Antibiotic-free feed additive for breeding crucian carps and preparation method of antibiotic-free feed additive

Abstract

The invention relates to an antibiotic-free feed additive for breeding crucian carps and a preparation method of the antibiotic-free feed additive, and belongs to the technical field of feed additives. According to the feed additive, seaweeds and Chinese herbal medicines are used as raw materials and are subjected to staged fermentation with compound probiotics, a phagostimulant is added, and freeze drying is performed to prepare the antibiotic-free crucian breeding feed additive, so that the prevalence rate of crucian can be reduced, the survival rate can be increased, and the growth of crucian can be accelerated; the problem of drug resistance caused by antibiotic abuse in crucian breeding in the prior art can be solved, and unification of high antibacterial activity, biological safety and environmental friendliness in crucian breeding is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of feed additives and relates to an antibiotic-free feed additive for cultured crucian carp and a preparation method thereof. Background Art

[0002] Crucian carp farming faces many challenges, among which bacterial infection is one of the most common and serious problems. Bacterial infection not only leads to slow growth and increased morbidity of crucian carp, but can also cause large-scale fish deaths, resulting in huge economic losses for farmers. Common pathogenic bacteria such as Aeromonas hydrophila and Vibrio can multiply rapidly in water bodies and spread through water flow, feed, and other channels, seriously affecting the stability of the farming environment and the health of crucian carp. In addition, due to the high farming density and rapid environmental changes, the immunity of crucian carp is often insufficient to resist the invasion of these pathogenic microorganisms, further exacerbating the risk of bacterial infection.

[0003] To combat bacterial infections, many fish farmers use antibiotics for both prevention and treatment. However, the overuse of antibiotics has become increasingly problematic, leading to numerous negative consequences. Excessive or inappropriate use of antibiotics not only leads to excessive antibiotic residues in aquatic products, endangering consumer health, but also fosters bacterial resistance, rendering previously effective antibiotics ineffective. Furthermore, long-term antibiotic use can disrupt the ecological balance of water bodies, impacting the survival and development of other aquatic life. Therefore, reducing or even eliminating antibiotic use has become a pressing issue for the crucian carp aquaculture industry.

[0004] To address these challenges, this project proposed an innovative antibiotic-free crucian carp feed additive with significant advantages. First, the additive uses seaweed and Chinese herbal medicine as its main raw materials, combined with the fermentation technology of compound probiotics, which can effectively enhance the immunity and disease resistance of crucian carp and reduce the occurrence of bacterial infections. Second, the attractant used in the additive improves the palatability of the feed, promotes the feeding and growth of crucian carp, and improves the breeding efficiency. Moreover, this feed additive conforms to the concept of green farming, not only avoiding the problem of antibiotic residues, but also maintaining the ecological balance of the water body, providing a practical path for sustainable aquaculture. Summary of the Invention

[0005] The present invention relates to a feed additive for antibiotic-free aquaculture crucian carp and a preparation method thereof, belonging to the technical field of feed additives. The feed additive is prepared from seaweed and Chinese herbal medicines, fermented in stages with composite probiotics, added with an attractant, and then freeze-dried to produce an antibiotic-free feed additive for aquaculture crucian carp. The feed additive can reduce the incidence of disease in aquaculture crucian carp, increase its survival rate, and accelerate its growth. It can solve the problem of drug resistance caused by the abuse of antibiotics in aquaculture crucian carp using traditional techniques, and achieve a combination of high antimicrobial activity, biosafety, and environmental friendliness in aquaculture crucian carp.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A feed additive for antibiotic-free cultured crucian carp comprises the following raw materials in parts by weight: 20-30 parts by weight of seaweed, 15-25 parts by weight of Chinese herbal medicine, 0.1-0.2 parts by weight of compound probiotics and 5-10 parts by weight of an attractant.

[0008] As a preferred technical solution of the present invention, the Chinese herbal medicine includes licorice, astragalus, honeysuckle, cornus officinalis and perilla leaves, and the mass ratio of the licorice, astragalus, honeysuckle, cornus officinalis and perilla leaves is 4-5:5-6:3-4:2-3:2-3.

[0009] As a preferred technical solution of the present invention, the composite probiotics include Saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis, Bifidobacterium longum and Bifidobacterium breve, and the mass ratio of Saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis, Bifidobacterium longum and Bifidobacterium breve is 3-4:2-3:2-3:2-3:1-2:1-3.

[0010] As a preferred technical solution of the present invention, the attractant is at least one of fish meal, fish bone meal, allicin, and saccharin calcium.

[0011] Furthermore, the method for preparing the antibiotic-free feed additive for cultured crucian carp comprises the following steps:

[0012] (1) Clean the seaweed and Chinese herbal medicines, put them into a grinder and grind them for 2-3 minutes to obtain seaweed powder and Chinese herbal medicine powder;

[0013] (2) mixing glucose solution, seaweed powder and Chinese herbal medicine powder uniformly and adding them into a fermentation tank, wherein the mass ratio of the glucose solution to the seaweed powder and the Chinese herbal medicine is 10-50:4-6:3-5;

[0014] (3) inoculating Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum, and Bifidobacterium breve and fermenting for 12-24 hours until the pH value drops to 4.0-4.5;

[0015] (4) inoculating Saccharomyces cerevisiae, Bacillus pumilus, or Bacillus subtilis and fermenting for 24-48 hours to obtain a fermentation liquid;

[0016] (5) filtering the fermentation liquid with a 400-mesh filter, adding an attractant and mixing evenly, and freeze-drying to obtain an antibiotic-free feed additive for cultured crucian carp.

[0017] As a preferred technical solution of the present invention, the glucose solution in step (2) is prepared by dissolving 1-5 parts by weight of glucose in 100 parts by weight of deionized water, sterilizing it in an autoclave at 121° C. for 10-20 minutes, and then cooling it for use.

[0018] As a preferred technical solution of the present invention, the inoculation in step (3) is carried out in an anaerobic environment, with the temperature controlled at 37-40° C. and the pH at 6.0-6.5.

[0019] As a preferred technical solution of the present invention, the initial OD value of the inoculation in step (4) is 0.05-0.2, and during the logarithmic growth phase, the OD is controlled at 1.0-2.0, and the fermentation temperature is 30-35°C.

[0020] As a preferred technical solution of the present invention, the freeze-drying in step (5) refers to pre-freezing at -80 to -40°C until completely frozen, then placing it in a freeze dryer, sublimating at -40 to -20°C and a low pressure of 10mTorr-100mTorr for 5-15 hours, raising the temperature to 20-30°C, and maintaining the low pressure for 5-15 hours until the sample is dry.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention significantly improves the immunity and disease resistance of crucian carp by using a fermentation technology that combines seaweed and Chinese herbal medicine with compound probiotics. Seaweed and Chinese herbal medicine are rich in vitamins, minerals, and bioactive substances that can enhance the immune system of crucian carp and resist common bacterial infections. In addition, the compound probiotics regulate the intestinal microbial community of crucian carp, promote digestion and absorption, and enhance the immune response, thereby further reducing the incidence of disease and ensuring the healthy growth of the fish.

[0023] (2) The attractant contained in the feed additive of the present invention improves the palatability of the feed and significantly promotes the feeding behavior of crucian carp, thereby increasing the amount of food eaten by crucian carp, allowing them to take in sufficient nutrients, promoting their growth and development, and improving aquaculture yield and economic benefits.

[0024] (3) This invention adheres to the concept of green aquaculture, completely avoiding the use of antibiotics and fundamentally solving the problem of antibiotic residues. By combining Chinese herbal medicine and probiotics, it provides a safe and environmentally friendly alternative, maintains the stability of the water ecological environment, promotes the development of sustainable aquaculture, and meets the current social needs of environmental protection and health. DETAILED DESCRIPTION

[0025] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0026] In the following examples and comparative examples, the Aeromonas hydrophila DLNG101 was purchased from the Institute of Hydrobiology, Chinese Academy of Sciences; Saccharomyces cerevisiae, Bacillus pumilus and Bacillus subtilis were purchased from Wanjia Reference Material Research and Development Center; Lactobacillus delbrueckii subsp. lactis and Bifidobacterium breve were purchased from Mingzhou Biotechnology Co., Ltd.; and Bifidobacterium longum was purchased from Zhongke Jiayi Bioengineering Co., Ltd.

[0027] Example 1

[0028] A feed additive for antibiotic-free cultured crucian carp comprises the following raw materials in parts by weight: 25 parts by weight of seaweed, 20 parts by weight of Chinese herbal medicine, 0.15 parts by weight of compound probiotics and 8 parts by weight of an attractant.

[0029] The Chinese herbal medicines include liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaves, and the mass ratio of the liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaves is 5:6:3:3:3.

[0030] The composite probiotics include saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis, Bifidobacterium longum and Bifidobacterium breve, and the mass ratio of the saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis, Bifidobacterium longum and Bifidobacterium breve is 4:3:3:2:2:2.

[0031] The attractant is prepared by mixing 1 part by weight of fish meal, 1 part by weight of allicin and 1 part by weight of saccharin calcium.

[0032] The method for preparing the antibiotic-free feed additive for cultured crucian carp comprises the following steps:

[0033] (1) Clean the seaweed and Chinese herbal medicines, put them into a grinder and grind them for 3 minutes to obtain seaweed powder and Chinese herbal medicine powder;

[0034] (2) Mixing glucose solution, seaweed powder and Chinese herbal medicine powder evenly and adding them into a fermentation tank, wherein the mass ratio of glucose solution to seaweed powder and Chinese herbal medicine is 30:5:4;

[0035] (3) inoculating Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum, and Bifidobacterium breve and fermenting for 18 hours until the pH value dropped to 4.2;

[0036] (4) inoculating Saccharomyces cerevisiae, Bacillus pumilus, and Bacillus subtilis and fermenting for 36 hours to obtain a fermentation liquid;

[0037] (5) filtering the fermentation liquid with a 400-mesh filter, adding an attractant and mixing evenly, and freeze-drying to obtain an antibiotic-free feed additive for cultured crucian carp.

[0038] The glucose solution in step (2) is prepared by dissolving 2 parts by weight of glucose in 100 parts by weight of deionized water, sterilizing the solution at 121° C. in an autoclave for 15 minutes, and then cooling the solution for later use.

[0039] The inoculation in step (3) is carried out in an anaerobic environment, with the temperature controlled at 38° C. and the pH at 6.0.

[0040] The initial OD value of the inoculation in step (4) is 0.1. During the logarithmic growth phase, the OD is controlled at 1.5, and the fermentation temperature is 32°C.

[0041] The freeze drying in step (5) refers to pre-freezing at -80°C until completely frozen, then placing it in a freeze dryer, sublimating it at -40°C and 60mTorr low pressure for 10 hours, raising the temperature to 20°C, and maintaining the low pressure for 10 hours until the sample is dry.

[0042] Example 2

[0043] A feed additive for antibiotic-free cultured crucian carp comprises the following raw materials in parts by weight: 20 parts by weight of seaweed, 16 parts by weight of Chinese herbal medicine, 0.1 parts by weight of compound probiotics and 5 parts by weight of an attractant.

[0044] The Chinese herbal medicines include liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaves, and the mass ratio of the liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaves is 4:5:3:2:2.

[0045] The composite probiotics include saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis, Bifidobacterium longum and Bifidobacterium breve, and the mass ratio of the saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis, Bifidobacterium longum and Bifidobacterium breve is 3:2:2:2:2:2.

[0046] The attractant is prepared by mixing 1 weight part of fish bone powder with 1 weight part of allicin.

[0047] The method for preparing the antibiotic-free feed additive for cultured crucian carp comprises the following steps:

[0048] (1) Clean the seaweed and Chinese herbal medicines, put them into a grinder and grind them for 2 minutes to obtain seaweed powder and Chinese herbal medicine powder;

[0049] (2) Mixing glucose solution, seaweed powder and Chinese herbal medicine powder evenly and adding them into a fermentation tank, wherein the mass ratio of glucose solution to seaweed powder and Chinese herbal medicine is 20:5:4;

[0050] (3) inoculating Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum, and Bifidobacterium breve and fermenting for 12 hours until the pH value dropped to 4.5;

[0051] (4) inoculating Saccharomyces cerevisiae, Bacillus pumilus, and Bacillus subtilis and fermenting for 24 hours to obtain a fermentation liquid;

[0052] (5) filtering the fermentation liquid with a 400-mesh filter, adding an attractant and mixing evenly, and freeze-drying to obtain an antibiotic-free feed additive for cultured crucian carp.

[0053] The glucose solution in step (2) is prepared by dissolving 3 parts by weight of glucose in 100 parts by weight of deionized water, sterilizing the solution at 121° C. in an autoclave for 15 minutes, and then cooling the solution for later use.

[0054] The inoculation in step (3) is carried out in an anaerobic environment, with the temperature controlled at 38° C. and the pH at 6.0.

[0055] The initial OD value of the inoculation in step (4) is 0.1. During the logarithmic growth phase, the OD is controlled at 1.5, and the fermentation temperature is 30°C.

[0056] The freeze drying in step (5) refers to pre-freezing at -80°C until completely frozen, then placing it in a freeze dryer, sublimating at -40°C and 50mTorr low pressure for 8 hours, raising the temperature to 30°C, and maintaining the low pressure for 8 hours until the sample is dry.

[0057] Comparative Example 1

[0058] On the basis of Example 1, no seaweed was added, the amount of Chinese herbal medicine added was 45 parts by weight, and the rest remained the same as in Example 1.

[0059] Comparative Example 2

[0060] On the basis of Example 1, no Chinese medicinal herbs were added, the amount of seaweed added was 45 parts by weight, and the rest remained the same as in Example 1.

[0061] Comparative Example 3

[0062] On the basis of Example 1, no composite probiotics were added, no fermentation treatment was performed, and the rest were consistent with Example 1.

[0063] Comparative Example 4

[0064] On the basis of Example 1, no fermentation treatment was performed, and the rest was the same as in Example 1.

[0065] Comparative Example 5

[0066] On the basis of Example 1, licorice was not added, and the mass ratio of astragalus, honeysuckle, cornus officinalis and perilla leaves was 11:3:3:3. The rest was consistent with Example 1.

[0067] Comparative Example 6

[0068] On the basis of Example 1, astragalus was not added, and the mass ratio of liquorice, honeysuckle, cornus officinalis and perilla leaf was 5:9:3:3, and the rest of Example 1 remained the same.

[0069] Comparative Example 7

[0070] On the basis of Example 1, honeysuckle was not added, and the mass ratio of liquorice, astragalus, cornus officinalis and perilla leaves was 5:6:6:3, and the rest was consistent with the example.

[0071] Comparative Example 8

[0072] On the basis of Example 1, Cornus officinalis was not added, and the mass ratio of Licorice, Astragalus, Honeysuckle and Perilla Leaf was 5:6:3:6, and the rest was consistent with Example 1.

[0073] Comparative Example 9

[0074] On the basis of Example 1, no perilla leaf was added, and the mass ratio of liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaf was 8:6:3:3, and the rest was consistent with Example 1.

[0075] Comparative Example 10

[0076] On the basis of Example 1, without adding Saccharomyces cerevisiae, the mass ratio of Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum and Bifidobacterium breve was 7:3:2:2:2, and the rest was consistent with Example 1.

[0077] Comparative Example 11

[0078] On the basis of Example 1, Bacillus pumilus was not added, and the mass ratio of Saccharomyces cerevisiae, Bacillus subtilis, Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum and Bifidobacterium breve was 4:6:2:2:2, and the rest was consistent with Example 1.

[0079] Comparative Example 12

[0080] On the basis of Example 1, Bacillus subtilis was not added, and the mass ratio of Saccharomyces cerevisiae, Bacillus pumilus, Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum and Bifidobacterium breve was 7:3:2:2:2, and the rest was consistent with Example 1.

[0081] Comparative Example 13

[0082] On the basis of Example 1, Lactobacillus delbrueckii subsp. lactis was not added, the mass ratio of Saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Bifidobacterium longum and Bifidobacterium breve was 4:3:3:4:2, and the rest was consistent with Example 1.

[0083] Comparative Example 14

[0084] On the basis of Example 1, Bifidobacterium longum was not added, and the mass ratio of Saccharomyces cerevisiae, Bacillus brevis, Bacillus subtilis, Lactobacillus delbrueckii subsp. lactis and Bifidobacterium breve was 4:3:3:2:4, and the rest was consistent with Example 1.

[0085] Comparative Example 15

[0086] On the basis of Example 1, Bifidobacterium breve was not added, and the mass ratio of Saccharomyces cerevisiae, Bacillus breve, Bacillus subtilis, Lactobacillus delbrueckii subsp. lactis and Bifidobacterium longum was 4:3:3:4:2, and the rest was consistent with Example 1.

[0087] Comparative Example 16

[0088] On the basis of Example 1, no attractant was added, and the rest was consistent with Example 1.

[0089] This experiment adopts a single-factor factorial experimental design. The specific steps are as follows:

[0090] First, several juvenile crucian carp were pre-fed at 22°C, pH 8, and OD greater than 5 mg / L for 15 days to adapt them to the culture environment. They were fed with basic feed at 9:00 and 17:00 every day, with a feeding rate of 2%.

[0091] Aeromonas hydrophila DLNG101 was washed with 1% saline and accurately mixed with a spectrophotometer to a final concentration of 1.0×10 6 CFU / mL, 2000 crucian carp were randomly selected and injected with 100 μL / tail of Aeromonas hydrophila for the toxicity test.

[0092] The crucian carp in the challenge experiment were randomly divided into 20 groups, with 100 crucian carp in each group, of which 1 group was used as a blank control group; 1 group was used as a positive control group; and 18 groups were used as experimental groups, including Examples 1-2 and Comparative Examples 1-16;

[0093] Ten crucian carps were randomly selected from each group and weighed, which was recorded as the initial mass (g);

[0094] A 40-day feeding experiment was conducted. During the feeding experiment, the water temperature was maintained at 22°C, the pH value was 8, and the dissolved oxygen was >5 mg / L. The fish were fed at 9:00 and 17:00 daily, with a feeding rate of 2%. The blank control group was fed a basic feed, the experimental group was fed a basic feed supplemented with 5% of the additives prepared in the examples and comparative examples, and the positive control group was fed an antibiotic basic feed supplemented with 20 mg of oxytetracycline per kilogram of fish body weight per day and the water was maintained at 0.5 mg / L of copper sulfate.

[0095] The number of surviving crucian carps was recorded, and 10 crucian carps were randomly selected and weighed, which was recorded as the mass at the end of the experiment (g).

[0096] Survival rate = number of surviving tails / initial tails × 100%

[0097] Weight gain rate = (weight at the end of the experiment - initial weight) / initial weight × 100%

[0098] The growth results of crucian carp are as follows

[0099]

[0100]

[0101] As can be seen from the test results in the table, the present invention significantly improves the survival rate of crucian carp by using seaweed and Chinese herbal medicine combined with the fermentation technology of compound probiotics, and the effect is comparable to the use of antibiotics. Seaweed is rich in vitamins and minerals, and licorice, astragalus honeysuckle, cornus officinalis and perilla leaves are rich in bioactive substances, which synergistically help resist common bacterial infections. Saccharomyces cerevisiae, Bacillus pumilus, Bacillus subtilis, Lactobacillus delbrueckii lactis subsp. lactis, Bifidobacterium longum and Bifidobacterium breve work together to regulate the intestinal microbial community of crucian carp, promote digestion and absorption and enhance immune response. The attractant improves the palatability of the feed, increases the amount of food eaten by crucian carp, and promotes the growth and development of crucian carp.

[0102] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any indirect modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A feed additive for antibiotic-free cultured crucian carp, characterized in that: The raw materials include the following parts by weight: 20-30 parts by weight of seaweed, 15-25 parts by weight of Chinese herbal medicine, 0.1-0.2 parts by weight of compound probiotics and 5-10 parts by weight of food attractant.

2. The feed additive for antibiotic-free cultured crucian carp according to claim 1, characterized in that: The Chinese herbal medicines include liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaves, and the mass ratio of the liquorice, astragalus, honeysuckle, cornus officinalis and perilla leaves is 4-5:5-6:3-4:2-3:2-3.

3. The feed additive for antibiotic-free cultured crucian carp according to claim 1, characterized in that: The composite probiotics include saccharomyces cerevisiae, bacillus pumilus, bacillus subtilis, lactobacillus delbrueckii lactic acid subspecies, bifidobacterium longum and bifidobacterium breve, and the mass ratio of the saccharomyces cerevisiae, bacillus pumilus, bacillus subtilis, lactobacillus delbrueckii lactic acid subspecies, bifidobacterium longum and bifidobacterium breve is 3-4:2-3:2-3:2-3:1-2:1-3.

4. The feed additive for antibiotic-free cultured crucian carp according to claim 1, characterized in that: The attractant is at least one of fish meal, fish bone meal, allicin and saccharin calcium.

5. A method for preparing the antibiotic-free feed additive for cultured crucian carp according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Clean the seaweed and Chinese herbal medicine, put them into a grinder and grind them for 2-3 minutes to obtain seaweed powder and Chinese herbal medicine powder; (2) mixing the glucose solution, seaweed powder and Chinese herbal medicine powder uniformly and adding the mixture into a fermentation tank, wherein the mass ratio of the glucose solution to the seaweed powder and the Chinese herbal medicine is 10-50:4-6:3-5; (3) inoculating Lactobacillus delbrueckii subsp. lactis, Bifidobacterium longum, and Bifidobacterium breve and fermenting for 12-24 hours until the pH value drops to 4.0-4.5; (4) inoculating Saccharomyces cerevisiae, Bacillus pumilus, or Bacillus subtilis and fermenting for 24-48 hours to obtain a fermentation liquid; (5) filtering the fermented liquid with a 400-mesh filter, adding an attractant and mixing evenly, and freeze-drying to obtain an antibiotic-free feed additive for cultured crucian carp.

6. The method for preparing a feed additive for antibiotic-free cultured crucian carp according to claim 5, characterized in that: The glucose solution in step (2) is prepared by dissolving 1-5 parts by weight of glucose in 100 parts by weight of deionized water, sterilizing the solution at 121° C. in an autoclave for 10-20 minutes, and then cooling the solution for later use.

7. The method for preparing a feed additive for antibiotic-free cultured crucian carp according to claim 5, characterized in that: The inoculation in step (3) is carried out in an anaerobic environment, with the temperature controlled at 37-40° C. and the pH at 6.0-6.

5.

8. The method for preparing a feed additive for antibiotic-free cultured crucian carp according to claim 5, characterized in that: The initial OD value of the inoculation in step (4) is 0.05-0.

2. During the logarithmic growth phase, the OD is controlled at 1.0-2.0, and the fermentation temperature is 30-35°C.

9. The method for preparing a feed additive for antibiotic-free cultured crucian carp according to claim 5, characterized in that: The freeze drying in step (5) refers to pre-freezing at -80 to -40°C until completely frozen, then placing in a freeze dryer, sublimating at -40 to -20°C, 10mTorr-100mTorr low pressure for 5-15 hours, raising the temperature to 20-30°C, and maintaining the low pressure for 5-15 hours until the sample is dry.

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