The Effects Of Dietary Cellulose On Nutritional Physiological Functions For Juvenile Yellow Catfish,Pelteobagrus Fulvidraco

The success and sustainability of aquaculture depend on the cost of feed operation.As the main feed raw material fishmeal is expensive,more and more attention has been paid to the addition of plant-derived substances to fish feed.However,one of the main factors restricting the utilization of plant components is the inevitable introduction of more fibers.Cellulose and other fibrous carbohydrates are found in the structural components of plants and cannot be digested by fish.In recent years,dietary fiber has attracted much attention because of its important role in growth,intestinal health,and other physiological effects.The yellow catfish(Pelteobagrus fulvidraco)is one of the most important economically farmed fish in southern China.To our knowledge,no previous studies have demonstrated the role of dietary cellulose in regulating the growth and health of yellow catfish.Therefore,based on long-term research on aquatic animal nutrition and immunology,this study explored the nutritional physiological effects of dietary cellulose on juvenile yellow catfish.The specific studies are as follows:1.Many studies have shown that the intestinal cellulase activity of aquatic animals may come from microorganisms in the digestive tract.To explore the relationship between feed cellulose and fish intestinal flora.In this experiment,antibiotics were used to simulate the dynamic process of intestinal flora imbalance to explore the physiological response of yellow catfish to feed cellulose.Four experimental diets containing two cellulose levels(0% and 10%)and two antibiotic levels(control and antibiotic groups)were formulated using a 2 × 2 two-factor experimental design.The experimental period was 84 days.The results showed that the weight gain(WG)and specific growth rate(SGR)of experimental fish in the antibiotic group were significantly lower than those in the control group,while the WG and SGR in the control group were significantly higher than those in the control group.The contents of serum total protein(TP),albumin(ALB),and globulin(GLO)in the antibiotic group were significantly lower than those in the control group,while the activities of glutamic oxaloacetic transaminase(AST)and glutamic pyruvic transaminase(ALT)in the antibiotic group were significantly higher than those in the control group.The contents of TP and GLO in the experimental fish fed with a 10% cellulose diet in the control group and antibiotic group were significantly increased.The contents of serum complement 3(C3),complement 4(C4),immunoglobulin G(Ig G),and lysozyme(LZM)activity in the antibiotic group were significantly lower than those in the control group,while the levels of serum C3 and Ig G in the control group were significantly higher than those in the control group,while the immune reaction parameters in the antibiotic group were not affected by the level of cellulose.The m RNA expression of TNF,IL1 and IL 8 genes in the intestinal tract of the experimental fish in the antibiotic group was significantly higher than that in the control group,while the m RNA expression of TNF and IL 1genes in the intestinal tract of the experimental fish fed with 10% cellulose diet in the control group was up-regulated,while the inflammatory factor-related genes in the antibiotic group were not affected by the level of cellulose addition.The results showed that the imbalance of intestinal flora led to the deterioration of serum biochemical indexes of yellow catfish,the expression of inflammation-related gene m RNA was significantly up-regulated,and further led to the decline of growth performance and immunity.Dietary cellulose supplementation can affect the health status of yellow catfish to some extent.However,the appropriate amount of dietary cellulose for yellow catfish needs to be studied.2.To further study the appropriate dietary cellulose levels of yellow catfish and analyze the effects of different cellulose levels on its intestinal flora.Four experimental diets were formulated to contain four cellulose levels(0,5,10,and 15% of dry diet)by adding microcrystalline cellulose.The experimental period was 84 days.The results showed that the growth performance [final body weight(FBW)and WG],serum biochemical parameters [TP,GLO,and ALB],and intestinal trypsin activity of experimental fish in the 5% cellulose group were significantly higher than those of the other treatment groups.Conversely,high cellulose levels(15%)were associated with lower WG,increased serum AST,ALT activities,and higher intestinal cellulase activity.Besides,the core intestinal microbiota is not affected by dietary cellulose levels,but its abundance is significantly affected to some extent.Fish fed a 5% cellulose diet significantly increasing the richness of Fimicutes,Bacteroidetes,and Cetobacterium,yet the higher richness of Proteobacteria,Pseudomonas,and Acinetobacter were detected in fish fed 10 and 15% cellulose diets.We could be concluded that moderate dietary cellulose(5%)supplementation was beneficial to promoting the growth and intestinal health of fish through serum biochemical parameters,intestinal digestive enzyme activity effects,which could be at least part of the reason is the regulation of intestinal microbiota.3.The relationship between dietary fiber levels and protein requirements in fish has not been deeply studied.The purpose of this study was to study the interaction of dietary cellulose and protein in regulating the growth and health status of yellow catfish.Nine experimental diets containing three protein levels(40%,45%,and 50%)and three cellulose levels(0%,5%,and 10%)were formulated using a 3 × 3 two-factor experimental design.Each diet was fed to yellow catfish for 84 days.The results indicated that fish fed diets containing 45%and 50%protein had higher WG than that fish fed a 40%protein diet,while fish fed diets supplemented with 5%cellulose achieved the greatest WG and the lower FCR.We found that as dietary cellulose and protein levels were increased,the activities of antioxidant enzymes[superoxide dismutase(SOD),catalase(CAT)and glutathione peroxidase(GPx)],immune response parameters[alkaline phosphatase(AKP),acid phosphatase(ACP),phagocytic index(PI),respiratory burst(RB),C 3 and 4]and the m RNA level expression of copper/zinc superoxide dismutase(Cu/Zn-SOD),CAT,GPx and glutathione reductase(GR)all rose.On the contrary,rising cellulose levels were associated with decreased malondialdehyde contents and increasing TNF,IL 1,and IL 8 m RNA expression.We can conclude that dietary protein supplements can enhance the immune function of yellow catfish.Although the effect of dietary protein on the immune response is affected by dietary cellulose level,the increase of dietary cellulose is related to the up-regulation of inflammatory genes.