Microbial compound feed for improving disease resistance of blue crabs and preparation method of microbial compound feed

Abstract

The invention discloses a microbial compound feed for improving disease resistance of blue crabs and a preparation method of the microbial compound feed, and belongs to the technical field of feed preparation. The microbial compound feed comprises the following raw materials in parts by weight: 30-40 parts of fermented soybean meal, 20-25 parts of bran, 15-20 parts of fish meal, 5-8 parts of a compound microbial agent, 3-5 parts of algal polysaccharides, 2-3 parts of a radix astragali extract, 1-2 parts of chitosan, 2-3 parts of a mineral premix and 1-1.5 parts of compound vitamins, wherein the compound microbial agent comprises bacillus licheniformis, lactobacillus acidophilus and saccharomyces cerevisiae. The microbial compound feed disclosed by the invention comprehensively improves the disease resistance of the blue crabs and improves the survival rate through various ways, such as nutrition balance, immune regulation and intestinal health improvement, so that the breeding cost is reduced, and the income of farmers is increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of feed preparation, and particularly relates to a microbial compound feed for improving the disease resistance of mud crabs and a preparation method thereof. Background Art

[0002] As an important economically cultured marine species, mud crabs face many challenges during the farming process, especially the impacts of bacterial diseases and environmental stress. These factors together lead to a relatively low survival rate of mud crabs. To overcome these problems, farmers have taken various countermeasures, but each method has its limitations and potential risks:

[0003] 1. Abuse of antibiotics

[0004] Although the widespread use of antibiotics can control disease outbreaks in the short term, it brings serious side effects. For example, long-term reliance on antibiotics not only accelerates the evolution of pathogen drug resistance but also may lead to antibiotic residues in the water environment, disrupting the ecological balance and affecting the health of non-target organisms. In addition, the abuse of antibiotics will also pollute the aquaculture water quality, further weakening the immunity of mud crabs and forming a vicious cycle.

[0005] 2. Single probiotic feed

[0006] Some farmers have tried to improve the intestinal microbial community structure of mud crabs by adding a single type of probiotic (such as Bacillus or Lactobacillus) in order to improve the disease resistance. However, this method often has limited effects. First, it is difficult for a single strain to stably colonize in the complex intestinal environment, and the protection it provides is relatively short-lived and incomplete. Second, due to the specificity of the functions of different strains, a single probiotic may not be able to meet the needs of mud crabs to resist multiple pathogens, limiting the overall effect of immune enhancement.

[0007] 3. Chemical immune enhancers

[0008] Chemical immune enhancers, such as β-glucan, are used to activate the innate immune system of mud crabs and can theoretically provide effective short-term protection. However, the cost of such substances is relatively high and is not cost-effective for large-scale farming. More importantly, long-term use of chemical immune enhancers may impose a metabolic burden on mud crabs, interfere with normal physiological functions, and may trigger other health problems.

[0009] Therefore, there is an urgent need to provide a microbial compound feed for improving the disease resistance of mud crabs and a preparation method thereof, which can more comprehensively and sustainably improve the health level and disease resistance of mud crabs. Summary of the Invention

[0010] In view of the above technical problems, the present invention provides a microbial compound feed for improving the disease resistance of mud crabs and a preparation method thereof. By means of the synergy among raw materials, a compound microbial inoculant, and an embedding technology for natural immune enhancing factors, the disease resistance of mud crabs is enhanced.

[0011] To achieve the above object, the present invention provides the following technical solutions:

[0012] One of the technical solutions of the present invention:

[0013] A microbial compound feed for improving the disease resistance of mud crabs, by weight, comprises the following raw materials:

[0014] 30 - 40 parts of fermented soybean meal, 20 - 25 parts of wheat bran, 15 - 20 parts of fish meal, 5 - 8 parts of compound microbial inoculant, 3 - 5 parts of seaweed polysaccharide, 2 - 3 parts of astragalus extract, 1 - 2 parts of chitosan, 2 - 3 parts of mineral premix, and 1 - 1.5 parts of compound vitamin;

[0015] Among them, the compound microbial inoculant comprises bacillus licheniformis, lactobacillus acidophilus, and saccharomyces cerevisiae.

[0016] Beneficial effects: The above - mentioned microbial compound feed disclosed by the present invention enhances the disease - resistance ability of mud crabs from multiple aspects through the synergistic effect of various components, including optimizing nutrient supply, improving intestinal health, activating the immune system, and providing necessary trace elements and antioxidant protection. Among them, the combination of fermented soybean meal, fish meal, and wheat bran provides high - quality protein and dietary fiber, promotes intestinal health and nutrient absorption efficiency, and forms a good basic nutrition platform; the beneficial bacteria in the compound microbial inoculant and dietary fiber such as wheat bran form a synergistic effect to jointly build a healthy intestinal microbial community, further enhancing the immune function of mud crabs; both seaweed polysaccharide and astragalus extract are natural immune enhancers, and their combined action can more effectively activate the immune system and improve the overall disease - resistance ability of mud crabs; in addition, the antibacterial property of chitosan and the trace elements provided by the mineral premix not only reduce the presence of pathogenic bacteria but also ensure the balance of trace elements in mud crabs, supporting normal physiological functions.

[0017] Optionally, the particle sizes of the fermented soybean meal and the fish meal are both ≤100 μm.

[0018] Optionally, the mass ratio of bacillus licheniformis, lactobacillus acidophilus, and saccharomyces cerevisiae is 2 - 3∶1 - 2∶1; and in the compound microbial inoculant, the viable count of each strain is ≥1×10 9 CFU / mL.

[0019] Beneficial effects: The compound microbial inoculant with the above - specified specific ratio of the present invention combined with other feed ingredients can achieve the following effects:

[0020] Optimize nutrient absorption: Improve the absorption efficiency of various nutrients in feed by improving intestinal health;

[0021] Enhance immunity: Strengthen the immune system of blue crabs through multiple pathways (such as enzyme production, regulating intestinal pH, and providing immunomodulatory components), making them more resistant to disease;

[0022] Maintaining water quality: Some ingredients, such as Saccharomyces cerevisiae, help purify water, reduce the accumulation of harmful substances, and indirectly support the health of blue crabs;

[0023] Comprehensive benefits: Through the synergistic effects of the above-mentioned aspects, not only can the disease resistance of blue crabs be improved, but also their growth and development can be promoted, ultimately improving the breeding benefits.

[0024] In summary, the above-mentioned microbial compound feed formula defined in the present invention aims to comprehensively improve the immunity of blue crabs and thus improve their survival rate through reasonable ingredient selection and proportion configuration.

[0025] Optionally, the microbial compound feed comprises the following raw materials by weight:

[0026] 40 parts of fermented soybean meal, 20 parts of bran, 15 parts of fish meal, 8 parts of composite microbial agent, 5 parts of seaweed polysaccharide, 3 parts of astragalus extract, 2 parts of chitosan, 3 parts of mineral premix and 1.5 parts of composite vitamins;

[0027] Wherein, the composite microbial agent comprises Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae.

[0028] Optionally, the microbial compound feed comprises the following raw materials by weight:

[0029] 36 parts of fermented soybean meal, 23 parts of bran, 18 parts of fish meal, 7 parts of composite microbial agent, 4 parts of seaweed polysaccharide, 3 parts of astragalus extract, 2 parts of chitosan, 3 parts of mineral premix and 1.5 parts of composite vitamins;

[0030] Wherein, the composite microbial agent comprises Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae.

[0031] Optionally, the microbial compound feed comprises the following raw materials by weight:

[0032] 30 parts of fermented soybean meal, 25 parts of bran, 20 parts of fish meal, 5 parts of composite microbial agent, 3 parts of seaweed polysaccharide, 2 parts of astragalus extract, 1 part of chitosan, 2 parts of mineral premix and 1 part of composite vitamin;

[0033] Wherein, the composite microbial agent comprises Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae.

[0034] Optionally, the mineral premix includes calcium, magnesium, zinc, manganese and selenium, and the mass ratio of each mineral element is 1:1:1:1:1.

[0035] Furthermore, the macro minerals calcium and magnesium in the mineral premix are in the form of inorganic salts, preferably chlorides; zinc, manganese and selenium are trace minerals, which are used as raw materials in the form of amino acid chelates, and the amino acid is preferably glycine.

[0036] Optionally, the astragalus extract is prepared by water extraction method, and the specific steps are as follows:

[0037] According to the solid-liquid ratio of 1 g:10 mL, astragalus powder is added to hot water, stirred and extracted at 60-80 °C for 1-3 hours, and then filtered, concentrated and dried in sequence to obtain the astragalus extract.

[0038] Optionally, the compound vitamin includes vitamin C and vitamin E; the mass ratio of the two is 1-2:1.

[0039] The second technical solution of the present invention:

[0040] A preparation method of a microbial compound feed for improving the disease resistance of green crabs, comprising the following steps:

[0041] Mix fermented soybean meal, bran and fish meal and stir evenly to obtain mixture 1;

[0042] By the embedding method, algal polysaccharide and chitosan are wrapped in a sodium alginate matrix to obtain mixture 2;

[0043] Add mixture 2, astragalus extract, mineral premix, compound vitamin and compound microbial inoculant to the mixture 1 in sequence to obtain mixture 3;

[0044] Add water to the mixture 3 for conditioning, and then carry out granulation and drying treatments in sequence to prepare the microbial compound feed.

[0045] Beneficial effects: Through reasonable raw material selection, advanced embedding technology and fine processing, the present invention successfully prepares a highly efficient and multifunctional microbial compound feed, significantly improving the disease resistance and overall health level of green crabs.

[0046] Optionally, the specific process of the embedding method is as follows:

[0047] Add algal polysaccharide and chitosan to a sodium alginate solution (2 wt.% - 4 wt.%) to obtain a mixed solution; then mix the mixed solution and a calcium chloride solution (2 wt.% - 4 wt.%) for curing for 10-20 min to form a stable microcapsule structure, and then carry out spray drying.

[0048] Beneficial effects: The present invention adopts the microcapsule embedding technology to wrap algal polysaccharides with significant immunomodulatory functions and chitosan in a sodium alginate matrix. By this method, not only can these active ingredients be protected from the influence of the external environment (such as temperature, humidity, pH value changes, etc.), but also their stability and bioavailability in the feed can be improved. The final product is processed by spray drying to control the particle size, which is suitable for efficiently feeding mud crabs.

[0049] Furthermore, the mass ratio of the sum of the algal polysaccharides and chitosan to the sodium alginate solution is: 1∶12 - 15.

[0050] Furthermore, the particle size of the particles after the spray drying treatment is 50 - 80 μm.

[0051] Optionally, during the water conditioning process, the addition amount of water is 15 - 20 wt.% of the total raw materials (fermented soybean meal, wheat bran, fish meal, compound microbial inoculum, algal polysaccharides, astragalus extract, chitosan, mineral premix, and compound vitamins).

[0052] Optionally, the particle size of the particles obtained during the granulation process is 1 - 3 mm.

[0053] Optionally, the drying process is: drying at a temperature of 35 - 50 °C until the moisture content < 10%.

[0054] Compared with the prior art, the present invention has the following advantages and technical effects:

[0055] The microbial compound feed prepared by the present invention comprehensively improves the disease resistance of mud crabs through various ways (such as balanced nutrition, immunomodulation, improvement of intestinal health, etc.), increases the survival rate, and thus reduces the breeding cost and increases the income of farmers.

[0056] The present invention reduces the pollution of the water quality by feed residues through scientific formula and process design, and protects the ecological environment. Detailed embodiments

[0057] Now, the various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0058] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0059] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0060] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0061] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0062] The embodiments of this invention provide a microbial compound feed for improving the disease resistance of mud crabs, which comprises the following raw materials by weight parts:

[0063] 30 - 40 parts of fermented soybean meal, 20 - 25 parts of wheat bran, 15 - 20 parts of fish meal, 5 - 8 parts of compound microbial inoculum, 3 - 5 parts of seaweed polysaccharide, 2 - 3 parts of astragalus extract, 1 - 2 parts of chitosan, 2 - 3 parts of mineral premix and 1 - 1.5 parts of compound vitamin; wherein, the compound microbial inoculum includes bacillus licheniformis, lactobacillus acidophilus and saccharomyces cerevisiae.

[0064] In the embodiments of this invention, wheat bran is a by-product of wheat flour processing, mainly composed of the outer shell of wheat, and is rich in dietary fiber, protein, vitamin B group, minerals and antioxidants.

[0065] In the embodiments of this invention, fish meal is a high-protein feed raw material, which is processed from one or more kinds of fish through defatting, dehydrating and pulverizing.

[0066] In the embodiments of this invention, bacillus licheniformis reduces the oxygen concentration in the intestine through biological oxygen deprivation, thereby promoting the proliferation of anaerobic probiotics and inhibiting the growth of aerobic pathogenic bacteria (such as escherichia coli, vibrio). These probiotics secrete enzymes such as protease, lipase, amylase, etc., which help to decompose macromolecular substances in the feed, thereby improving the apparent digestibility of phosphorus, reducing the bait coefficient, and producing antibacterial substances such as bacitracin and lysozyme.

[0067] In the embodiments of the present invention, Lactobacillus acidophilus can activate the immune system, promote the secretion of immunoglobulins and cytokines, thereby enhancing the non-specific immune response. It forms a protective barrier by adhering to the intestinal mucosa, effectively blocking the invasion path of pathogens, and then improving the disease resistance of the body. In addition, Lactobacillus acidophilus can also decompose organic substances in residual baits and feces, reduce the accumulation of ammonia nitrogen, and contribute to maintaining the stability of the water ecosystem.

[0068] In the embodiments of the present invention, Saccharomyces cerevisiae is a high-quality feed protein source because it is rich in protein, B vitamins, and essential amino acids. It can promote the weight gain of aquatic animals. At the same time, β-1,3-glucan and mannan oligosaccharides contained in the yeast cell wall can stimulate the activity of macrophages, thereby enhancing the resistance to viruses.

[0069] In some preferred embodiments of the present invention, the mass ratio of Bacillus licheniformis, Lactobacillus acidophilus, and Saccharomyces cerevisiae is 2-3∶1-2∶1; and in the composite microbial inoculant, the viable count of each strain ≥ 1×10 9 CFU / mL.

[0070] In the alternative embodiments of the present invention, the particle sizes of fermented soybean meal and fish meal are both ≤ 100 μm.

[0071] In the alternative embodiments of the present invention, the astragalus extract is prepared by the water extraction method. The specific steps are as follows: According to the solid-liquid ratio of 1 g∶10 mL, astragalus powder is added to hot water, stirred and extracted at 60-80 °C for 1-3 hours, and then filtered, concentrated, and dried in sequence to prepare the astragalus extract.

[0072] The preparation method of the biological composite feed in the embodiments of the present invention includes the following steps: Mix fermented soybean meal, wheat bran, and fish meal, and stir evenly to obtain mixture 1; Using the embedding method, encapsulate algal polysaccharide and chitosan in the sodium alginate matrix to obtain mixture 2; Add mixture 2, astragalus extract, mineral premix, compound vitamin, and composite microbial inoculant to mixture 1 in sequence to obtain mixture 3; Add water to mixture 3 for conditioning, and then perform granulation and drying treatments in sequence to prepare the microbial composite feed.

[0073] In the alternative embodiments, the specific process of the embedding method is as follows: Add algal polysaccharide and chitosan to the sodium alginate solution (2 wt.%-4 wt.%) to obtain a mixed solution; Then mix the mixed solution and calcium chloride solution (2 wt.%-4 wt.%) for curing for 10-20 min to form a stable microcapsule structure, and then perform spray drying.

[0074] In the embodiments of the present invention, the "room temperature" mentioned herein, unless otherwise specified, all refers to 20-30 °C.

[0075] All raw materials used in the embodiments of the present invention are obtained by purchasing on the market. Bacillus licheniformis is purchased from Shandong Xinxiong Biotechnology Co., Ltd., Lactobacillus acidophilus is purchased from Jiangsu Green Science Biotechnology Co., Ltd., and Saccharomyces cerevisiae is purchased from Shandong Yihao Biotechnology; the macro minerals calcium and magnesium are in the form of chlorides; zinc, manganese and selenium are in the form of glycine chelates.

[0076] The technical solution of the present invention will be further described below through embodiments.

[0077] Example 1

[0078] A preparation method of a microbial compound feed for improving the disease resistance of mud crabs includes the following steps:

[0079] (1) Weigh the following raw materials for standby according to parts by weight:

[0080] 40 parts of fermented soybean meal, 20 parts of wheat bran, 15 parts of fish meal, 8 parts of compound microbial inoculant, 5 parts of seaweed polysaccharide, 3 parts of astragalus extract, 2 parts of chitosan, 3 parts of mineral premix (calcium, magnesium, zinc, manganese and selenium, and the mass ratio of each mineral element is 1:1:1:1:1), and 1.5 parts of compound vitamin (vitamin C and vitamin E; the mass ratio of the two is 2:1);

[0081] Among them, the compound microbial inoculant includes Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae, and the mass ratio of the three is 3:2:1. And in the compound microbial inoculant, the viable count of each strain ≥ 1×10 9 CFU / mL;

[0082] The astragalus extract is prepared by water extraction method, and the specific steps are as follows:

[0083] According to the solid-liquid ratio of 1 g:10 mL, add astragalus powder to hot water, stir and extract at 70 °C for 2 hours, and then filter, concentrate and dry in sequence to obtain the astragalus extract;

[0084] (2) Mix the fermented soybean meal, wheat bran and fish meal, and stir evenly to obtain mixture 1;

[0085] (3) Adopt the embedding method to wrap the seaweed polysaccharide and chitosan in the sodium alginate matrix to obtain mixture 2;

[0086] Among them, the specific steps of the embedding method are as follows:

[0087] The mass ratio of the sum of algal polysaccharide and chitosan to the sodium alginate solution is 1:15. The algal polysaccharide and chitosan are added to the sodium alginate solution (2 wt.%) to obtain a mixed solution. Then, the mixed solution is mixed with a calcium chloride solution (2 wt.%) and solidified for 15 min to form a stable microcapsule structure, and then spray-dried to obtain particles with a particle size of 50 - 80 μm;

[0088] (3) To the mixture 1, the mixture 2, astragalus extract, mineral premix, compound vitamin, and compound microbial inoculant are added in sequence to obtain a mixture 3;

[0089] (4) The mixture 3 is conditioned with 15 wt.% of water, and then granulated (particle size of 1 - 3 mm) and dried (dried at 45 °C until the moisture content < 10%) in sequence to prepare a microbial compound feed.

[0090] Example 2

[0091] The difference from Example 1 is that

[0092] In step (1), the microbial compound feed, by weight, comprises the following raw materials:

[0093] 36 parts of fermented soybean meal, 23 parts of wheat bran, 18 parts of fish meal, 7 parts of compound microbial inoculant, 4 parts of algal polysaccharide, 3 parts of astragalus extract, 2 parts of chitosan, 3 parts of mineral premix, and 1.5 parts of compound vitamin;

[0094] Other preparation conditions are the same as those in Example 1.

[0095] Example 3

[0096] The difference from Example 1 is that

[0097] In step (1), the microbial compound feed, by weight, comprises the following raw materials:

[0098] 30 parts of fermented soybean meal, 25 parts of wheat bran, 20 parts of fish meal, 5 parts of compound microbial inoculant, 3 parts of algal polysaccharide, 2 parts of astragalus extract, 1 part of chitosan, 2 parts of mineral premix, and 1 part of compound vitamin;

[0099] Other preparation conditions are the same as those in Example 1.

[0100] Example 4

[0101] The difference from Example 1 is that

[0102] In step (1), the compound microbial inoculant comprises Bacillus licheniformis, Lactobacillus acidophilus, and Saccharomyces cerevisiae, and the mass ratio of the three is 3:1:1.

[0103] Other preparation conditions are the same as those in Example 1.

[0104] Example 5

[0105] The difference from Example 1 is that

[0106] In step (1), the compound microbial inoculum includes Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae, and the mass ratio of the three is 2∶1∶1.

[0107] Other preparation conditions are the same as those in Example 1.

[0108] Comparative Example 1

[0109] The difference from Example 1 is that in step (1), Saccharomyces cerevisiae is not added to the compound microbial inoculum; other preparation conditions are the same as those in Example 1.

[0110] Comparative Example 2

[0111] The difference from Example 1 is that in step (1), astragalus extract is not added to the raw materials; other preparation conditions are the same as those in Example 1.

[0112] Comparative Example 3

[0113] The difference from Example 1 is that in step (1), mineral premix is not added to the raw materials; other preparation conditions are the same as those in Example 1.

[0114] Comparative Example 4

[0115] The difference from Example 1 is that in step (3), chitosan is not added; other preparation conditions are the same as those in Example 1.

[0116] Comparative Example 5

[0117] The difference from Example 1 is that in step (3), seaweed polysaccharide is not added; other preparation conditions are the same as those in Example 1.

[0118] Effect verification

[0119] Select juvenile Scylla serrata with consistent specifications (about 20 grams in weight per juvenile crab), full individuals and strong vitality and put them into eleven test areas with the same environment. 100 juvenile crabs are put into each test area, and they are respectively fed with equal amounts of basic feed (Segelin, Qingdao, as the control group), feed prepared in Examples 1-5 or Comparative Examples 1-5 (each test area is fed according to the conventional feeding amount for Scylla serrata breeding). After five months of breeding, they are harvested collectively, and the average weight and survival rate of Scylla serrata in each test area are counted. The results are shown in Table 1.

[0120] Table 1

[0121]

[0122] Summary: By comparing the above effect data, it can be seen that the feeds in all examples significantly increased the average weight and survival rate of Scylla serrata, showing obvious improvements compared with the control group and comparative examples. Among them, the feed in Example 1 performed best, leading not only in average weight but also achieving the highest survival rate of 96%. In addition, the compound bacterium agent composed of Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae is crucial for improving the growth and survival rate of mud crabs. After missing some strains or not adding astragalus extract and mineral premix, the average weight and survival rate of mud crabs decreased significantly, indicating that it plays an important role in enhancing immune function and promoting growth. Moreover, after removing chitosan and seaweed polysaccharide in Comparative Examples 4 and 5 respectively, the average weight and survival rate also decreased significantly, indicating that the two have a synergistic effect in protecting active ingredients and enhancing immunity.

[0123] In summary, the microbial compound feed prepared in the examples of the present invention has significant effects in improving the growth performance and survival rate of mud crabs, and there is a synergistic effect among the components, jointly promoting the health and productivity of mud crabs.

[0124] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A microbial compound feed for improving the disease resistance of blue crabs, characterized in that: The following raw materials are included by weight: 30-40 parts of fermented soybean meal, 20-25 parts of bran, 15-20 parts of fish meal, 5-8 parts of composite microbial agent, 3-5 parts of seaweed polysaccharide, 2-3 parts of astragalus extract, 1-2 parts of chitosan, 2-3 parts of mineral premix and 1-1.5 parts of composite vitamins; Wherein, the composite microbial agent comprises Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae.

2. The microbial compound feed for improving the disease resistance of blue crab according to claim 1, characterized in that: The mass ratio of the Bacillus licheniformis, Lactobacillus acidophilus and Saccharomyces cerevisiae is (2-3):(1-2):

1.

3. The microbial compound feed for improving the disease resistance of blue crab according to claim 1, characterized in that: The mineral premix includes calcium, magnesium, zinc, manganese and selenium, and the corresponding mass ratio of each mineral element is 1:1:1:1:

1.

4. The microbial compound feed for improving the disease resistance of blue crab according to claim 1, characterized in that: The astragalus extract is prepared by water extraction, and the specific steps are as follows: The astragalus powder is added into hot water, and the mixture is stirred and extracted at 60-80° C. for 1-3 hours, and then filtered, concentrated and dried in sequence to prepare the astragalus extract.

5. The microbial compound feed for improving the disease resistance of blue crab according to claim 1, characterized in that: The compound vitamin comprises vitamin C and vitamin E; the mass ratio of the two is 1-2:

1.

6. A method for preparing a microbial compound feed for improving the disease resistance of blue crabs, characterized in that: The following steps are involved: Weigh the weight portions of the raw materials according to any one of claims 1 to 5 for later use; Mixing fermented soybean meal, bran and fish meal, and stirring evenly to obtain a mixture 1; Using the embedding method, seaweed polysaccharide and chitosan are encapsulated in a sodium alginate matrix to obtain a mixture 2; Adding mixture 2, astragalus extract, mineral premix, composite vitamins and composite microbial agent to mixture 1 in sequence to obtain mixture 3; Water is added to the mixture 3 for conditioning, and then granulation and drying are performed in sequence to prepare the microbial compound feed.

7. The method for preparing a microbial compound feed for improving the disease resistance of blue crabs according to claim 6, characterized in that: The specific process of the embedding method is as follows: adding seaweed polysaccharide and chitosan into sodium alginate solution to obtain a mixed solution; Then the mixed solution and the calcium chloride solution are mixed and solidified to form a stable microcapsule structure, and then spray-dried.

8. The method for preparing a microbial compound feed for improving the disease resistance of blue crabs according to claim 7, characterized in that: The mass ratio of the sum of the mass of the seaweed polysaccharide and the chitosan to the mass of the sodium alginate solution is 1:12-15.

9. The method for preparing a microbial compound feed for improving the disease resistance of blue crabs according to claim 6, characterized in that: During the water-adding and conditioning process, the amount of water added is 15-20 wt.% of the total raw materials.

10. The method for preparing a microbial compound feed for improving the disease resistance of blue crabs according to claim 6, characterized in that: The drying process is: drying at a temperature of 35-50° C. until the moisture content is less than 10%.

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