Effects Of Glutathione On Grouwth Performance And Antioxidant Function Of Yellow Catfish,Pelteobagrus Fulvidraco

This thesis intended to investigate the effects of glutathione on growth performance,immune and antioxidation,anti-apoptosis,anti-ammonia stress ability and related genes mRNA expression of juvenile yellow catfish(Pelteobagrus fulvidraco).The study comprises of five parts.1.Effects of dietary glutathione on growth performance,body composition and serum biochemical indices of juvenile yellow catfish(Pelteobagrus fulvidraco)A total of 800 yellow catfish with a mean body weight of(1.32±0.01)g were randomly divided into 5 groups with 4 replicates per group and 40 fishes per replicate.Fish were fed a basal diet and 4 test diets supplemented with 100,300,500,700mg/kg reduced glutathione,respectively.After 56 d feeding trial,ammonium chloride was used to conduct an ammonia nitrogen stress test in each group.The results showed that with the increasing of dietary glutathione levels,the weight gain rate,specific growth rate and protein efficiency rate increased at first but then decreased,achieving the maximum value in 300 mg/kg group,and 100~500 mg/kg groups were significantly higher than the control group(P<0.05);the feed conversation ratio,condition factor and hepatosomatic index had no significant difference(P>0.05).Compared with the control group,whole-body crude protein content in 300~700mg/kg groups and whole-body crude lipid in 100~700 mg/kg groups were significantly increased(P<0.05).Dietary glutathione had no significant effects on serum total protein,serum cholesterol and triglyceride,glucose,urea nitrogen contents and aspartate aminotransferase,alanine aminotransferase activities(P>0.05).In conclusion,dietary glutathione could increase growth performance and whole-body crude protein and crude lipid contents.A quadratic regression analysis on specific growth rate against dietary glutathione levels indicated that the optimal supplemental level of glutathione in the diet of juvenile yellow catfish was 357.69mg/kg.2.Effects of dietary glutathione on immunity and antioxidant capacity of juvenile yellow catfish(Pelteobagrus fulvidraco)After the feeding trial,samples of liver and serum of the fish were taken,and immunity,oxidant indices were analyzed.The results indicated that,except for 100mg/kg group,glutathione supplementation significantly increased glutathione content in liver and serum of yellow catfish(P<0.05).When dietary glutathione level was300 mg/kg or higher,glutathione content in liver and serum was in a stable state.With the increasing of glutathione levels in the diets,the immunity and antioxidant indices increased firstly and then decreased.The lysozyme and alkaline phosphatase activities in 300 mg/kg and 500 mg/kg groups,immunoglobulin M and complement 4 contents in 300 mg/kg group,acid phosphatase activity in 500 group increased significantly,compared with the control group(P<0.05).There was no significant differences(P>0.05)in complement 3 and nitric oxide contents among all groups.Compared with the control and 700 mg/kg groups,the liver superoxide dismutase,catalase and glutathione peroxidase activities,total antioxidant capacity and the serum superoxide dismutase,glutathione peroxidase activities in 300 mg/kg group were significantly higher(P<0.05);and the serum malondialdehyde content in 300 mg/kg group was significantly lower(P<0.05).In conclusion,dietary glutathione could increase immunity and antioxidant capacity of juvenile yellow catfish,and the suitable level was from 300~500 mg/kg.3.Effects of dietary glutathione on hemocyte apoptosis of juvenile yellow catfish(Pelteobagrus fulvidraco)When the feeding trial was finished,blood cells were taken and analyzed to detect apoptosis related indicators.The results showed that with the increasing of glutathione levels,blood active oxygen concentration and the apoptosis rate of yellow catfish was decreased at first but then increased,and in100~500 mg/kg groups were significantly lower than in control group and 700 mg/kg groups(P<0.05),and was the lowest in 300 mg/kg group.The blood calcium concentration in 100 and 300mg/kg groups was at a stable state,but increased from 500 mg/kg group,and in 500 and 700 mg/kg groups significantly higher than that in 100 and 300 mg/kg groups(P<0.05).In summary,dietary glutathione could reduce blood active oxygen concentration of yellow catfish,and make the blood calcium concentration maintain at a certain level,inhibit the apoptosis of blood cells,but high levels of glutathione would make the intracellular calcium concentration significantly increase,triggering apoptosis.4.Effects of dietary glutathione on anti-ammonia-nitrogen stress ability of juvenile yellow catfish(Pelteobagrus fulvidraco)After the feeding trial,20 fish from each replicate were randomly selected and stressed with ammonium chloride.After stress for 72 h and 96 h,cumulative mortality be counted,respectively,and after stress for 96 h,the serum and liver was collected to detect the related stress and antioxidant indexes.The results showed that after ammonia-nitrogen stress,the death time of yellow catfish fed diets containing glutathione was delayed than that of the control group,and during 96 h,the cumulative mortality rate of juvenile yellow catfish fed diets containing varied levels of glutathione was decreased when compared with the control group,and it was significantly decreased in 100 and 300 mg/kg groups(P<0.05).After stress for 96 h,with the increasing of glutathione content,the stress indicies were decreased first and then increased,and the serum cortisol concentration in each adding group was lower than in control group,reached significant level in 100 and 300 mg/kg groups(P<0.05),but there was no significant difference on blood ammonia nitrogen and urea contents in five groups(P>0.05).Compared with the control group,the liver and serum superoxide dismutase,catalase,glutathione peroxidase activities in 300mg/kg group were significantly higher(P<0.05);and the serum malondialdehyde content in 300 mg/kg group was significantly lower(P<0.05).In conclusion,dietary glutathione could reduce cumulative mortality rate,serum cortisol concentration and increase antioxidant enzymes activities of juvenile yellow catfish under ammonia-nitrogen stress.5.Effects of dietary glutathione on related growth,antioxidation and apoptosis genes mRNA expression of juvenile yellow catfish(Pelteobagrus fulvidraco)After the feeding trial,the liver was collected for quantitative fluorescence.The results showed that with the increasing of glutathione levels,the mRNA expression of igf1,bcl2,hsp70,tor genes of yellow catfish was increased firstly and then decreased, the mRNA expression of gst and bax genes was contrary.Compared with the control group,the mRNA expression of igf1 gene in 300 mg/kg group and 500 mg/kg groups,bcl2 gene in 100~500 mg/k groups and hsp70 gene in groups fed diets containing glutathione was significantly increased(P<0.05),the mRNA expression of bax gene in 300 mg/kg group was significantly decreased(P<0.05).However,the mRNA expression of gst and tor genes had no significant difference among the five groups(P>0.05).Thus,dietary glutathione could induce the mRNA expression of liver igf1,bcl2,hsp70,tor genes of juvenile yellow catfish,restrict the mRNA expression of gst and bax genes.