| Dietary fiber is a general term for a complex mixture,which refers to carbohydrates or analogs that are not easily digested and utilized by the animal body;epidemiological studies believe that dietary fiber can reduce the risk of various diseases,and dietary fiber is also considered to be "the seventh Nutrients".It has been reported in mammalian experiments that cereal dietary fiber can improve diet-induced obesity and metabolic-related diseases.In aquaculture-related studies,it is pointed out that dietary fiber has a negative effect on fish.In the first part of this study,zebrafish was used as the research object,and they were fed with basic feed(Ctrl)and high-fat feed(HFD)for 8 weeks.The results showed that the zebrafish body weight and body weight gain in the high-fat feed group significant increase(P<0.001),feed coefficient(FCR)decreased significantly(P<0.001),compared with the basic feed;zebrafish liver triglyceride(TAG)content in the high-fat diet group increased significantly(P<0.05),lipid droplets increased;indicating high-fat feed will induceds zebrafish to form nutrient fatty liver.In the second part of this study,a zebrafish nutrient fatty liver model was used,and add 5%corn husk fiber(CHF),wheat bran fiber(WBF)and rice bran fiber(RBF)to the high-fat feed.The results showed that three grains fiber can resist the weight gain induced by high-fat feed(P<0.05),the feed coefficient increases(P<0.05),CHF and RBF can reduce the TAG content of zebrafish liver(P<0.05);Zebrafish serum ALT and LPS concentrations increased(P<0.05),and WBF caused zebrafish serum AST concentrations to increase(P<0.05).The results show that CHF and RBF can improve zebrafish nutrient fatty liver.Three cereal fibers can cause zebrafish liver damage under the background of high-fat diet.In the third part of this study,16 s rRNA sequencing was performed on the zebrafish gut microbiota fed the five feeds in the first part and the second part.The results showed that high-fat diet led to a reduction in the alpha-diversity of zebrafish gut microbiota,The relative abundance of Fusobacteriota increased,the relative abundance of Firmicutes and Bacteroidota decreased;the relative abundance of Cetobacterium and Aeromonas increased,and the relative abundance of Bacillus decreased;cereal fiber caused high fat Dietary zebrafish intestinal flora has increased alpha-diversity,relative abundance of Proteobacteria and Firmicutes increased,and relative abundance of Fusobacteriota decreased;corn husk fibers resulted in high-fat diet zebrafish intestinal bacteria The relative abundance of Cetobacterium and Aeromonas is reduced,and the relative abundance of Acinetobacter is increased;wheat bran fiber leads to a relatively high abundance of high-fat diet zebrafish gut bacteria Cetobacterium and Aeromonas;Rice bran fiber reduced the relative abundance of cetaceae Aeromonas of high-fat diet zebrafish intestinal flora,and the relative abundance of Bacillus and Acinetobacter increased.It shows that the three cereal fibers have a negative effect on the intestinal flora under the background of high-fat diet,and the effects of the three cereal fibers on the intestinal flora are different.In the fourth part of this study,under isolated conditions,the isolated indigenous bacteria of fish-Cetobacterium XMX-1,Plesimonas HSX-5,and Aeromonas Veronii XMX-6 As the research object,using three kinds of cereal fiber as the sole carbon source,the ability of three indigenous bacteria to ferment and use three kinds of cereal fiber was analyzed.The results showed that Cetobacterium could ferment and use three kinds of cereal fiber,especially CHF under anaerobic conditions;Plesimonas could ferment and utilize three kinds of cereal fiber under anaerobic or oxygen-limited conditions,and the fermentation and utilization of RBF under anaerobic conditions is poor;Aeromonas Veronii could ferment and utilize three kinds of cereal fiber under anaerobic or oxygen-limited conditions,especially CHFr under oxygen-limited conditions,and the fermentation and utilization of WBF under oxygen-limited conditions is poor.The results showed that the fermentation and utilization of three kinds of cereal fiber by three strains were affected by factors such as fiber type and culture conditions.Through research,it was found that high-fat diets caused zebrafish to produce nutrient fatty liver;adding three kinds of cereal fibers to high-fat diets,it was found that CHF and RBF can improve zebrafish fatty liver induced by high-fat diets,but three kinds of cereal fiber can cause zebrafish liver damage and lead to an increase in the relative abundance of harmful bacteria in the intestinal flora;the effects of the three kinds of cereal fiber on the intestinal flora are different.There are differences in the utilization of fermentation.The reason for the difference may be the difference in the composition of the three cereal fibers.The three cereal fibers have a risk of application to fish in the context of high-fat diets and may be related to intestinal flora. |
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