| Oxidative stress is a phenomenon in which excessive reactive oxygen radicals in organisms lead to weakened scavenging ability of oxygen free radicals in tissues or cells,resulting in self-oxidative damage and thereby breaking the balance between oxidation and antioxidant status of the body.Oxidative stress may adversely affect the growth performance and immune function of aquatic animals.In this study,the effects of oxidized fish oil and vitamin E on the growth,antioxidant capacity and digestive tract flora of Strongylocentrotus intermedius were studied by the activity of enzyme determination,fluorescence quantitative analysis,liquid chromatography and Illumina HiSeq high-throughput sequencing.The main research results are as follows:(1)Effects of oxidized fish oil on growth,antioxidant capacity and flora in digestive tract of juvenile Strongylocentrotus intermedius: the juvenile sea urchins(initial weight 1.50 ± 0.2g)was used as experimental object to study the effect of oxidized fish oil on growth,antioxidant capacity and flora in digestive tract of sea urchins by feeding growth experiment.Six kinds of dietaries with equal nitrogen and lipids were compound by adding equal amounts of different peroxide values(POV)of fish oil(0,50,100,150,200 and 300 meq/kg),and they were named as OF0,OF50,OF100,OF150,OF200 and OF300,and fresh kelp was used as the control group(HD).The experimental period was 60 days.The results showed that the WGR of sea urchins decreased with the increase of fish oil peroxidation value in the feed,and it had the lowest value in OF300 group,which was significantly lower than that of HD and F0 group(P<0.05).With the increase of fish oil peroxidation value in the feed,the antioxidant index,the activities of immune enzymes and digestive enzymes(pepsin,AMS and CL)showed a trend of decreasing first and then increasing.The activities of antioxidant enzyme,pepsin and AMS had the lowest values in the higher peroxide experimental groups(OF150 and OF200 groups),the activity of CL had the lowest values in the OF50 group,and the activities of immune enzymes had the lowest values in the OF100 and OF150 groups.The content of MDA was increasing.The activity of LPS in the digestive tract of sea urchins gradually increased,and the higher peroxide experimental group(OF150,OF200 and OF300 groups)was significantly higher than other feed groups(P<0.05).With the increase of fish oil peroxidation value in the feed,the expression of antioxidant enzyme genes(GST and GPX),related inflammatory genes(COX-2,TNF-? and AIF-1)and related immune genes(TLR,LYZ,HSP70,NLR6 and 185/333-1)were showing an increasing trend.The expression of COX-2,TNF-?,GPX,HSP70,NLR6 and 185/333-1 in OF0 group were significantly lower than those in OF300 group(P<0.05).With the increase of fish oil peroxidation value in the feed,the abundance of Bacteroidetes in the digestive tract of sea urchins gradually increased,while the abundance of Firmicutes gradually decreased.And the abundance of Proteobacteria,uncultured bacterium f Rhodobacteraceae and the Lutibacter in the digestive tract of the sea urchins increased first and then decreased.The abundance of Vibrio in the digestive tract of the sea urchins decreased first and then increased.The experimental results showed that oxidized fish oil could slow the growth of juvenile sea urchins,the WGR of sea urchin fed with kelp was significantly higher than those fed with feeds.When the peroxide value of oxidized fish oil in the feed was lower than 100 meq/kg,oxidized fish oil has less adverse effects for juvenile sea urchins in the antioxidant capacity,immunity and the activities of digestive enzymes.In addition,oxidized fish oil will also change the composition of flora in the digestive tract,reduce the abundance of Firmicutes,increase the abundance of Bacteroidetes.(2)The effect of vitamin E on the growth,antioxidant capacity and flora in digestive tract of juvenile Strongylocentrotus intermedius: the juvenile sea urchins(initial weight 3.75 ± 0.37g)was used as the experimental object to study the effect of vitamin E on the growth,antioxidant capacity and flora in digestive tract of sea urchins by feeding growth experiment.The experimental period was 90 days.Six kinds of dietaries with equal nitrogen and lipids were compound by gradient adding of vitamin E(50,150,250,350,450 and 550 mg/kg),and they were named as E50,E150,E250,E350,E450 and E550,and fresh kelp was used as the control group(HD).The results showed that the WGR of the sea urchins in the feed group increased first and then decreased with the increase of vitamin E content in the feed,but there was no significant difference(P>0.05).The WGR of sea urchins in the HD group was significantly higher than that in the E50 group(P< 0.05).With the increase of vitamin E content in the feed,the activities of antioxidant enzymes and immune enzymes in coelomic fluid of the sea urchins decreased first and then increased,which reached the lowest value in the E250 group.When adding high levels of vitamin E(E350,E450,and E550 group)to the feed,the content of MDA in coelomic fluid of the sea urchins decreased.The highest value in the E350 group.The activity of pepsin in the digestive tract of E550 group was significantly lower than that in other groups(P<0.05).The activities of LPS,AMS and CL in the digestive tract of the sea urchins in the feed group increased first and then decreased.The activities of LPS and AMS had the highest value in the E350,the activity of CL had the highest value in E150 group.With the increase of vitamin E content in the feed,the expression of related inflammatory factors(COX-2,TNF-? and AIF-1)in the digestive tract of the sea urchins decreased first and then increased,and they all reached the lowest value in the E250 group.When adding high levels of vitamin E(E350,E450,and E550 group)to the feed the expression levels of antioxidant enzyme genes(GST and GPX)and related immune genes(TLR,LYZ,HSP70,NLR6 and 185/333-1)in the digestive tract of the sea urchins decreased,and all had the highest value in the E350 group.With the increase of vitamin E content in the feed,the abundance of Proteobacteria,Actinobacteria,Ruegeria and Maliponia in the digestive tract of the sea urchins in the feed group increased.With the increase of vitamin E content in the feed,the abundance of the Firmicutes,Bacteroidetes,Escherichia-Shigella,Bacteroides and Clostridium sensu stricto gradually decreased.However,the ratio of Firmicutes to Bacteroidetes was gradually increasing.The abundance of Phaeobacter increased first and then decreased.The abundance of Rhodococcus was firstly decreased and then increased.Therefore,when the lipid level in the feed was 12.00%,the addition of vitamin E in the feed promotes the growth of juvenile sea urchins,the optimum dosage was 450 mg/kg.The optimum dosage was 250 mg/kg according to antioxidant capacity and immunity.The optimum dosage was 150-350 mg/kg according to the activities of digestive enzyme.The optimum dosage was 550 mg/kg according to the content of VE in gonad of urchins.Vitamin E affected the structure and abundance of flora in digestive tract,and increased the ratio of the Firmicutes to the Bacteroidetes.(3)Effects of dietary supplementation of different levels of vitamin E with moderately oxidized fish oil on the growth,antioxidant capacity and flora in digestive tract of juvenile Strongylocentrotus intermedius: the juvenile sea urchins(initial weight 2.30 ±0.16 g)was used as experimental object to study the effect of dietary supplementation of different levels of vitamin E on growth,antioxidant capacity and flora in digestive tract of sea urchins by feeding growth experiment.Six kinds of dietaries with nitrogen and lipids were compound by gradient adding of vitamin E(50,150,250,350,450 and 550 mg/kg)and equal moderately oxidized fish oil,and they were named as E50,E150,E250,E350,E450 and E550,and fresh kelp was used as the control group(HD).The experimental period was 60 days.The results showed that the WGR of the sea urchins increased first and then decreased with the increase of vitamin E content in the feed,and the maximum value in the E250 group,but there was no significant difference between the other groups(P>0.05).The WGR of sea urchins in the HD group was significantly higher than that of the OFE50 group(P<0.05).With the increase of vitamin E content in feed,the activities of antioxidant enzymes and immune enzymes in coelomic fluid increased first and then decreased,and both of them showed the maximum in the lower level of vitamin E(OFE150,OFE250 and OFE350 groups).And the content of MDA in coelomic fluid of the sea urchin was generally increased.The content of MDA in coelomic fluid of OFE350 group,OFE450 group and OFE550 group was similar(P>0.05),which was significantly higher than other feed groups(P<0.05).The activities of digestive enzymes in the digestive tract of the sea urchin were increased first and then decreased,which had the maximum in the higher level of vitamin E(OFE350 and OFE450 groups).With the increase of vitamin E content in the feed,the expression levels of inflammatory factors(COX-2,TNF-? and AIF-1)in the digestive tract of the sea urchin showed decrease first and then increase,which had the maximum in OFE350 groups.And the expression of antioxidant enzyme genes(GPX)and immune genes(TLR,LYZ,HSP70,and NLR6)in the digestive tract of the sea urchin increased first and then decreased,which had the maximum in the groups with lower level of vitamin E(OFE150,OFE250 and OFE350 groups).The expression of GST and 185/333-1 decreased first and then increased,which had the maximum in theOFE450 group and OFE250 group,respectively.With the increase of vitamin E content in the feed,the abundances of Proteobacteria,Phaeobacter and Maliponia in the digestive tract of the feed group decreased first and then increased.And the abundances of Firmicutes,Actinobacteria,Bacteroidetes and Rhodococcus showed a trend of increasing first and then decreasing.However,the ratio of Firmicutes to Bacteroidetes was gradually decreasing.The abundance of Ruegeria was generally increased.Therefore,when the lipid oxidation value of the feed was 100 meq/kg and the fat content is 12.00%,adding 250 mg/kg vitamin E to the fed,the addition of vitamin E in the feed promotes the growth of juvenile sea urchins,the optimum dosage was 250 mg/kg.The optimum dosage was 250-350 mg/kg according to antioxidant capacity and immunity.The optimum dosage was 350-450 mg/kg according to the activities of digestive enzyme.The optimum dosage was 550 mg/kg according to the content of VE in gonad of urchins.The supplementation of vitamin E with moderately oxidized in the feed could decrease the radio of Firmicutes to Bacteroidetes. |
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