| Selenium is an essential trace element added to animals’ diets as sodium selenite(SS),selenomethionine(Se-Met)and/or Se-enriched yeast(SY).The application of these additives in feed were restricted due to their side effects.This study was conducted to assess the efficacy and tolerance of a new organic selenium--hydroxy-analogue of selenomethionine(HMSeBA)for weaned piglets.On the one hand,to assess the effects of different levels on growth performance,serum/tissue selenium deposition,serum/liver antioxidant status of piglets;and to exploreing metabolic difference by comparing the key metabolic enzymes and selenoprotein gene expression in the same dose of different selenium sources.On the other hand,to assess the effects of high dose of HMSeBA for weaned piglets by researching the effects on hematological parameter and serum biochemical indexes,organ indexes and histopathology.All of these was to elucidate the efficacy and tolerance of HMSeBA on weanling piglets and provide scientific basis for its development and utilization.A total of 288 healthy crossed piglets[Duroc ×(Landrace × Yorkshire)],weaned at～21 d of age,were randomly assigned into 8 dietary treatment groups with 6 replicates/pens per treatment and 6 pigs per replicate on the basis of body weight and gender.The dietary treatments were negative control(NC)group(basal diet without extra Se),positive control(PC)group(basal diet + 0.3 mg/kg Se from Na2SeO3),and 5 HMSeBA groups(basal diet + 0.1,0.2,0.3,0.4,0.5,4 mg/kg Se from HMSeBA,respectively).The pigs were fed a basal diet for a 3-day of adaptation,and after that the pigs were fed corresponding diets as described above for 28 d.At the end of the feeding trial,six pigs from each treatment were selected,fasted for 12 h,and then harvested.(1)Effects of different levels of HMSeBA on growth performance,selenium deposition and antioxidant status in weaned piglets.The results indicated that:1)Dietary Se(Na2SeO3 and HMSeBA)did not affect the growth performance of weaned piglets(P>0.05);The ADG in 4 mg/kg HMSeBA group was significantly decreased compared with 0.3 mg/kg HMSeBA group(P<0.05),but it was not significantly different among other groups(P>0.05);The diarrhea rate in 0.2mg/kg>0.3mg/kg HMSeBA groups was significantly decreased(P<0.05)。2)The serum,liver,kidney and longissimus dorsi Se concentrations were respectively increased as the dietary Se(Na2SeO3 and HMSeBA)supplementation,and kidney>liver>muscle>serum.Compared with Na2SeO3,HMSeBA was more effectively increasing the serum and tissues Se deposition,and showed a linear(P<0.001)and quadratic curve(P<0.001)relationship;3)Serum T-AOC.T-SOD and GSH-Px activities was accordingly increased with the increase of HMSeBA level.Compared with NC and PC groups,the T-AOC was significantly increased in 0.4 mg/kg HMSeBA groups(P<0.05),0.4,0.5mg/kg HMSeBA groups significantly increased T-SOD activity compared with NC group(P<0.05),and 0.5 mg/kg and 4mg/kg HMSeBA group significantly increased GSH-Px activity of weaned piglets(P<0.05):Compared with 0.3mg/kg Na2SeO3 group,the content of MDA in the same amount HMSeBA group of was significantly decreased(P<0.05).It was no significant difference of T-AOC in 4mg/kg HMSeBA group compared with NC and PC groups(P>0.05),T-SOD activity was significantly decreased(P<0.05).GSH-Px activity was significantly increased(P<0.05),the content of MDA was significantly lower than that of PC group(P<0.05).but it was no significant difference compared with other groups(P>O.05).Liver T-AOC,T-SOD and GSH-Px activities was also accordingly increased with the increase of HMSeBA level.Compared with NC and PC groups,the T-AOC in 0.3 mg/kg HMSeBA group was significantly increased(P<0.05),0.4 mg/kg HMSeBA significantly increased the activity of T-SOD in comparison with NC group(P<0.05),but it was not different among Se treatment groups(P>0.05).Se supplement(Na2SeO3 and HMSeBA)significantly increased GSH-Px activity and decreased the MDA content in liver(P<0.05).4mg/kg HMSeBA decreased the activity of T-SOD(P<0.05),the GSH-Px activity was higher than NC group(P<0.05).(2)Effects of the same dose of different selenium source(0.3 mg/kg Na2SeO3 and 0.3 mg/kg HMSeBA)on the key enzymes of selenium metabolism and selenoprotein gene expression.The results indicated that:1)Compared with NC and 0.3mg/kg Na2SeO3 groups,dietary supplementation 0.3mg/kg HMSeBA significantly increased the expression of CBS,CGL,SCLY and GSR mRNA in weaning piglets(P<0.05),Compared with NC group,0.3 mg/kg Na2SeO3 significantly increased the expression of Trxl mRNA in liver(P<0.05),but it was not different from that of 0.3mg/kg HMSeBA(P>0.05).2)Compared with NC group,dietary supplementation of 0.3mg/kg HMSeBA significantly increased the expression of selenoprotein SPS2 and GSH-Pxl mRNA in weaning piglets(P<0.05),but there was no significant difference in the expression of SPS2 and GSH-Pxl mRNA compared with 0.3mg/kg Na2SeO3 group(P>0.05);Compared with NC and 0.3mg/kg Na2SeO3 groups,the expressions of TrxRl and SeIP mRNA in 0.3mg/kg HMSeBA group were significantly increased(P<0.05).The expression of SelP mRNA in 0.3mg/kg Na2SeO3 group was also significantly increased(P<0.05).(3)Effects of high dose of HMSeBA on blood indexes,organ indexes and histopathology in weaned piglets.The results indicated that:1)Compared with NC and 0.4 mg/kg HMSeBA groups,the HGB and HCT in 4mg/kg HMSeBA group was significantly decreased,but the WBC,RBC,PLT had no treatment effect(P>0.05);The ALB content in 4 mg/kg HMSeBA group was lower than NC and 0.4 mg/kg groups(P<0.05),the CR content in 4 mg/kg HMSeBA group was lower than CN group,but the ALT,AST,ALP,TCHO,Urea,UA,TPRO,GLU,TBILI content among these treatments have no significant difference(P>0.05).2)Compared with 0.4 mg/kg HMSeBA group,the lung index in 4 mg/kg HMSeBA group was significantly increased(P<0.05),but it had no difference with that of NC group(P>0.05);Compared with NC group,the kidney index in 4 mg/kg HMSeBA group was significantly increased(P<0.05),and it also had no significantly difference with 0.4mg/kg HMSeBA group(P>0.05);The heart index,liver index and spleen index have no significantly difference among these treatments(P>0.05).3)Dietary supplemental 0.4 and 4 mg/kg Se in the form of HMSeB A had no negative effect on heart,liver,spleen,lung and kidney tissues.In conclusions,our results have demonstrated that:(1)Under the conditions of this trial,dietary supplementation of different levels of HMSeBA did not affect growth performance,but the serum/tissues Se deposition and antioxdation of weaned piglets were improved by HMSeBA.Dietary supplementation of organic Se(HMSeBA)could promote the gene expressions of key enzymes of selenium metabolic pathways and selenium protein,and the effect was better than that of inorganic selenium(Na2SeO3).The best recommended dose of Se from HMSeBA for piglets diet was 0.2～0.4 mg/kg.(2)Dietary 4 mg/kg Se from HMSeBA had no obvious negative effect on growth performance,hematological parameter,serum biochemical indexes,organ indexes and histopathology in weaned piglets,4 mg/kg HMSeBA is within the safe dose range of weaned piglets. |
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