| Oligomeric proanthocyanidins(OPC)has a wide range of sources and strong antioxidant activity.The adequate OPC supplementation level in diets could improve the growth and health status of some fish species under different stresses.At present,no researches have been conducted to study the application of dietary OPC supplementation in eels.Therefore,the different levels of OPC were supplemented in diet of eels under different stress conditions,and the effects of dietary OPC supplementation on growth performance,serum biochemical parameters and intestinal health status were studied to evaluate the supplementation effects of OPC in juvenile eels.Trial I Effects of dietary OPC supplementation on the growth,serum biochemical parameters and intestinal health status juvenile eels fed diet with high histamine levelFour hundred and eighty juvenile American eels with an average body weight of 10.84±0.16 g were randomly divided into 4 groups with 4 replicates per group and 30 fish per replicate.The four treatment groups were control group(the basal diet),H group(the basal diet+300 mg/kg histamine),H+OPC group I(the basal diet+300mg/kg histamine+300mg/kg OPC),and H+OPC group II(the basal diet+300mg/kg histamine+600 mg/kg OPC group),respectively.The trial period was 77 days.The results were showed as follows.Compared with H group,the weight gain rate and specific growth rate of H+OPC groups were significantly increased(P<0.05).The parameters about body composition in whole fish were not significantly affected(P>0.05).The activities of lipase in intestine was significantly improved(P<0.05),and the activities of amylase and protease were similar(P>0.05).The activities of acid phosphatase,alkaline phosphatase and levels of VC,VE,Immunoglobulin M and complement 3 were significantly increased(P<0.05).The activity of diamine oxidase and level of D-lactate were significantly decreased(P<0.05).The other serum parameters were not significantly affected(P>0.05).Compared with H group,the levels of total antioxidant capacity in intestine of H+OPC groups were significantly increased(P<0.05),the level of malondialdehyde was significantly decreased(P<0.05),the activities of superoxide dismutase and catalase were similar(P>0.05).The density of intestinal fold was obviously increased(P<0.05),and fold height was not affected significantly(P>0.05).The Chao1 index in H+OPC groups were significantly increased(P<0.05),while the Shannon index in H+OPC group I was significantly increased(P<0.05),and that of H+OPC group II were not affected significantly(P>0.05).The relative abundances of intestinal flora dietary OPC supplementation were significantly affected(P<0.05).The relative abundances of Firmicutes and Actinobacteria were increased,and the relative abundances of Proteobacteria and Fusobacteria were decreased.The relative abundances of bacteria including Aeromonas,Pseudomonas and Acinetobacter were decreased,and the relative abundance of bacteria including Lactobacillus was significantly increased.The results were not significantly different from H+OPC group II(P<0.05).There were not significant differences of on growth performance,serum biochemical parameters,antioxidant capacity in intestine,the diversity and relative abundance of intestinal flora between H+OPC group I and H+OPC group II(P>0.05),and the those parameters were similar in H+OPC group and control group(P>0.05).Trial II Effect of dietary OPC supplementation on the growth,serum biochemical parameters and intestinal health status juvenile eels cultured in intensive ponds with water recirculation systemThe juvenile European eels cultured in nine intensive ponds with water recirculation system were randomly divided into three treatment groups with three replicates in each group with an average body weight of 10.84±0.16 g/fish.The average fish weight in each pond was672.75±5.54 kg.The dietary OPC levels of the three treatment groups were 0(control group),300 and 600 mg/kg,respectively.The trial period was 105 days.The results were showed as follows.Compared with control group,the weight gain rate and specific growth rate of OPC groups were significantly increased(P<0.05),and the feed coefficient ratio in 600 mg/kg OPC group were decreased(P<0.05).The activities of protease and lipase in intestinal tract were significantly increased(P<0.05),the activities of amylase were not affected significantly(P>0.05).The serum activities of transaminase and diamine oxidase and levels of total cholesterol were significantly decreased(P<0.05).It was found that significant differences of levels of VC,VE(except 600mg/kg OPC group)and IgM and activities of acid phosphatase,alkaline phosphatase between control group and OPC groups(P<0.05).The other serum parameters were not affected significantly(P>0.05).Compared with control group,the levels of malondialdehyde of OPC groups were significantly decreased(P<0.05).The levels of total antioxidant capacity and glutathione(except300mg/kg OPC group)were significantly increased(P<0.05),the activities of superoxide dismutase and catalase were similar(P>0.05).Indexes of Chao1 and Shannon of intestinal flora were affected significantly by dietary OPC supplementation(P<0.05).The values of those indexes in 300 mg/kg OPC group was highest and higher than those of other two groups(P<0.05).The relative abundances of Spirochaetaeand and Bacteroidetes in intestinal flora were increased,the relative abundance of Firmicutes was decreased.The relative abundances of Aeromonas and Polynucleobacter were decreased,and the relative abundance of Brevinema was increased.The growth performance,serum biochemical parameters(except the 600 mg/kg OPC group with higher level of IgM than that of 300 mg/kg group)and antioxidant capacity in intestine were not different significantly between the two OPC(P>0.05).Indexes of Chao1 and Shannon of intestinal flora of 600 mg/kg OPC group were lower than those of 300 mg/kg OPC group(P<0.05).The relative abundances of Firmicutes and Proteobacteria in intestinal flora were decreased,and the relative abundance of Spirochaetae was increased(P<0.05).The relative abundances of bacteria including Brevinema were increased,and the relative abundance of bacteria including Mycobacterium was decreased.In conclusion,under the condition of stress of dietary histamine level or in intensive ponds with water recirculation system with poor water quality,dietary 300mg/kg OPC supplementation could effectively improve growth performance and the activities of some digestive enzymes,have beneficial adjustment in serum biochemical parameters,improve the liver health status and antioxidant ability of intestine,and regulate the intestinal flora beneficially.The health status in fish intestine was improved obviously.The growth-promoting effects of 300 mg/kg and 600mg/kg OPC supplementation on juvenile eel were similar. |
PDF Full Text Request