| This thesis was conducted to investigate the effects of dietary mulberry leaf flavonoids(MLF)on growth performance,body composition,serum and liver antioxidant indexes,resistance to nitrite exposure,muscle quality indexes and a ntioxidant enzyme m RNA expression of GIFT,Oreochromis niloticus.The contents and results are as follows: 1 Effects of dietary MLF on growth performance,body composition,serum and liver antioxidant indexes of GIFT,Oreochromis niloticus840 fish with an initial body weight of 1.51±0.02 g were randomly divided into 6 groups with 4 replicates of 35 fish,and fed with basal diet and 5 tested diets respectively for 56 d.The five test diets were prepared by adding MLF 50,100,300,500 and 1 000 mg/kg to the basal diet,respectively.The results showed that there was no significant difference in growth multiple(GM),feed conversion(FC)and protein efficiency rate(PER)among the groups(P>0.05).No significant differences were found among all groups in the crude protein,crude lip id,ash and moisture contents of whole body(P>0.05).Serum superoxide dismutase(SOD),glutathione peroxidase(GSH-Px)activities and total antioxidant(T-AOC)in MLF-supplemented groups were higher than in the control.Serum SOD activity in 100,300,500,and 1 000 mg/kg groups were significantly higher than that in the control(P<0.05).In comparison with the control,serum GSH-Px activity in 50,500,and 1 000 mg/kg groups was significantly increased(P<0.05).Serum malondialdehyde(MDA)content was decreased significantly in the MLF-supplemented groups(P<0.05).Liver SOD,catalase(C AT)activities and T-AOC in 100,300 and 500 mg/kg groups were significantly higher than those in the control(P<0.05).The highest value of SOD activity in liver was observed in 100 mg/kg group,and significantly higher than that in 1 000 mg/kg group(P<0.05).These results suggest that dietary MLF do not significantly affect the growth performance,but significantly improve serum and liver antioxidant indexes of GIFT,Oreochromis niloticus.By analysis of the regression equation,the optimal supplemental level of MLF in the diet of GIFT,Oreochromis niloticus was calculated to be 100 mg/kg on the basis of SOD and T-AOC,and using the activity of liver SOD and T-AOC as the evaluation index,it was found that the optimal supplemental level of MLF in the diet of GIFT,Oreochromis niloticus was 371.00~441.75 mg/kg.2 Effects of dietary MLF on resistance to nitrite exposure of GIFT,Oreochromis niloticusAfter 56 d feeding trail,the nitrite exposure experiment was conducted.After 48 h,72 h nitrite exposure,the cumulative mortality rate in 50,100 and 500 mg/kg groups was significantly decreased when compared to the control(P<0.05).The time of similar cumulative mortality in the supplementation group s was delayed by 24 h compared to the control.The serum SOD activity in 1 000 mg/kg group increased significantly in comparison with the control(P<0.05).The serum GSH-Pxactivity in 50 and 100 mg/kg groupswas increased significantly than 1 000 mg/kg groups(P<0.05);the GSH-Pxactivity in 300 and 500 mg/kg groupswas increased significantly than the control and the other supplementation groups(P<0.05).The serum C AT activity in 100,300 and 500 mg/kg groupswas increased significantly than the control and the other supplementation groups(P<0.05).Serum MDA contentin 500 and 1 000 mg/kg groups was significantly lower than the control(P<0.05).Compared to thecontrol,liver SOD and GSH-Pxactivity in 50 and 300 mg/kg groups was significantly increased(P<0.05).Liver CAT activity in 100 mg/kg group was significantly higher than 500 and 1 000 mg/kg groups(P<0.05),but not significantly different from the control(P>0.05).Liver T-AOC in 100 and 500 mg/kg groups was significantly higher than that in the control(P<0.05).The present study indicates that dietary MLF could decrease the cumulative mortality rates significantly and improve antioxidant activity of GIFT,Oreochromis niloticusunder nitrite exposure.3 Effects of dietary MLF on muscle quality of GIFT,Oreochromis niloticusAfter feeding trial,the muscle quality was analyzed.The results showed that no significant differences were found among all groups in the crude protein,crude lipid,ash,moisture contents and drip loss of muscle(P>0.05).Muscle collagen in 500 mg/kg group was significantly higher than that of control.The muscle SOD activity in 100 and 300 mg/kg groups was increased significantly in comparion with the control(P<0.05).Muscle T-AOC in 500 mg/kg group was significantly higher than that of control and 1 000 mg/kg,while MDA content in 50,100,300 and 1 000 mg/kg groups was significantly lower than that of control.Muscle phenylalanine content in 50 mg/kg group and alanine content in 100 mg/kg were significantly higher than those of the control.Muscle leucine,methionine and glutamic acid content of 50 mg/kg group were significantly increased compared to the control.The content of muscle histidine in 1 000 mg/kg group was significantly higher than that in control.The results showed that the dietary MLF could significantly improve the content of muscle collagen,antioxidant indexes and the amino acid composition.4 Effects of dietary MLF on the m RNA expression of antioxidant enzymes gene m RN A in liver and muscle of GIFT,Oreochromis niloticusAfter the above mentioned alternative experiment was finished,the liver and muscle sample was prepared.The m RN A expression of SOD,CAT and GSH-Px genes were determined using quantitative real-time polymerase chain reaction.The results showed thatthe highest m RN A expression level of SOD in liver was found in 100 mg/kg group,and significantly higher than that in the control(P<0.05).The highest m RNA expression level of CAT in liver was found in 100 mg/kg group,and significantly increased in comparison with the other treatments(P<0.05).In 50,100 and 300 mg/kg groups,the expression of CAT in muscle was significantly higher than in 1 000 mg/kg group(P<0.05).There was no significant difference in the expression of GSH-Px in liver among the groups(P>0.05).No significant differences were found among all groups in the expression of GSH-Px in muscle(P>0.05).In conclusion,dietary MLF could induce the m RN A expression of antioxidant related genes in liver and muscle of GIFT,Oreochromis niloticus. |
PDF Full Text Request