| This study aimed to explore the oxidant stress effect of oxidized diets formulated with aging corn and oxidized oil on growing-finishing pigs,and investigate the protective effects of 2-hydroxy-4-methylselenobutanoic acid(Se O)supplementation.40 Duroc ×Landrace × Yorkshire(DLY)boars with similar body weight(25±3)kg were selected and randomly divided into 5 groups,8 repeats in each group,1 pig per repeat.The positive control group was fed on basal diet(BD,using normal maize and normal oil)without selenium supplementation;The oxidized treatment groups were fed on diets that using Aging corn(harvested at 2014)and oxidized oil to replace the normal maize and oil used in the BD diets and supplied with 0 mg Se/kg Selenium(Negative control),0.3 mg Se/kg Se O,0.6 mg Se/kg Se O,0.9 mg Se/kg Se O.The trial lasted for 16 weeks and growth performance,meat quality,antioxidant capacity,inflammatory genes and selenoprotein encoding genes in tissues were investigated.The main results are as following:1)The oxidized diets had a tendency(P > 0.05)to reduce on ADFI,ADG,and F/G at different stages of pigs.The addition of different levels of dietary Se O had limited effect(P > 0.05)to improve the growth performance of pigs fed on oxidized diets,although 0.9mg/kg Se O groups exhibited a relative higher(P > 0.05)ADFI and ADG at each stage.2)Only one pig in oxidized diet group died during the trial and autopsy of the died pig showed typical “yellow fat disease” symptom.No morbidity and mortality were found in control group and selenium supplementation groups.3)The oxidized diet significantly reduced the carcass quality of pigs(P < 0.05),which decreased(P < 0.05)the carcass length,carcass weight,slaughter rate,backfat thickness,abdominal fat percentage and eye muscle area by 5.5%,10.2%,2.7%,25.1%,23.9%,and 12.1%,respectively.Dietary levels of Se O exhibited protective effects and improved(P < 0.05)carcass quality of pigs fed on oxidized diet.Supply Se O at 0.9 mg/kg Se O increased(P < 0.05)the carcass weight,and supply Se O at 0.3 mg/kg and 0.6 mg/kg increased(P < 0.05)the eye muscle area;the addition of Se O allevialted(P > 0.05)the negative effects of oxidized diet on carcass length,abdominal fat percentage and slaughter rate.4)The oxidized diet increased(P < 0.05)the spleen index and thymus index and Se O supplementation decreased or had a tendency to decrease spleen index,renal index and thymus index of pigs faced with dietary oxidant stress.Oxidized diet increased(P > 0.05)the liver index,and dietary Se O addition further increase liver index of the stressed pigs.5)The oxidized diet sharply decreased selenium level in serum and muscle tissue.Dietary Se O supplementation effectively increased(P < 0.05)serum selenium level and selenium deposition in muscle of pigs.Selenium deposition in muscle exhibited a linear dose depend manner.6)The oxidized diet had a trend to increase(P > 0.05)drip loss,increased(P < 0.05)the b* at 48 h,reduced(P < 0.05)the marbling score,while had limited impact on(P >0.05)on p H,L*,a* value in longissimus muscle of pigs.Se O exhibited protective effects and 0.6 mg/kg and 0.9 mg/kg Se O supplementation reduced the drip loss at 48 h in pigs fed on oxidized diet,also dietary Se O addition improved(P < 0.05)other measurments related to meat quality.7)The oxidized diet reduced(P < 0.05)the activity of GSH-Px in serum,the activity of T-AOC in liver,spleen and longissimus dorsi,and increased(P < 0.05)the content of MDA in the spleen.Different levels of Se O supplementation recovered or even further improved antioxidant attributes in above tissues,thus alleviated the negative effect of oxidized diet on growing-finishing pigs.Both levels of Se O supplemetation increased(P <0.05)the activity of GSH-Px in serum,liver and spleen,increased(P < 0.05)the activity of T-AOC in liver and spleen,and increased the activity of T-SOD in liver and longissimus muscle.8)The oxidized diet increased(P < 0.05)or had a tendency to increase pro-inflammatory cytokines levels in serum and organic Se supplied in form of Se O effectively alleviated immunological response induced by oxidized diet in pigs.9)The oxidized diet had a tendency to up-regulate(P > 0.05)m RNA levels of ICAM-1,IL-1β,IL-6,IL-8,IL-10,MCP-1 and TNF-α in liver,exhibited limited effect(P >0.05)on expression of 10 inflammation-related genes in spleen.The addition of levels of Se O exhibited impact on expression of inflammation-related genes in tissues of pigs under stress.10)The oxidized diet had a tendency to decrease(P > 0.05)m RNA levels of selenoprotein encoding genes in liver and spleen,while increased(P > 0.05)most genes in muscle.Dietary Se O supplementation exhibited impact on expression of selenoprotein encoding genes in tissues of stressed pigs.The addition of Se O moderately increased(P <0.05)expression of 21 selenoprotein encoding genes in liver of pigs.In spleen the addition of Se O had limited effect on the expression of most selenoprotein encoding genes.In muscle tissues,supplied selenium in form of Se O exhibited impact on expression of most selenoprotein encoding genes.11)The oxidized diet significantly up-regulated the expression of Myh4(P < 0.05)and had a tendency to down-regulated the expression of Myh1,Myh2 and Myh7 in longissimus dorsi muscle(P > 0.05).Dietary levels of Se O supplementation down-regulated the expression of Myh4(P < 0.05)and up-regulated the expression of Myh2 and Myh7 in muscle tissues of pigs faced with dietary induced oxidant stress,thus contribute to the improvement of meat quality.Conclusion: Oxidized diets formulated with aging corn and oxidized oil caused the oxidant stress effects on growing-finishing pigs.Although oxidant stress had no significant effect on the growth performance of pigs,it decreased the carcass trait and meat quality,decreased selenium disposition and antioxidant capacity in tissues and increased pro-inflammatory cytokines levles in serum;Dietary Se O supplementation effectively alleviated the oxidant stress effect and improved the meat quality.Those protective effects of selenium supplied in form of Se O were associated with regulation expression of selenoprotein encoding genes and inflammatory genes in corresponding tissues. |
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