Nutritional And Physiological Response Of Dietary Fiber Of Largemouth Bass

Dietary fiber is known as the"seventh nutrient"and has not been valued by many people before.Many studies believe that it is an anti-nutrition factor,but with the advancement of science,many studies have shown that dietary fiber has a positive role in nutritional regulation,and It also has the effect of regulating the balance of intestinal flora and improving intestinal health.Unfortunately,monogastric animals(fish)have a low utilization rate of fiber,and due to the changing trend of fish feed formulas and the constraints of animal protein resources,plant ingredients are always added to the feed,and the fiber also increases.As we all know,too much fiber in the feed will cause adverse effects on aquatic animals.Therefore,this experiment was aimed at largemouth bass,and its growth performance,nutrition utilization,blood parameters,intestinal health,and liver function were evaluated by studying different fiber levels and different fiber sources.Under the circumstances,to determine the tolerance status of the largemouth bass to fiber levels and fiber types,it provides technical information for the rational use of plant protein materials and optimization of largemouth bass feed formula.1.Nutritional and physiological response of dietary fiber levels of largemouth bassThe basic feed add 0%,7%,14%,21%,and 28%of bean dregs and the fiber content is five gradient levels of 1.24%,3.43%,5.12%,6.95%and 8.50%,respectively.An experimental feed of isonitrogenous and isolipidic,and cultured for 60 days.The results showed that low fiber did not affect the growth performance of largemouth bass,but high fiber(8.50%)feed had a negative impact on the growth performance of largemouth bass,and the optimal fiber level was about 4.07%.Fiber level has a significant effect on body composition,and hepatopancreas somatic index(HSI),viscera somatic index(VSI)and mesenteric fat index(MFI)decrease significantly as feed fiber levels increase(P<0.05).At the same time,the contents of triglyceride(TG)and total cholesterol(TC)in plasma of largemouth bass decreased significantly with the increase of feed fiber level(P<0.05).In addition,the aspartate aminotransferase(AST)of 1.24%fiber level group was significantly higher than other groups(P<0.05).Feed fiber levels have a significant effect on the gut health of largemouth bass.Among them,the large intestine antioxidant indexes superoxide dismutase(SOD),catalase(CAT),nitric oxide synthase(NOS),amylase(AMS),Na~+,K~+-ATPase activity and total protein(TP)content decreased significantly with the increase of fiber level,while the malondialdehyde(MDA)content showed the opposite trend(P<0.05).From the intestinal section,it can be found that with the increase of fiber level,the number of goblet cells in the hindgut of largemouth bass gradually decreases,the height of intestinal villi gradually becomes shorter,and the intestinal villi are relatively sparse.It was found from the intestinal flora that the number and variety of species in the medium fiber group were rich,and that beneficial bacteria were found to occupy a certain proportion.In addition,the dietary fiber level also significantly affected the liver function of largemouth bass.The antioxidant index SOD,CAT and NOS activities increased with the increase of fiber level,while MDA showed the opposite trend(P<0.05).Carnitine palmitoyl transferase 1(CPT-1),peroxisome proliferator-activated receptor?(PPAR-?)and Adenosine 5-monophosphate activated protein kinase(AMPK)activities were significantly increased with the increase of fiber level(P<0.05).At the same time,it was also found that the liver at 1.24%fiber level was not full and whitish.From the liver tissue section,it was found that compared with other groups,the 1.24%fiber group had a heavier outline of liver cells,hepatocyte vacuolation was more serious,and the hepatocyte nuclei gradually dissolved or missing.As can be seen,the fiber(<8.5%)in the feed does not affect the growth,but the addition of fiber over 8.5%will inhibit the growth,and its optimum addition amount is 4.07%.In addition,the addition of fiber to the feed does have the effect of lowering blood lipids and cholesterol,which can improve liver function,but it will have a negative impact on intestinal health.Therefore,it is important to add the right amount of fiber to the feed,but it should not be added blindly or not,because too high or too low the fiber in the feed will negatively affect the largemouth bass.2.Nutritional and physiological response of dietary fiber source of largemouth bassIn order to investigate the nutritional and physiological response of largemouth bass to dietary fiber sources,this study added 5.2%fiber dregs(DF),fermented soybean dregs(FF)and carboxymethyl cellulose(CF)and microcrystalline cellulose(MF)and conFig.ured into an experimental feed of equal nitrogen and fat,and cultured for 60 days.The results showed that the weight gain rate(WGR),specific growth rate(SGR)and protein efficiency ratio(PER)of the CF group were significantly lower than those of the other groups.The opposite trend(P<0.05).In addition,the dietary fiber source will affect the plasma biochemical indexes of largemouth bass.Among them,the Alanine aminotransferase(ALT),AST and alkaline phosphatase(ALP)activity and TG content were significantly higher than other groups(P<0.05).In order to evaluate the effect of feed fiber sources on intestinal health,we evaluated the intestinal antioxidant and intestinal sections and intestinal microorganisms.The SOD,CAT,AMS and Na~+,K~+-ATPase activities of CF group were significantly lower than those of FF and In the MF group,the contents of MDA were significantly higher than those in the other experimental groups(P<0.05),while the NO content in the FF group was significantly higher than in the other experimental groups(P<0.05).In addition,we found that the intestinal villi of the largemouth bass fed the CF group showed sparse intestinal villi,short intestinal villi length,and severe vacuolation,and other degenerative changes.In addition,the intestinal microorganisms in the CF group were mainly pathogenic bacteria,and Among intestinal microorganisms in FF group,beneficial bacteria such as Lactobacillus and Bacillus accounted for a certain proportion.In addition,we also evaluated liver function and found that SOD and CAT activities and TP and nitric oxide(NO)contents in CF group were significantly lower than those in other groups,while MDA contents were significantly higher than those in other groups(P<0.05).The liver lipid meTab.olism indexes CPT-1,PPAR-?and AMPK in CF group were significantly lower than those in other groups(P<0.05).In addition,the livers of largemouth bass fed with CF feed had a whitish appearance,blurred outline of liver cell morphology,severe hepatocyte vacuolization,gradual dissolution or loss of hepatocyte nuclei,and hepatocyte cords were not obvious.It can be seen that the addition of 5.2%carboxymethyl cellulose in the feed can destroy the liver and intestine health of the bigmouth bass,thus inhibiting its growth,revealing that the tolerance of the bigmouth bass to CF in the feed is extremely poor,and the addition of 5.2%FF in the feed can promote its growth.Therefore,in the process of research and development of largemouth bass feed,the appropriate amount of fermented soybean dregs can be considered as raw materials,but the content of carboxymethyl fiber in the feed should be strictly controlled.