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

Abstract

The invention discloses a compound feed for improving disease resistance of blue crabs and a preparation method of the compound feed, and belongs to the technical field of aquaculture feeds. The compound feed capable of improving the disease resistance of the blue crabs comprises the following raw materials in parts by mass: 25-35 parts of soybean meal, 15-25 parts of peanut meal, 15-20 parts of fish meal, 4-6 parts of a compound microbial agent, 10-12 parts of wheat flour, 4-6 parts of chicory root powder, 4-6 parts of oat flour, 1.5-2.5 parts of corncob zymolyte, 0.5-1 part of compound vitamins, 1-1.5 parts of compound mineral salt and 2-4 parts of a traditional Chinese medicine composition. The compound feed disclosed by the invention can be used for improving the disease resistance of the blue crabs and reducing the use of antibiotic drugs; and the compound feed can improve the growth performance and survival rate of the blue crabs, achieves the purpose of yield increase, and has good popularization and application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aquaculture feed, in particular to a compound feed for improving the disease resistance of mud crab and a preparation method thereof. BACKGROUND

[0002] The genus Scylla includes four species, namely Scylla paramamosain, Scylla serrata, Scylla tranquebarica and Scylla olivacea. Scylla paramamosain is the largest and fastest-growing valuable marine crab, and is one of the traditional export aquatic products and main breeding varieties. It has high nutritional value and is known as the sea ginseng, and is a precious seafood that is deeply welcomed by people. Mud crab has strong disease resistance, can tolerate dry exposure, and adult individuals are suitable for long-distance transportation, so its sales market is stable.

[0003] In recent years, due to climate change, water quality deterioration and other reasons, combined with the fact that the problems of high-quality seed cultivation, healthy breeding and commercial feed for mud crab have not been effectively solved, the disease problem of mud crab is more serious. Antibacterial drugs are commonly used drugs for fish disease prevention and control in recent years, and play an important role in preventing and treating bacterial infectious diseases. Although a wide range of antibiotics are used for water disease prevention and control, the use of some antibiotics that have potential harm to the environment and human health has seriously affected the quality of aquatic products and the reputation of products. In addition, research has found that antibiotics have a certain inhibitory effect on the immune function of animals, which can easily cause the animal body to be low in immunity, reduce the immune function against infection, and even inhibit the growth of animals. In addition, the wide application of various antibiotics in aquaculture has also caused serious mutation of drug-resistant strains, increased the cost of disease drug prevention and control, and increased the incidence of various diseases year by year. Therefore, it is urgent to find a method to improve the disease resistance of mud crab to reduce the amount of antibacterial drugs. SUMMARY

[0004] The purpose of the present application is to provide a compound feed for improving the disease resistance of mud crab and a preparation method thereof to solve the problems existing in the prior art.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] One of the technical solutions of the present invention is a compound feed for improving the disease resistance of mud crabs, comprising the following raw materials in parts by weight: 25-35 parts soybean meal, 15-25 parts peanut meal, 15-20 parts fish meal, 4-6 parts compound microbial agent, 10-12 parts wheat flour, 4-6 parts chicory root powder, 4-6 parts oat flour, 1.5-2.5 parts corn cob enzymatic hydrolysate, 0.5-1 part compound vitamins, 1-1.5 parts compound mineral salts, and 2-4 parts traditional Chinese medicine composition.

[0007] Wheat flour contains water-soluble dietary fiber and functional oligosaccharides, chicory root powder contains fructooligosaccharides, oat flour contains β-glucan, and corn cob hydrolysate contains xylooligosaccharides. These components all promote the growth and reproduction of microorganisms, enabling beneficial microorganisms to colonize in the intestines of mud crabs, regulating the intestinal microecological balance of mud crabs, inhibiting the colonization of harmful bacteria, and enhancing immune function and disease resistance of mud crabs.

[0008] Furthermore, the compound microbial agent comprises the following components in parts by weight: 6-8 parts of Bifidobacterium longum, 4-6 parts of Lactobacillus reuteri, and 2-4 parts of Bacillus licheniformis.

[0009] Bifidobacterium longum can inhibit the proliferation of harmful bacteria such as Vibrio and Escherichia coli by competing for nutrients and mucosal attachment sites, thereby increasing the abundance of beneficial bacteria and reducing the risk of gut microbiota imbalance. Bifidobacterium longum can also secrete short-chain fatty acids, providing energy for the intestinal epithelial cells of mud crabs, promoting mucosal cell proliferation and repair, and reducing the incidence of intestinal inflammation.

[0010] Lactobacillus reuteri can enhance the non-specific immune function of mud crabs, secrete organic acids such as lactic acid and acetic acid, lower the intestinal pH value, and disrupt the stability of harmful bacteria cell membranes.

[0011] Bacillus licheniformis can produce antimicrobial peptides and hydrogen peroxide, which inhibit the proliferation of harmful bacteria. At the same time, it can form spore structures that are resistant to gastric acid and high temperature, and continue to exert their effects after germination in the intestines of mud crabs.

[0012] The combined use of Bifidobacterium longum, Lactobacillus reuteri, and Bacillus licheniformis can fully occupy the intestinal ecological niche and effectively inhibit harmful bacteria; it can regulate intestinal health and immune function, reduce the impact of diseases on growth, and form a virtuous cycle of "nutrient absorption - immune enhancement - growth improvement".

[0013] Furthermore, the method for preparing the corn cob enzymatic hydrolysate includes the following steps:

[0014] Corn cobs are ground to obtain corn cob powder;

[0015] Corn cob powder is added to water, steamed and then cooled. A compound enzyme is added for enzymatic hydrolysis. After enzyme inactivation, the mixture is filtered, and the filtrate is concentrated and dried to obtain the corn cob enzymatic hydrolysate.

[0016] Furthermore, the ratio of corn cob powder to water is 1g:12~15mL;

[0017] The cooking temperature is 95~105℃, and the time is 1~1.5h.

[0018] Furthermore, the complex enzyme comprises xylanase and cellulase in a mass ratio of (2~4):1;

[0019] The amount of the compound enzyme added is 0.5-0.7% of the mass of water;

[0020] The conditions for enzymatic hydrolysis include: ultrasonic power of 250~300W, temperature of 45~50℃, and time of 20~40min.

[0021] Further, the complex vitamin comprises the following components in parts by weight: 10-15 parts vitamin A, 5-8 parts vitamin B1, 20-25 parts vitamin B6, 40-50 parts vitamin C, 20-25 parts vitamin D3, 40-50 parts vitamin E, and 10-15 parts folic acid.

[0022] Further, the composite mineral salt comprises the following components in parts by mass: 5-8 parts potassium dihydrogen phosphate, 10-12 parts ferric citrate, 4-6 parts manganese sulfate, 1-2 parts magnesium sulfate heptahydrate, 0.2-0.5 parts copper sulfate pentahydrate, 0.3-0.6 parts zinc sulfate, and 10-12 parts potassium chloride.

[0023] Furthermore, the traditional Chinese medicine composition comprises the following raw materials in parts by weight: 2-3 parts honeysuckle, 4-6 parts isatis root, 5-8 parts dandelion, and 4-6 parts houttuynia cordata.

[0024] Honeysuckle, isatis root, dandelion, and houttuynia cordata contain flavonoids, alkaloids, polysaccharides, volatile oils, and other substances that can exert antibacterial, anti-inflammatory, and immunomodulatory effects. The combined use of these four substances in mud crab farming can reduce the incidence of diseases, enhance the stress resistance of mud crabs, and improve their growth performance.

[0025] The second technical solution of the present invention: a method for preparing the above-mentioned compound feed for improving the disease resistance of mud crabs, comprising the following steps:

[0026] The raw materials for the compound feed that improves the disease resistance of mud crabs are mixed evenly and granulated to obtain the compound feed that improves the disease resistance of mud crabs.

[0027] Furthermore, when the compound feed is used for juvenile crabs, the particle size of the granulation is 0.5~1.5mm;

[0028] When the compound feed is used for adult crabs, the granulation particle size is 1.5~3.5mm.

[0029] The present invention discloses the following technical effects:

[0030] The compound feed of this invention can improve the disease resistance of mud crabs and reduce the use of antibiotics.

[0031] The compound feed of this invention can improve the growth performance and survival rate of mud crabs, thereby increasing production and has good prospects for promotion and application. Detailed Implementation

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0035] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0036] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0037] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0038] I. Biological characteristics of mud crabs

[0039] Mud crabs are distributed in temperate, subtropical, and tropical seas. They particularly prefer to inhabit river estuaries or shallow bays. The genus *Scylla* contains four species: *Scylla paramamosain*, *Scylla serrata*, *Scylla tranquebarica*, and *Scylla olivacea*.

[0040] The external morphology of juvenile and adult mud crabs is divided into three parts: the cephalothorax, abdomen, and appendages. The carapace is bluish-green with a granular surface and a distinct "H"-shaped indentation in the center. The abdominal carapace is ivory-colored with a smooth surface and transverse indentations that divide it into petal-like sections. The anterior edge of the cephalothorax has serrated protrusions with sharp, needle-like tips, serving a defensive function. The abdomen is formed by the umbilicus, which is located close to the groove between the cephalothorax and abdominal carapace. Its edges are covered with fine hairs. Opening the umbilicus reveals the reproductive appendages, and the anus opens at the end of the umbilicus. The umbilicus is also an important characteristic for determining the sex of mud crabs; the female's umbilicus is oval, while the male's is a narrow, elongated triangular shape. The mud crab has many appendages. There are 5 pairs of head appendages, which are small in size and concentrated at the front of the cephalothorax, and are closely related to its feeding. There are 8 pairs of thoracic appendages. 3 pairs of maxillipeds are related to swallowing food, and the latter 5 pairs are thoracic legs. These 5 pairs of thoracic legs are further divided into: 1 pair of chelipeds, 3 pairs of walking legs, and 1 pair of swimming legs (when encountering danger or fighting for territory and mates, the mud crab will automatically cut off its chelipeds or walking legs to escape. After a period of time, it will regenerate the same type of thoracic legs and perform the same function as the original limbs). The appendages on the abdomen are different between males and females. Females have 4 pairs and males have 2 pairs, all of which are related to reproduction.

[0041] The mud crab is a eurythermal and euryhaline aquatic animal. Its optimal growth temperature is 14-32℃, with a lower limit of 7℃ and an upper limit of 37℃. If the water temperature exceeds the extreme temperature, the mud crab will stop feeding. Its optimal salinity range is 12.5‰-27.0‰, with extreme salinity not lower than 5‰ and not higher than 33‰; otherwise, the unfavorable osmotic pressure environment will prevent its survival. The mud crab requires a relatively high dissolved oxygen content, generally not lower than 3.5 mg / L. If the dissolved oxygen is below 1.0 mg / L, the mud crab will become sluggish due to hypoxia, stop feeding, and eventually die. The optimal pH range is between 7.8 and 8.5.

[0042] The growth and development of mud crabs can be divided into five stages: embryonic development, zoea larvae, megalopa larvae, juvenile crabs, and adult crabs. After embryonic development is complete, the zoea larvae break through the egg membrane and live a planktonic life, being omnivorous and feeding on small plants and animals in the water. After five molts, the zoea larvae develop into megalopa larvae, who begin to transition from a planktonic to a benthic lifestyle, changing their diet from primarily omnivorous to primarily carnivorous. The megalopa larvae then undergo another molt to become juvenile crabs, living entirely on the bottom and morphologically indistinguishable from adults. After six more growth molts, they become adults. Adult crabs then undergo a reproductive molt to become reproductively mature individuals. Males and females mate, lay eggs, and the eggs hatch into zoea larvae, completing one cycle of growth and development. The reproduction of mud crabs is closely related to environmental temperature. In Guangdong Province, the peak breeding season for mud crabs is from March to April and from June to September. In Fujian Province, it is from May to June and from August to September. In Guangxi Zhuang Autonomous Region, it is from March to October. In Taiwan Province, female mud crabs carrying eggs can be seen all year round.

[0043] The zoea larvae of the mud crab are omnivorous, transitioning to carnivorous behavior from the megalopa stage. Adult mud crabs are entirely carnivorous, preying on juvenile fish, small shrimp, shellfish (such as the red-fleshed blue clam), sandworms, and carcasses of dead animals. During molting, they need to consume large amounts of shellfish to accumulate energy and replenish nutrients. The mud crab burrows during the day and emerges at night to feed. With its sensitive sensory organs, it uses its chelipeds to grasp food and pass it to its third walking leg, which then passes it to its mandibles. The mandibles grind the food and send it into the digestive tract. Sometimes, it can be observed that the mud crab uses one cheliped to grasp food while the other cheliped tears it into smaller pieces before passing it to its third walking leg for further feeding.

[0044] Studies have shown that the mud crab (Scylla serrata) contains all eight essential amino acids required by the human body, and its unsaturated fatty acid content is higher than that of similar aquatic products such as the swimming crab (Swimmus trituberculatus). It is also rich in DHA and EPA. Its organic calcium is easily absorbed by the body. In particular, the mud crab, rich in the trace element selenium, is another excellent food supplement for human health benefits, including cancer prevention, anti-cancer, and anti-aging. Traditional Chinese medicine texts also record the mud crab in detail, noting its effects in relieving pain, promoting blood circulation, reducing swelling, and providing nourishment and strengthening. It is especially beneficial for postpartum women, treating conditions such as postpartum abdominal pain and insufficient breast milk, and also has therapeutic effects on pediatric hernias. Therefore, the mud crab is known as "sea ginseng."

[0045] In recent years, with the expansion of mud crab farming, the occurrence of mud crab diseases has become increasingly frequent, with mortality rates sometimes exceeding 60%, causing significant losses to the mud crab farming industry. Disease problems have become a key factor restricting the sustainable and healthy development of mud crab farming.

[0046] In the specific embodiments of this invention, Bifidobacterium longum, Lactobacillus reuteri, Bacillus licheniformis, Bacillus subtilis, and Saccharomyces cerevisiae were all purchased from the China Industrial Microbial Culture Collection Center.

[0047] Among them, the product number of Bifidobacterium longum is CICC 6197; the product number of Lactobacillus reuteri is CICC6128; the product number of Bacillus licheniformis is CICC 10108; the product number of Bacillus subtilis is CICC 24713; and the product number of Saccharomyces cerevisiae is CICC 1747.

[0048] In the specific embodiments of this invention, the *Bifidobacterium longum*, *Lactobacillus reuteri*, *Bacillus licheniformis*, *Bacillus subtilis*, and *Saccharomyces cerevisiae* cultures used were all obtained through activation culture followed by fermentation culture using liquid culture medium recommended by the China Industrial Microbial Culture Collection Center, with an effective viable count of 5.0 × 10⁻⁶. 8 ~5.0×10 9 cfu / mL.

[0049] The preparation method of chicory root powder used in the specific embodiments of the present invention is as follows: chicory root is washed, dried, and pulverized to obtain chicory root powder; the preparation method of oat flour is as follows: oats are dried and pulverized to obtain oat flour.

[0050] In the following examples, "parts" refers to "parts by weight".

[0051] Example 1

[0052] A method for preparing a compound feed to improve the disease resistance of mud crabs:

[0053] (1) The compound feed for improving the disease resistance of mud crabs is composed of the following raw materials in parts by weight: 30 parts soybean meal, 22 parts peanut meal, 20 parts fish meal, 6 parts compound microbial agent, 12 parts wheat flour, 5 parts chicory root powder, 6 parts oat flour, 2 parts corn cob enzymatic hydrolysate, 0.8 parts compound vitamins, 1.2 parts compound mineral salts and 3 parts traditional Chinese medicine composition.

[0054] The compound microbial agent consists of the following components in parts by weight: Bifidobacterium longum bacterial solution (effective viable count of 1.0 × 10⁻⁶). 9 Seven samples of *Lactobacillus reuteri* culture (cfu / mL) and seven samples of *Lactobacillus reuteri* culture (effective viable count 5.0 × 10⁻⁶). 8 Four samples of CFU / mL and Bacillus licheniformis bacterial suspension (effective viable count 2.0 × 10⁻⁶) were tested. 9 Four samples (cfu / mL).

[0055] This multivitamin consists of the following components in parts by weight: Vitamin A 12 parts, Vitamin B1 8 parts, Vitamin B6 20 parts, Vitamin C 40 parts, Vitamin D3 22 parts, Vitamin E 50 parts, and Folic Acid 10 parts.

[0056] The complex mineral salt is composed of the following components in parts by mass: 6 parts potassium dihydrogen phosphate, 12 parts ferric citrate, 6 parts manganese sulfate, 1 part magnesium sulfate heptahydrate, 0.4 parts copper sulfate pentahydrate, 0.3 parts zinc sulfate, and 12 parts potassium chloride.

[0057] (2) Preparation of traditional Chinese medicine composition:

[0058] Honeysuckle, isatis root, dandelion, and houttuynia cordata were dried and then pulverized to obtain honeysuckle powder, isatis root powder, dandelion powder, and houttuynia cordata powder.

[0059] Mix 3 parts honeysuckle powder, 6 parts isatis root powder, 6 parts dandelion powder, and 5 parts houttuynia cordata powder evenly to obtain a traditional Chinese medicine composition.

[0060] (3) Preparation of corn cob enzymatic hydrolysate:

[0061] Grind the corn cobs to 100 mesh to obtain corn cob powder;

[0062] Corn cob powder was added to water (the ratio of corn cob powder to water was 1g:15mL), cooked (at 100℃ for 1.5h), and then cooled (at 40℃). A compound enzyme was added (the amount of compound enzyme added was 0.6% of the mass of water), and enzymatic hydrolysis was carried out under ultrasonic treatment (ultrasonic power of 250W, temperature of 50℃, time of 30min). The enzyme was inactivated (at 90℃ for 30min), filtered, and the filtrate was concentrated and dried to obtain corn cob enzymatic hydrolysate.

[0063] The complex enzyme consists of xylanase (with an enzyme activity of 5000 U / g) and cellulase (with an enzyme activity of 10000 U / g) in a mass ratio of 3:1.

[0064] (4) Preparation of compound feed

[0065] Soybean meal, peanut meal, fish meal, wheat flour, chicory root powder, oat flour, corn cob hydrolysate, compound vitamins, compound mineral salts, and traditional Chinese medicine composition are mixed and pulverized to 200 mesh. Then, compound microbial agents are added, and after mixing evenly, a starch aqueous solution with a concentration of 0.2 wt.% is sprayed and granulated (particle size of 1 mm or 2.5 mm) to obtain a compound feed that improves the disease resistance of mud crabs.

[0066] Example 2

[0067] A method for preparing a compound feed to improve the disease resistance of mud crabs:

[0068] (1) The compound feed for improving the disease resistance of mud crabs is composed of the following raw materials in parts by weight: 25 parts soybean meal, 25 parts peanut meal, 20 parts fish meal, 4 parts compound microbial agent, 10 parts wheat flour, 6 parts chicory root powder, 4 parts oat flour, 1.5 parts corn cob hydrolysate, 1 part compound vitamin, 1.5 parts compound mineral salt and 4 parts traditional Chinese medicine composition.

[0069] The compound microbial agent consists of the following components in parts by weight: Bifidobacterium longum bacterial solution (effective viable count of 1.0 × 10⁻⁶). 9 Six samples of *Lactobacillus reuteri* culture (cfu / mL) and six samples of *Lactobacillus reuteri* culture (effective viable count 5.0 × 10⁻⁶). 8 Six samples of CFU / mL and Bacillus licheniformis bacterial suspension (effective viable count 2.0 × 10⁻⁶) were tested. 9 Two portions (cfu / mL).

[0070] This multivitamin consists of the following components in parts by weight: Vitamin A 10 parts, Vitamin B1 5 parts, Vitamin B6 25 parts, Vitamin C 45 parts, Vitamin D3 25 parts, Vitamin E 40 parts, and Folic Acid 12 parts.

[0071] The complex mineral salt is composed of the following components in parts by mass: 8 parts potassium dihydrogen phosphate, 10 parts ferric citrate, 5 parts manganese sulfate, 1 part magnesium sulfate heptahydrate, 0.5 parts copper sulfate pentahydrate, 0.6 parts zinc sulfate, and 10 parts potassium chloride.

[0072] (2) Preparation of traditional Chinese medicine composition:

[0073] Honeysuckle, isatis root, dandelion, and houttuynia cordata were dried and then pulverized to obtain honeysuckle powder, isatis root powder, dandelion powder, and houttuynia cordata powder.

[0074] Mix 2 parts honeysuckle powder, 5 parts isatis root powder, 8 parts dandelion powder and 4 parts houttuynia cordata powder evenly to obtain a traditional Chinese medicine composition.

[0075] (3) Preparation of corn cob enzymatic hydrolysate:

[0076] Grind the corn cobs to 100 mesh to obtain corn cob powder;

[0077] Corn cob powder was added to water (the ratio of corn cob powder to water was 1g:12mL), cooked (at 95℃ for 1.5h), and then cooled (at 40℃). A compound enzyme was added (the amount of compound enzyme added was 0.5% of the mass of water), and enzymatic hydrolysis was carried out under ultrasonic treatment (ultrasonic power of 300W, temperature of 45℃, time of 20min). The enzyme was inactivated (at 90℃ for 30min), and then filtered. The filtrate was concentrated and dried to obtain the corn cob enzymatic hydrolysate.

[0078] The complex enzyme consists of xylanase (with an enzyme activity of 5000 U / g) and cellulase (with an enzyme activity of 10000 U / g) in a mass ratio of 4:1.

[0079] (4) Preparation of compound feed

[0080] Soybean meal, peanut meal, fish meal, wheat flour, chicory root powder, oat flour, corn cob hydrolysate, compound vitamins, compound mineral salts, and traditional Chinese medicine composition are mixed and pulverized to 200 mesh. Then, compound microbial agents are added, and after mixing evenly, a starch aqueous solution with a concentration of 0.2 wt.% is sprayed and granulated (particle size of 1 mm or 2.5 mm) to obtain a compound feed that improves the disease resistance of mud crabs.

[0081] Example 3

[0082] A method for preparing a compound feed to improve the disease resistance of mud crabs:

[0083] (1) The compound feed for improving the disease resistance of mud crabs is composed of the following raw materials in parts by weight: 35 parts soybean meal, 15 parts peanut meal, 15 parts fish meal, 5 parts compound microbial agent, 10 parts wheat flour, 4 parts chicory root powder, 6 parts oat flour, 2.5 parts corn cob hydrolysate, 0.5 parts compound vitamins, 1 part compound mineral salt and 2 parts traditional Chinese medicine composition.

[0084] The compound microbial agent consists of the following components in parts by weight: Bifidobacterium longum bacterial solution (effective viable count of 1.0 × 10⁻⁶). 9 Eight samples of *Lactobacillus reuteri* culture (cfu / mL) and 5.0 × 10⁻⁶ effective viable bacteria. 8 Five samples of CFU / mL and Bacillus licheniformis bacterial suspension (effective viable count 2.0 × 10⁻⁶) were tested. 9 Two portions (cfu / mL).

[0085] This multivitamin consists of the following components in parts by weight: 15 parts vitamin A, 6 parts vitamin B1, 20 parts vitamin B6, 50 parts vitamin C, 20 parts vitamin D3, 40 parts vitamin E, and 15 parts folic acid.

[0086] The complex mineral salt is composed of the following components in parts by mass: 5 parts potassium dihydrogen phosphate, 12 parts ferric citrate, 4 parts manganese sulfate, 2 parts magnesium sulfate heptahydrate, 0.2 parts copper sulfate pentahydrate, 0.6 parts zinc sulfate, and 12 parts potassium chloride.

[0087] (2) Preparation of traditional Chinese medicine composition:

[0088] Honeysuckle, isatis root, dandelion, and houttuynia cordata were dried and then pulverized to obtain honeysuckle powder, isatis root powder, dandelion powder, and houttuynia cordata powder.

[0089] Mix 2.5 parts of honeysuckle powder, 4 parts of isatis root powder, 5 parts of dandelion powder and 6 parts of houttuynia cordata powder evenly to obtain a traditional Chinese medicine composition.

[0090] (3) Preparation of corn cob enzymatic hydrolysate:

[0091] Grind the corn cobs to 100 mesh to obtain corn cob powder;

[0092] Corn cob powder was added to water (the ratio of corn cob powder to water was 1g:15mL), cooked (at 105℃ for 1 hour), and then cooled (at 40℃). A compound enzyme was added (the amount of compound enzyme added was 0.7% of the mass of water), and enzymatic hydrolysis was carried out under ultrasonic treatment (ultrasonic power of 250W, temperature of 45℃, time of 40 minutes). The enzyme was inactivated (at 90℃ for 30 minutes), and then filtered. The filtrate was concentrated and dried to obtain the corn cob enzymatic hydrolysate.

[0093] The complex enzyme consists of xylanase (with an enzyme activity of 5000 U / g) and cellulase (with an enzyme activity of 10000 U / g) in a mass ratio of 2:1.

[0094] (4) Preparation of compound feed

[0095] Soybean meal, peanut meal, fish meal, wheat flour, chicory root powder, oat flour, corn cob hydrolysate, compound vitamins, compound mineral salts, and traditional Chinese medicine composition are mixed and pulverized to 200 mesh. Then, compound microbial agents are added, and after mixing evenly, a starch aqueous solution with a concentration of 0.2 wt.% is sprayed and granulated (particle size of 1 mm or 2.5 mm) to obtain a compound feed that improves the disease resistance of mud crabs.

[0096] Comparative Example 1

[0097] Same as Example 1, except that the compound feed for improving the disease resistance of mud crabs does not contain compound microbial agents.

[0098] Comparative Example 2

[0099] Same as Example 1, except that the compound feed for improving the disease resistance of mud crabs does not contain the traditional Chinese medicine composition.

[0100] Comparative Example 3

[0101] Same as Example 1, except that the compound feed for improving the disease resistance of mud crabs does not contain chicory root powder, oat flour and corn cob hydrolysate.

[0102] Comparative Example 4

[0103] Same as Example 1, except that honeysuckle in the herbal composition is replaced with an equal amount of Atractylodes lancea, and Isatis indigotica is replaced with an equal amount of Isatis tinctoria.

[0104] Preparation of traditional Chinese medicine composition: Atractylodes lancea, Isatis indigotica, dandelion and houttuynia cordata were dried and pulverized to obtain Atractylodes lancea powder, Isatis indigotica powder, dandelion powder and houttuynia cordata powder.

[0105] Mix 3 parts of Atractylodes lancea powder, 6 parts of Isatis indigotica powder, 6 parts of Taraxacum mongolicum powder, and 5 parts of Houttuynia cordata powder evenly to obtain a traditional Chinese medicine composition.

[0106] Comparative Example 5

[0107] Same as Example 1, except that the Bifidobacterium longum bacterial solution in the compound microbial agent is replaced with an equal mass fraction of Bacillus subtilis bacterial solution (effective viable count of 5.0 × 10⁻⁶). 8 The *Lactobacillus reuteri* culture was replaced with an equal amount of *Saccharomyces cerevisiae* culture (effective viable count 5.0 × 10⁻⁶ CFU / mL). 8 (cfu / mL).

[0108] Example 1

[0109] In a certain agricultural breeding base, 24 experimental plots were demarcated using polyethylene mesh, each plot having an area of ​​100m². 2 Water supply and drainage systems were set up. Healthy, vigorous, uniformly sized, and disease-free adult mud crabs were selected and released into each experimental plot. In spring, 150 adult mud crabs (average weight 20g) were released into each plot. The 24 experimental plots were divided into 8 groups, and each group was fed with the compound feed (particle size 2.5mm) prepared in Examples 1-3 and Comparative Examples 1-5, respectively. After two months of rearing, the crabs were harvested collectively. The number and average weight of mud crabs in each experimental plot were counted, and the actual effects of the compound feed in each group were compared (no antibiotics were used during the rearing period). The statistical results are shown in Table 1.

[0110] Table 1. Breeding effects of compound feed

[0111]

[0112] The activity of phenol oxidase (PO) in mud crabs was measured one month after feeding them. The measurement method is as follows:

[0113] Take 3.4 mL of 0.1 M pH 7.0 phosphate buffer, add 200 μL of serum to be tested (wipe the base of the crab's walking legs with an alcohol swab, and use a 5 mL disposable syringe to aspirate hemolymph from the junction of the fourth walking leg and the dorsal side of the crab. Centrifuge at 8000 r / min for 5 min at 4℃, then aspirate the supernatant light blue serum and store at -20℃ for later use). Incubate at 37℃ for 15 min, add 400 μL of 6 mg / mL L-DOPA, and incubate at 25℃. Read the optical density (OD) value at 490 nm every 5 min, and measure for 30 min. The enzyme activity unit (U) is defined as an increase of 0.001 OD per minute.

[0114] Table 2. Phenol oxidase (PO) activity

[0115]

[0116] As can be seen from Table 2, feeding the compound feed of the present invention can increase the activity of phenol oxidase (PO) in mud crabs and improve their disease resistance.

[0117] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A compound feed for improving the disease resistance of blue crabs, characterized in that, The raw materials include the following mass fractions: soybean meal 25-35 parts, peanut meal 15-25 parts, fish meal 15-20 parts, compound microbial agent 4-6 parts, wheat flour 10-12 parts, chicory root powder 4-6 parts, oat flour 4-6 parts, corncob enzymolysis product 1.5-2.5 parts, compound vitamin 0.5-1 part, compound mineral salt 1-1.5 parts and traditional Chinese medicine composition 2-4 parts. ​ 2. The composite feed according to claim 1, characterized in that, The compound microbial agent includes the following mass fractions of components: Bifidobacterium longum 6-8 parts, Lactobacillus reuteri 4-6 parts and Bacillus licheniformis 2-4 parts.

3. The composite feed according to claim 1, characterized in that, The preparation method of the corncob enzymolysis product includes the following steps: The corncob is ground to obtain corncob powder; The corncob powder is added into water, and after cooking and cooling, a compound enzyme is added for enzymolysis, and after enzyme inactivation, the filtrate is obtained by filtration, concentrated and dried to obtain the corncob enzymolysis product.

4. The composite feed according to claim 3, characterized in that, The use amount ratio of the corncob powder to water is 1g: 12-15mL; And / or, the cooking temperature is 95-105℃, and the time is 1-1.5h.

5. The composite feed according to claim 3, characterized in that, The compound enzyme includes xylanase and cellulase in a mass ratio of (2-4):1; And / or, the addition amount of the compound enzyme is 0.5-0.7% of the mass of water; And / or, the enzymolysis conditions include: ultrasonic power 250-300W, temperature 45-50℃, and time 20-40min.

6. The composite feed according to claim 1, characterized in that, The compound vitamin includes the following mass fractions of components: vitamin A 10-15 parts, vitamin B1 5-8 parts, vitamin B6 20-25 parts, vitamin C 40-50 parts, vitamin D3 20-25 parts, vitamin E 40-50 parts and folic acid 10-15 parts.

7. The composite feed according to claim 1, characterized in that, The compound mineral salt includes the following mass fractions of components: potassium dihydrogen phosphate 5-8 parts, ferric citrate 10-12 parts, manganese sulfate 4-6 parts, magnesium sulfate heptahydrate 1-2 parts, copper sulfate pentahydrate 0.2-0.5 parts, zinc sulfate 0.3-0.6 parts and potassium chloride 10-12 parts.

8. The composite feed according to claim 1, characterized in that, The traditional Chinese medicine composition includes the following mass fractions of raw materials: honeysuckle 2-3 parts, isatis root 4-6 parts, dandelion 5-8 parts and fishy grass 4-6 parts.

9. A method for preparing the compound feed for improving the disease resistance of blue crab according to any one of claims 1-8, characterized in that, The method includes the following steps: The raw materials of the compound feed for improving the disease resistance of juvenile crabs are uniformly mixed and granulated to obtain the compound feed for improving the disease resistance of juvenile crabs.

10. The method of claim 9, wherein, When the compound feed is used for juvenile crabs, the particle size of the granulation is 0.5-1.5mm; When the compound feed is used for adult crabs, the particle size of the granulation is 1.5-3.5mm.

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