| Astragalus polysaccharides(APS)is the main natural active ingredient extracted from the dried roots of the Chinese herb Astragalus,which has various functions such as antioxidant,anti-inflammatory,immunomodulatory and regulation of intestinal flora,and is widely used as a feed additive in livestock and poultry production,but has not been seen in swamp eel(Monopterus albus).However,it has not been used in swamp eel.In this experiment,we investigated the effects of APS on the growth performance,digestibility,antioxidant capacity,serum biochemical indexes,glucose metabolism and intestinal flora of swamp eel to provide a theoretical basis for the application of APS in the production of eels and to provide theoretical guidance for the optimization of artificial feeds for swamp eel.Experiment 1: Effect of APS addition to feed on growth performance,digestibility,antioxidant capacity,serum biochemical indexes,glucose metabolism and intestinal health of swamp eel.The swamp eel(initial body weight: 5.21±0.17 g)were randomly divided into five groups and fed five equal-nitrogen and equal-lipid diets with feed APS levels of 0 g/kg(A1),0.5 g/kg(A2),1 g/kg(A3),2 g/kg(A4)and 4 g/kg(A5)for a period of 60 days.The results of the experiment showed that:(1)with the increase of the feed APS level,the survival rate,liver-to-body ratio,dirty-to-body ratio and fatness of each group were not significantly different(P>0.05),while the final body weight,weight gain rate and specific growth rate showed a trend of increasing and then decreasing,and all of them were significantly higher in the A4 group than the control group(P<0.05),and the feed factor showed a trend of decreasing and then increasing,and was significantly lower in the A4 group than the control group(P<0.05).The feed coefficient was the lowest when the weight gain rate reached the maximum at 2 g/kg of APS addition.By linear regression analysis,the best values of weight gain rate and feed coefficient were found at 2.001 g/kg and 2.193 g/kg of APS addition,respectively.The addition of APS to the feed had no significant effect(P>0.05)on whole fish body composition moisture,ash and muscle body composition moisture,crude protein,crude fat and ash,whole fish crude protein showed a tendency to rise and then fall(P<0.05)and was highest in group A4,whole fish crude fat showed a tendency to rise(P<0.05)and was highest in group A5.(2)APS had a significant effect(P<0.05)on the liver and intestinal amylase and APS had a significant effect(P<0.05)on eel liver and intestinal amylase and lipase,with a trend of rising then falling,reaching the highest in group A4,and no significant effect(P>0.05)on both liver and intestinal trypsin.(3)There was no significant effect of APS level in feed on serum glutathione transaminase,glutathione transaminase,triglycerides,urea nitrogen,glucose globulin and albumin ratio of eels(P>0.05),serum LDL and total cholesterol showed a decreasing trend with the increase of APS level,and all reached the lowest in group A4(P<0.05)Serum HDL,total protein and albumin showed a trend of increasing,then decreasing,then increasing,and all reached the highest in group A4(P<0.05).(P<0.05).(4)APS had no significant effect on serum acid phosphatase,alkaline phosphatase and liver acid phosphatase in eels(P>0.05),with the increase of APS level,serum superoxide dismutase,catalase and liver alkaline phosphatase,superoxide dismutase and catalase showed a trend of first increase and then decrease(P<0.05),all in the A4 group.A4 group,and serum and liver malondialdehyde showed a trend of first falling and then rising,both lowest in A4 group(P<0.05).(5)APS level had no significant effect on myoglycogen and serum pyruvate kinase,phosphoenolpyruvate carboxykinase and hepatic phosphoenolpyruvate carboxykinase activities in swamp eel(P>0.05),and hepatic glycogen and hepatic pyruvate kinase activities in groups A4 and A5 were significantly higher than those in group A1(P<0.05).6)APS is beneficial to increase the diversity and homogeneity of intestinal flora and increase the relative abundance of intestinal flora.In conclusion,APS can improve the growth performance of eels,increase the antioxidant capacity of eels by increasing the activity of antioxidant enzymes,promote glucose metabolism,and optimize the structure of intestinal flora at the same time.It is suggested that the appropriate amount of APS in swamp eel feed should be 2 g/kg – 2.2 g/kg.Experiment 2: In this experiment,the effect of APS on the re-feeding of swamp eel after starvation was analyzed on the basis of experiment 1.The eels with initial weight of(9.87 ± 0.11 g)were subjected to starvation re-feeding,numbered S1-S4.S1 group was the control group,fed feed without APS for 30 d and starved for 0 d.S2,S3 and S4 groups were the experimental groups,S2 group was starved for 15 d and then fed feed containing APS for 15 d,S3 group was starved for 15 d and then fed feed without APS for 15 d,S4 group was starved for 30 d and fed for 0 d.added APS,and group S4 was starved for 30 d and fed for 0 d.After 30 d of culture trials,the digestive enzyme activity,antioxidant capacity and sugar metabolism indexes of eels were measured respectively.The test results showed that:(1)the final body weight,survival rate,weight gain rate,relative liver weight and liver-to-body ratio of S1-S4 groups all showed a decreasing trend(P<0.05),and the survival rate and weight gain rate of S2 group were significantly higher than those of S3 group(P<0.05).(2)The intestinal and liver trypsin,lipase and amylase activities of S1-S4 groups showed a decreasing trend,and the difference between the groups was significant(P<0.05),and the intestinal trypsin,lipase and amylase activities of S2 group were significantly higher than those of S3 group(P<0.05).group had significantly higher intestinal trypsin,lipase,amylase and hepatic trypsin than S3 group(P<0.05).(3)Serum acid phosphatase and catalase were significantly higher in S1 group than in S2-S4 group(P<0.05),and there was no significant difference in serum acid phosphatase and catalase in S2 and S3 groups(P>0.05);liver acid phosphatase,alkaline phosphatase,catalase and malondialdehyde all showed a decreasing trend(P<0.05),and catalase was significantly higher in S2 group than in S3 group(P<0.05);there was no significant effect on serum and liver SOD(P>0.05).(4)Liver glycogen in S1-S4 groups showed a decreasing trend(P<0.05),liver glycogen in S2 group was significantly higher than that in S3 group,and the difference of muscle glycogen in each group was not significant(P>0.05);liver and serum pyruvate kinase and phosphoenolpyruvate carboxykinase in S2 and S3 groups were not significantly affected(P>0.05).The above results indicate that.Starvation re-feeding of APS is beneficial to the recovery of the nutrient level of the swamp eel organism,improving its growth performance,liver and intestinal digestive enzyme activity,antioxidant capacity and promoting glucose metabolism. |
PDF Full Text Request