Effects Of Fermented Feed On Growth Performance,Digestive Enzyme Activity,Fillet Quality And Immunity Of Juvenile Carp(Cyprinus Carpio)

In recent years,the aquaculture industry has developed rapidly in China.Accordingly,the demand for feed was increasing,and the shortage of feed resources has became increasely serious.Meanwhile,the intensive aquaculture has led to the outbreaks of fish diseases.The use of antibiotics has caused significant concerns about the aquatic environment and food safety.Therefore,it was of great significance to find safe and scientific methods to enhance the immunity and disease resistance of fish.Fermented feed is a promising feed resource for aquatic animals.It could not only alleviate the shortage of feed resources,but also improve the immunity of animal,and then have the potential to replace antibiotics.However,the application of fermented feed in aquaculture has been influenced by a lot of factors.In order to scientifically evaluate the beneficial effects of fermented feed on aquatic animals,common carp(Cyprinus carpio),one of the most important economic fish in China,was adopted as the target animal in this study.And the benificial effects of fermented feed for juvenile carp were investigated taking into account the growth performance,whole-body composition,intestinal digestive enzyme activity,fillet quality,immunity and liver antioxidant capacity.The results obtained could provide technical basis for the application of fermented feed in aquaculture,and the development of new aquatic feed resources.The study included two parts:Experiment 1 Effects of fermented feed on the growth performance,fillet quality and digestive enzyme activity of juvenile carp(Cyprinus carpio)The purpose of this study was to explore the effects of fermented feed on the growth performance,body composition,intestinal digestive enzyme activity and fillet quality of juvenile carp.A total of 5 experimental feeds were prepared:the basal feed(G1),the basal feed supplemented with 2.5%(G2)or 5.0%(G3)of fermented feed,5%(G4)or 10%(G5)of fermented feed substituting the rapeseed meal in basal feed.Three hundred carp were randomly divided into five groups,there were four repetitions in each group,and each repetition had fifteen tails of carp,and each group was fed with one kinds of feed.Fish were fed three times daily for 10 weeks.After the feeding trial,the fish,intestine and muscle samples were collected with the parameters measured.The results showed that the feed conversion ratio of G1 was significantly higher than that of G3,G4 and G5(P<0.05),but showed little difference with that of G2(P>0.05).In addition,no significant difference was observed in specific growth rate,weight gain,final body weight,feed intake,protein efficiency ratio,nitrogen retention efficiency and energy retention efficiency among all the groups(P>0.05).No significant difference was observed in whole-body moisture,protein,lipid,ash and energy contents as well as the water-holding capacity,cooking loss,meat content,muscle texture and flesh color(namely the a*,b*and L*value)(P>0.05).The intestinal lipase and amylase activities of G4 were significantly higher than those of G1(P<0.05).In summary,fermented feed can not only improve the feed utilization of juvenile carp,but also promote its digestive capability and will not adversely affect the fillet quality.Experiment 2 Effects of fermented feed on liver antioxidant activity and non-specific immunity of juvenile carp(Cyprinus carpio)This experiment was designed to study the effects of fermented feed on liver antioxidant activity and non-specific immunity of juvenile carp.The design of this experiment and feeding trial were the same as experiment 1.A total of 5 experimental feeds were formulated,including the basal feed(G1),the basal feed supplemented with 2.5%(G2)or 5.0%(G3)of fermented feed,5%(G4)or 10%(G5)of fermented feed substituting the rapeseed meal in basal feed.Three hundred carp,which initial weight was(25.23±0.06)g,were randomly divided into five groups,there were four repetitions in each group,and each group was fed with one kinds of feed.The fish were kept in 20 cages in the same pond,and fed three times daily for 10 weeks.After the feeding trial,blood and liver samples were collected to measure the parameters of plasma physiological and biochemical and liver antioxidant capacity.The results showed that the levels of plasma cortisol and complement C3 of G4 were significantly higher than those of G1(P<0.05),but the activity of myeloperoxidase of G4 was significantly lower than that of G1(P<0.05).And no significant difference was observed in glucose level,total protein content,lysozyme activity and globulin as well as complement C4 contents of plasma(P>0.05).Furthermore,the activities of glutathione peroxidase,catalase and superoxide dismutase as well as the total antioxidant capacity and malondialdehyde contents in liver all showed little difference among all the groups(P>0.05).In conclusion,fermented feed can not only promote the non-specific immune function of the carp,but also has no negative effect on the antioxidant capacity of it.