X- 184.27 (R²=0.917),Y_TBARS = -0.5643X² + 57.282X - 135.83 (R²=0.857) ,Y_IV = -0.0003X² - 0.4289X + 137.19 (R²=0.9776).The results suggested POV and TBARS of fish oil and corn oil were both increased quadratically as oxidative time extended, and fish oil was oxidized at more extent than corn oil at the same oxidative condition.Experiment 2. Impacts of oxidized fish oil on oxidative stress for pigletsBased on Exp.1,the purpose of this study is to investigate the effect of oxidized fish oil on growth performance and nutrient digestibility of piglets. Twenty-four piglets were allotted randomly to four groups according to a one factorial design. Each group had six replicates of one pig each. Pigs in four groups were fed a diet containing 3% of fresh oil(FFO) and oxidized fish oil with various POV (OFO1, OFO2 and OFO3), respectively. The feeding trail lasted for 4 weeks. Results showed that the oxidized fish oil depressed growth performance and nutrient digestibilities. Compared with FFO group, ADG was decreased by 8.16% (p＜0.05 ), F/G was increased by 9.22% (p＜0.05), apparent digestibilities of N, DM and lipid were decreased by 21.91% (p＜0.01 ), 13.05 % (p＜0.05 ) and 35.18 % (p＜0.05) for OFO3 group.The results suggested that the oxidized fish oil could depress performance and lower the nutrient digestibilities of the piglets. Among all groups, the group fed the diet containing 3% oxidized fish oil with POV 1065.74 meqO₂/kg had the most considerable impacts on piglets.Experiment 3. Impacts of diquat on oxidative stress for pigletsBased on Exp.1 and Exp.2,this study is to investigate the effect of diquat and oxidized fish oil on physiological functions of weanling pigs. Twenty four weanling pigs were allotted to three groups with 8 animals each according to a single factorial experimental design. Piglets received diets containing 5% fresh fish oil (group 1 and group 3) or oxidized fish oil(group 2), pigs in group 3 received an intraperitoneal injection of diquat at 12mg/kg of bodyweight at the beginning of the trial. The feeding trial lasted for 26d.Results showed that the growth performance,nutrient digestibilities, activities of antioxidant enzymes in the body tissues of group 2 and group 3 were decreased, and the contents of MDA in the body tissues of those groups were increased compared with group 1. The oxidized fish oil and diquat treatment depressed RBC, MCV, HGB, PLT, PCT and increased WBC of pigs. Compared with group 1, the villi height was decreased and the crypt depth of the jejunum was increased for group 2 and group 3.The jejunum and liver suffered certain pathological changes of group 1 and group 2. The results suggested that oxidized fish oil and diquat could both decrease the antioxidative enzymes and induce oxidative damage, break the balance of oxido-reduction steady status, and induce oxidative stress of piglets. Compared with the effects of oxidized fish oil,those of diquat were more strong.Experiment 4. Impacts of oxidative stress on cellular structure, immunological function of piglets and anti-stress effect of seleniumEffect of oxidative stress on cellular structure, immunological function of piglets and the effectiveness of selenium for anti-oxidative stress were investigated in this Exp.. Eighty-four piglets without vaccination for swine fever were allotted randomly to 7 groups according to a 2×3+1 factorial design. Each group had six replicates with two piglets each. Pig received injection of either diquat or sodium chloride at the beganning of the trial. Selenium was supplemented at 0, 0.2, 0.4 or 0.6 mg/kg in the diets.At the end of the third week of the trail, all the pigs were injected with swine fever vaccine. The results showed that oxidative stress decreased the growth performance and immune function but increased MDA levels, and resulted in injury of DNA of liver and spleen. Selenium supplementation could alleviate the impacts of oxidative stress. The concentration of IgG, IgA, IgM and the antibody for swine fever were significantly increased as selenium level in the diet increased. Compared with other groups, the effect of anti-stress of 0.6mgSe/kg group was the best. The results suggested that oxidative stress could induce damage the cell structure and both cellular and humoral immunity. Selenium supplementation could alleviate the damages.Experiment 5. The possible mechanism of selenium for anti-oxidative stressThe purpose of this experiment was to study the possible anti-stress mechanism of selenium through the detection of thyroid hormones, cytokine in serums and nuclear factor-κB in the liver and spleen. Experimental design was the same as Exp.4. The results showed that oxidative stress increased the levels of T3/T4, IL-1β, IL-6 and TSH in serum, and the activities of NF-Kb p65 in the liver and spleen. Selenium supplementation could reverse the changes induced by oxidative stress. The results suggested that selenium could influence the hypothalamus-appendix eerebri-thyroid or immunological cell, regulate the seeretion of T₃, T₄ and TSH and generation of IL-1βand IL-6, suppress the activation of NF-κb to play it's anti-stress functions.