Compound feed for improving immunity of geese and preparation method of compound feed

Abstract

The invention discloses a compound feed for improving the immunity of geese and a preparation method, belongs to the field of livestock feeds, and solves the technical problems that the existing goose feed is difficult to intercept and remove macromolecular anti-nutritional factors, so that the intestinal tracts of the geese cannot absorb effective nutrient substances, and the immunity is low. The compound feed comprises basic nutrient components such as wheat flour, corn oil, rice bran, distillers' grains, apple peel, vinegar residues and soybean meal, as well as modified chitosan, modified glucan and probiotics. The modified chitosan and the modified dextran form a reticular structure compound with the pore diameter of 10-20 nm in the small intestine of the goose, macromolecular anti-nutritional factors can be intercepted, micromolecular nutrition can be allowed to pass through, and the modified chitosan and the modified dextran are discharged along with the anti-nutritional factors after being degraded in the large intestine; the probiotics are used for assisting digestion. During preparation, the processes of layered mixing, low-temperature granulation and drying and twice sieving are adopted. The goose feed is balanced in nutrition and controllable in cost, anti-nutritional factors can be removed, the product quality is guaranteed through the process, and the goose immunity is improved through multiple ways.

Description

Technical Field

[0001] This invention belongs to the field of poultry and livestock feed technology, specifically relating to a compound feed for improving the immunity of geese and its preparation method. Background Technology

[0002] Goose farming is an important part of my country's livestock and poultry industry, with goose meat, eggs, and down having high economic value. In goose farming, the goose's immunity directly determines its survival rate, growth performance, and product quality. Low immunity makes geese susceptible to infection by pathogenic microorganisms (such as E. coli and avian influenza virus) and intestinal dysfunction (such as diarrhea and indigestion). This is especially true for goslings (1-3 weeks old), whose immature digestive systems and fragile intestinal barriers make them extremely resistant to nutritional factors and pathogens, resulting in even more pronounced immunity problems.

[0003] As the core carrier of geese's nutrient intake, feed quality directly affects their gut health and immunity. Current goose feed research focuses primarily on adding immune enhancers (such as probiotics, vitamin E, and selenium) or optimizing conventional nutrient ratios (such as protein-energy ratios), but neglects the root causes of damage to goose gut health and immunity caused by large-molecule anti-nutritional factors in feed. Commonly used goose feed ingredients (such as soybean meal, wheat bran, sorghum, and rapeseed meal) commonly contain non-starch polysaccharides (NSPs, such as β-glucan and arabinoxylan), phytic acid, condensed tannins, phytohemagglutinins, and other anti-nutritional factors, among which large-molecule anti-nutritional factors (molecular weight > 100) are particularly problematic. The harm caused by large molecules (such as high-molecular-weight NSP, phytohemagglutinins, and polytannins) is particularly significant: On the one hand, these large molecules are difficult for goose intestinal digestive enzymes to break down, forming highly viscous chyme in the intestines, which hinders the contact between small molecule nutrients (amino acids, minerals, vitamins) and the intestinal mucosa, leading to a decrease in nutrient absorption efficiency (such as a 15%-30% reduction in protein digestibility and a 20%-25% reduction in calcium and phosphorus utilization). Long-term malnutrition directly weakens the goose's immune synthesis capacity (such as a reduction in the synthesis of immunoglobulin IgG and lysozyme); on the other hand, large molecule anti-nutritional factors can directly damage the intestinal barrier structure—for example, phytohemagglutinins can bind to glycoproteins on the surface of intestinal epithelial cells, leading to villus atrophy, crypt hyperplasia, and increased intestinal permeability, making it easier for pathogens and endotoxins to invade the body, inducing intestinal inflammatory responses, and thus activating the immune system to over-consume, which in turn reduces the goose's ability to resist infection.

[0004] To address the problem of anti-nutritional factors, existing technologies mainly employ the following approaches, but all have significant drawbacks: Enzyme addition method: This method involves adding xylanase, phytase, protease, etc. to the feed to degrade anti-nutritional factors. However, the activity of enzyme preparations is easily affected by feed processing (high-temperature pelleting at 80-120℃ leads to a 30%-50% loss of enzyme activity) and the intestinal environment (pH fluctuations, pepsin degradation). Furthermore, it can only target specific small molecule anti-nutritional factors (such as phytic acid and oligomeric NSP), and its degradation efficiency for large molecule anti-nutritional factors (such as high-molecular-weight tannins and phytohemagglutinins) is less than 20%, which cannot fundamentally eliminate their harm. Fermented feed method: This method utilizes microorganisms (such as lactic acid bacteria and yeast) to ferment and degrade anti-nutritional factors. However, the fermentation process is easily affected by strain activity, temperature, and substrate concentration, resulting in large differences in the degradation rate of anti-nutritional factors between batches (fluctuation range 20%-60%). Furthermore, the by-products produced during fermentation (such as organic acids and alcohols) may affect the palatability of the feed. At the same time, fermented feed has a short shelf life (<7 days at room temperature), which is not conducive to large-scale storage and transportation. Physical / chemical treatment methods: High-temperature puffing, acid and alkali soaking and other methods can destroy some anti-nutritional factors, but high temperature will cause a 10%-15% loss of heat-sensitive nutrients (such as B vitamins and amino acids) in the feed. Acid and alkali treatment can easily introduce chemical residues (such as sodium hydroxide residue from alkali treatment), which will irritate the intestinal mucosa of geese and aggravate intestinal damage. Raw material pretreatment method: The content of anti-nutritional factors is reduced by screening raw materials with low anti-nutritional factors (such as low-erucic acid rapeseed meal) or by removing the husk and shell. However, such raw materials are more expensive (15%-20% higher than conventional raw materials) and cannot completely remove large molecular anti-nutritional factors (such as 0.5%-1.0% of plant lectin residue after removing the husk from soybean meal). It is difficult to balance economy and effectiveness.

[0005] In summary, the current goose feed industry urgently needs a technical solution that can intercept and remove macromolecular anti-nutritional factors, protect intestinal health, and fundamentally improve the immunity of geese. Summary of the Invention

[0006] The purpose of this invention is to provide a compound feed for improving the immunity of geese and its preparation method, mainly to solve the technical problem that it is difficult to retain and remove large molecular anti-nutritional factors in existing goose feed, which leads to the inability of the goose intestine to absorb effective nutrients and ultimately causes low immunity in geese.

[0007] In a first aspect, the present invention provides a compound feed for improving the immunity of geese. This compound feed comprises the following components by weight: 30-50 parts wheat flour, 3-8 parts corn oil, 10-20 parts rice bran, 5-15 parts distiller's grains, 3-8 parts apple peel, 5-12 parts vinegar residue, 20-35 parts soybean meal, 0.5-2 parts modified chitosan, 0.3-1.5 parts modified dextran, and 0.1-0.5 parts probiotics. The modified chitosan is carboxymethyl cellulose-chitosan grafted with galactose, and the galactose and carboxymethyl cellulose-chitosan are linked by β-glycosidic bonds. The modified dextran is sodium alginate-dextran grafted with propylene glycol alginate. The modified chitosan and the modified dextran can cross-link in the small intestine of geese to form a complex with a pore size of 10-20 nm.

[0008] 1. Basic nutritional components: The basic nutritional components include: wheat flour, corn oil, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal.

[0009] Wheat flour: provides the carbohydrates needed for goose growth, and the gluten protein it contains can improve the stickiness of feed pellets and prevent breakage after pelleting; Corn oil: Rich in linoleic acid and vitamin E. Linoleic acid can promote the development of the goose's intestinal mucosa, and vitamin E can enhance the body's antioxidant capacity and reduce the damage of free radicals to immune cells. Rice bran, distiller's grains, and vinegar lees: These are agricultural by-products that are low in cost and rich in nutrients. Rice bran contains crude protein and dietary fiber, which together can promote intestinal peristalsis. Distiller's grains contain yeast protein and B vitamins, which can provide geese with abundant amino acids and nutrients. Vinegar lees contain acetic acid, which has a certain bactericidal effect and can inhibit the growth of harmful bacteria in the intestines. The three work together to improve the palatability and nutritional diversity of feed. Apple peel: Contains pectin, which can act as a prebiotic to promote the growth of beneficial bacteria in the goose's intestines, as well as flavonoids, which can be absorbed by geese, thereby enhancing their immunity. Crushing the apple peel and mixing it evenly with other components can avoid nutrient waste. Soybean meal: It is rich in protein and can serve as a high-quality source of plant protein. The essential amino acids it contains, such as lysine and methionine, can meet the needs of goose muscle growth and immunoglobulin synthesis.

[0010] 2. Modified chitosan: In the above-mentioned carboxymethyl cellulose-chitosan grafted with galactose, the carboxymethyl cellulose and chitosan are connected by hydrogen bonds, and the galactose is grafted onto the C2 amino group of the chitosan.

[0011] CTS is a deacetylated product of chitin, with glucosamine as its basic unit. Each glucosamine unit has an amino group at C2 and a hydroxyl group at both C3 and C6. The amino group at C2 is much more reactive than the hydroxyl group (amino groups are more nucleophilic) and is the preferred target for grafting reactions. The hemiacetal hydroxyl group at C1 of β-D-galactose can undergo a nucleophilic substitution reaction with the amino group at C2 of CTS to form a β-1,2-glycosidic bond. When the amino group at C2 of CTS is saturated, Gal can also be grafted onto the hydroxyl groups at C2 and C3 of CMC. However, this will consume some of the hydroxyl groups, resulting in a decrease in the binding force and pore size uniformity of the complex during subsequent cross-linking.

[0012] Carboxymethyl cellulose not only provides good water solubility for the complex and improves the overall stability of the feed, but it is also not easily degraded in the small intestine. The galactose grafted onto chitosan can only be hydrolyzed in the goose's large intestine, and is degraded by β-galactosidase secreted by bifidobacteria and other bacteria in the goose's large intestine. Therefore, the degradation of the whole modified chitosan in the small intestine is further avoided.

[0013] 3. Modified dextran: In the above-mentioned sodium alginate-dextran grafted with propylene glycol alginate, sodium alginate and dextran are connected by hydrogen bonds and ionic bonds, and propylene glycol alginate is grafted onto the C6 carboxyl group of sodium alginate.

[0014] The basic units of sodium alginate are guluronic acid (G unit) and mannuronic acid (M unit). Both units have one free carboxyl group at the C6 position and one hydroxyl group at the C2 and C3 positions. The C6 carboxyl group has the highest reactivity and is the preferred grafting site for PGA. The propylene glycol terminal hydroxyl group (-CH(OH)-CH3) of PGA undergoes an esterification reaction with the C6 carboxyl group (-COOH) of SA to form an ester bond. When the carboxyl group at the C6 position of SA is saturated, PGA can also be grafted onto the hydroxyl group at the C6 position of GL. However, this will consume some hydroxyl groups, resulting in a decrease in the binding force and pore size uniformity of the complex during subsequent cross-linking.

[0015] The α-L-guluronic acid bonds on sodium alginate can only be degraded by trehalase in the large intestine, and are not easily degraded in the small intestine. Similarly, glucan can only be degraded by β-glucanase secreted by Bifidobacterium in the goose's large intestine, thereby improving the overall biocompatibility of the modified glucan in the goose's small intestine. During degradation in the large intestine, esterase first hydrolyzes the ester bonds of PGA, destroying the cross-linking points, and then β-glucanase and cellulase degrade the SA and GL backbones. Finally, the molecular network disintegrates into small molecule oligosaccharides (molecular weight <1 kDa), with no risk of residue.

[0016] 4. Cross-linking of modified chitosan and modified dextran in goose small intestine: When modified chitosan and modified dextran are in the feed and the goose's stomach, the overall environment is slightly acidic and acidic, respectively. This slightly acidic and acidic environment can inhibit the linkage between the two by protonating the carboxyl groups. However, after entering the goose's small intestine, the overall reaction system is in a weakly alkaline environment. At this time, the amino group at the C2 position of the modified chitosan will be protonated to form -NH3. + The C6 carboxyl group of sodium alginate on the modified dextran will be deprotonated to form -COO. - -NH3 + With -COO - Electrostatic attraction forms ionic bonds between them, and these ionic bonds exhibit high uniformity: the amino groups of CTS and the carboxyl groups of SA are evenly distributed on the main chain, with approximately 1-2 active functional groups per 10 polysaccharide units. The formed ionic bonds are cross-linked in a network, avoiding excessively dense or sparse local cross-linking, ensuring that the overall pore size of the complex formed by the cross-linking is stable between 10-20 nm; and the small amount of -COO in CMC of the modified chitosan... - It can also react with trace protonated hydroxyl groups (-OH) in the PGA of the modified dextran. + The modified chitosan combines with ionic bonds to form weak ionic bonds, thereby further enhancing structural stability. Furthermore, hydrogen bonds are formed at multiple sites, such as the C3 hydroxyl group of the glucose unit on the CMC in the modified chitosan and the C6 hydroxyl group of the glucose unit on the GL in the modified dextran, and the hydroxyl group on the CTS in the modified chitosan and the hydroxyl group on the PGA in the modified dextran. Although the strength of hydrogen bonds is only 1 / 10 to 1 / 5 that of ionic bonds, it does not lead to excessive rigidity of the molecular network. Instead, it can deform slightly with intestinal peristalsis, avoiding mechanical shearing. Moreover, hydrogen bonds can further fill the gaps between ionic bonds, improving the pore size uniformity of the complex formed after cross-linking. This allows for the retention of large molecular anti-nutritional factors (such as phytohemagglutinins and polytannins) >120 kDa, while allowing small molecular nutrients (such as amino acids and glucose) <100 kDa to pass freely, ensuring that the small intestine absorbs only nutrients and preventing the absorption of anti-nutritional factors by the goose small intestine.

[0017] 5. Chain breaks of modified chitosan and modified dextran in goose large intestine: After entering the goose's large intestine, the intestinal flora secretes β-galactosidase (degrading Gal graft bonds) and carboxylesterase (degrading PGA ester bonds): the CTS backbone is cleaved by cellulase, and the positive potential point of the ionic bond (-NH3) + The SA backbone is reduced; the SA backbone is cleaved by trehalase, and the negative potential point of the ionic bond (-COO) is reduced. - )reduce; Ionic bonds gradually break, hydrogen bonds disappear naturally as the main chain degrades, and the molecular network disintegrates into small oligosaccharides, which are excreted with feces along with the retained large anti-nutritional factors, thus preventing the complex formed by the two from blocking the intestines and affecting the goose's metabolism.

[0018] Furthermore, the probiotics include one or more of Bifidobacterium animalis, Clostridium butyricum, Bacillus tekirae, and Enterobacter vesiculosus.

[0019] By adding the above-mentioned probiotics, highly active β-galactosidase and cellulase can be secreted, thereby improving the absorption of small molecule nutrients in the goose's small intestine. They can also assist in the degradation of crude fiber to prevent intestinal blockage, and assist in the degradation of complexes formed by cross-linking modified chitosan and modified dextran in the large intestine, promoting intestinal peristalsis and preventing intestinal blockage.

[0020] Secondly, the present invention provides a method for preparing the above-mentioned compound feed for improving the immunity of geese. The method includes the following steps: S1, preparing the modified chitosan; S2, preparing the modified dextran; S3, sieving the wheat flour, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal separately, and then crushing the apple peel; S4, mixing the sieved wheat flour, rice bran, distiller's grains, vinegar residue, and soybean meal with the crushed apple peel, pouring the mixture into a mixer, adding the corn oil, and starting the mixer to stir at 140-160 r / min for 15-20 minutes to obtain a basic mixture; S5, adding the modified chitosan and the modified dextran to the basic mixture, and continuing to stir at 110-130 r / min for 10-15 minutes to obtain a mixture; S6, after the mixture has naturally cooled to below 30°C, adding the probiotics, and then stirring at 70-90°C... S7. Stir at a speed of r / min for 5-8 minutes to obtain the final mixture; S8. Feed the final mixture into a pellet mill and press it into pellets at 60-70℃ with a pellet diameter of 3-5 mm to obtain wet pellets; S9. Place the wet pellets into a hot air drying oven and dry at 50-60℃ with an air speed of 1.2-1.8 m / s for 20-30 minutes to obtain dry pellets; S10. Allow the dry pellets to cool naturally to room temperature and then sieve them a second time to retain intact pellets, thus obtaining the compound feed for improving goose immunity.

[0021] The layered mixing of S3-S5 ensures uniform integration of function and nutrition: S3 uses sieving of basic raw materials (to remove impurities and uniform granulation) and crushing of apple peels (to release pectin and flavonoids) to lay a solid and uniform base for subsequent mixing; S4 uses high-speed stirring to allow corn oil (linoleic acid + vitamin E) to evenly coat the basic materials, ensuring that geese ingest essential nutrients and improving pelleting cohesion in conjunction with wheat flour gluten; S5 reduces the rotation speed to mix modified polysaccharides, avoiding high-speed damage to their cross-linked structure, while ensuring that each part of the feed contains sufficient functional components, avoiding the retention and ineffectiveness of anti-nutritional factors in local non-functional areas.

[0022] The combination of S6 probiotic activity and cooling / low speed: Add probiotics only after the mixture has cooled to below 30°C to avoid residual heat damaging the activity of Bifidobacterium animalis, Clostridium butyricum, etc.; low-speed stirring at 70-90 r / min ensures uniform dispersion of probiotics and prevents mechanical shearing damage to the bacteria, ensuring that the probiotics can normally secrete β-galactosidase and cellulase after entering the goose intestines. This not only assists in the degradation of modified polysaccharides in the large intestine (avoiding intestinal blockage) but also promotes the digestion of crude fiber and the absorption of small molecule nutrients, forming a synergistic effect of functional polysaccharides retaining anti-nutritional factors and probiotics optimizing the intestinal environment.

[0023] S7 (granulation) and S8 (drying) balance pellet stability and component activity: S7 uses low-temperature granulation at 60-70℃, which utilizes wheat flour gluten protein to ensure pellet formation (3-5 mm diameter, suitable for goose beak feeding, reducing spillage and waste), while avoiding high-temperature damage to heat-sensitive components such as vitamin E and probiotic spores; S8 uses hot air drying at 50-60℃ (wind speed 1.2-1.8 m / s, time 20-30 min) to control the moisture content to <12%, which prevents mold growth during feed storage (extending shelf life), avoids over-drying leading to pellet brittleness (protecting nutrients from loss), and maintains the structure / activity of modified polysaccharides and probiotics.

[0024] S9's natural cooling and secondary sieving ensure the final feeding effect: natural cooling avoids internal cracks in the pellets due to excessive temperature difference (preventing breakage during transportation), and secondary sieving with 4-6 mesh removes broken particles generated during pelleting / drying—ensuring uniform particle size in the finished product and preventing the loss of functional components and uneven nutrition from the broken particles, which can lead to differences in the effects of feeding on geese. Ultimately, each feed pellet can achieve a comprehensive effect of retaining anti-nutritional factors, supplementing nutrition, and optimizing the intestines, ensuring that the goose's intestines only absorb effective nutrients and excrete anti-nutritional factors. From improving nutrient absorption efficiency to optimizing the intestinal microenvironment, the goal of improving immunity is ultimately achieved.

[0025] In summary, steps S1-S9 are not isolated operations, but are interconnected: the first two steps ensure that the functional components can work, the middle three steps ensure that the components are mixed evenly and the activity is not lost, and the last four steps ensure that the feed can be stored, the geese can eat well, and the effect is achieved. The entire process revolves around solving core technical problems and improving the immunity of geese, achieving a unity of function, nutrition, palatability, and stability.

[0026] Further, step S1 specifically includes the following steps: S1.1, sieve and dry carboxymethyl cellulose powder to obtain CMC fines; sieve chitosan powder, soak it in a 1 wt% hydrochloric acid solution for 25-30 min, and then dry it to obtain CTS fines; S1.2, mix the CTS fines with deionized water, add 0.9-1.1 mol / L hydrochloric acid solution dropwise at 220-280 rpm to adjust the pH to 5.2-5.8, heat to a constant temperature water bath of 32-38℃, and stir until the CTS is completely dissolved to obtain a CTS solution. The mass-to-volume ratio of the CTS fines to the deionized water is 1 g:(75-85 mL); S1.3, maintaining the temperature and rotation speed of step S1.2, slowly add the CMC fines to the CTS solution in multiple portions, with an interval of 8-12 min between each addition. After complete addition, stir for 1-2 hours until the solution viscosity is 800-1000 μL. S1.4. Add p-toluenesulfonic acid to the CMC-CTS composite solution and stir until the pH of the solution drops to 4.5-5.0. The mass ratio of p-toluenesulfonic acid to β-D-galactose is (0.15-0.20):1. S1.5. Heat to 50℃ and add β-D-galactose in multiple portions, with an interval of 12-18 min between each addition. After complete addition, seal the container and stir at 180-220 rpm for 4-5 hours. Detect the content of free β-D-galactose. The mass ratio of β-D-galactose to CTS fines is (0.2-0.4):1. S1.6. When the free β-D-galactose content < 0.3... Stop the reaction when the concentration of the modified chitosan reaches g / L, adjust the pH to 6.8-7.2, and obtain the crude CMC-CTS-Gal solution; S1.7, slowly pour the crude CMC-CTS-Gal solution into 3 times its volume of 95 wt% ethanol solution while stirring, and let it stand for 25-35 min until no excess white precipitate is formed; S1.8, collect the precipitate after filtration, wash it several times with 95 wt% ethanol solution until the washing solution is negative when tested with p-toluenesulfonic acid test paper; S1.9, dry the washed precipitate for 10-15 hours to constant weight, then crush and sieve it to obtain the modified chitosan.

[0027] This refined process, through precise control of raw material pretreatment, reaction conditions, and purification, ensures that modified chitosan (CMC-CTS-Gal) possesses the core performance of efficiently retaining large molecular anti-nutritional factors. Specific benefits include: Raw material activation and purification: CTS in S1.1 is soaked in 1 wt% hydrochloric acid to activate the C2 amino group, thereby enhancing the activity of subsequent grafting reactions; CMC and CTS are sieved and dried to remove impurities and moisture, so as to avoid affecting the uniformity of the reaction and lay the foundation for high-quality composite solution.

[0028] Precise temperature control of reaction conditions: S1.2 Control pH 5.2-5.8, temperature 32-38℃, and solid-liquid ratio to ensure complete dissolution of CTS and appropriate concentration, avoiding uneven reaction caused by clumping or improper concentration; S1.3 Add CMC in portions and control viscosity to 800-1000 ml. This allows CMC and CTS to fully form hydrogen bonds, ensuring the stability of the composite solution and preventing component stratification.

[0029] Grafting efficiency and purity assurance: S1.4 Use p-toluenesulfonic acid to construct an acidic catalytic environment to promote the nucleophilic substitution reaction between β-D-galactose and CTS amino groups; S1.5 Add β-D-galactose in portions and check the free content <0.3 g / L to ensure sufficient grafting and preferential binding to CTS active sites, reduce the consumption of CMC hydroxyl groups, and avoid subsequent degradation of crosslinking performance; S1.6 Adjust the pH to neutral to terminate the reaction and protect the formed molecular structure.

[0030] Safe purification and dispersibility optimization: S1.7-S1.8 Precipitate and wash with ethanol to remove unreacted small molecule impurities and catalysts, and avoid residual components from damaging the goose's intestinal microenvironment; S1.9 Dry, pulverize and sieve to obtain uniform powder particles, ensuring that it is fully dispersed with the feed base components and that the content of functional components in each part of the feed is consistent.

[0031] Further, step S2 specifically includes the following steps: S2.1, sieve and dry sodium alginate powder to obtain SA fines; dissolve dextran powder in deionized water, filter through a 0.45 μm filter membrane, and concentrate under reduced pressure to obtain GL concentrate, wherein the mass-to-volume ratio of dextran powder to deionized water is 1 g:(19-21 mL); S2.2, add the SA fines to deionized water, and stir at 180-220 rpm at room temperature until the SA is completely dissolved and the solution viscosity is 300-400 mPa·s to obtain an SA solution, wherein the mass-to-volume ratio of SA fines to deionized water is 1 g:(55-65 mL); S2.3, slowly add the GL concentrate dropwise to the SA solution at a rate of 0.9-1.1 mL, and after the addition is complete, raise the temperature to 30°C and maintain the stirring speed in step S2.2 for 2 hours to obtain an SA-GL composite solution, wherein the viscosity of the SA-GL composite solution is 600-800 mPa·s. Pa·s; S2.4, Maintaining the temperature and rotation speed of the SA-GL composite solution in S2.3, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, stirring until the solution pH is 5.5-6.0 to obtain a mixed solution. The molar ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to N-hydroxysuccinimide is (1.1-1.3):1, and the mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide to SA fines is (0.06-0.10):1; S2.5, Dissolve propylene glycol alginate powder in deionized water, filter through a 0.45 μm filter membrane, and then dilute at 0.9-1.1 ppm. Slowly add mL of the solution to the mixture, seal the container after addition, and maintain the temperature and stirring speed in step S2.3 for 2.5-3.5 hours to obtain a crude SA-GL-PGA solution; S2.6, slowly pour the crude SA-GL-PGA solution into 4 times its volume of acetone while stirring, and let it stand for 15-25 minutes until no excess white precipitate forms; S2.7, collect the precipitate by filtration, wash it several times with acetone until the total residual amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide in the washing solution is <0.05 wt%; S2.8, dry the washed precipitate for 10-15 hours to constant weight, then pulverize and sieve to obtain the modified dextran.

[0032] This refined process, through scientific raw material processing, reaction coupling, and purification, prepares a modified dextran (SA-GL-PGA) that can precisely cross-link with modified chitosan. The specific benefits are as follows: Raw material pretreatment and purification: In S2.1, SA is sieved, dried, and impurities are removed. GL is filtered to remove insoluble impurities and concentrated under reduced pressure to increase concentration, avoiding incomplete reactions caused by low-purity raw materials and ensuring stable carboxyl-hydroxyl linkage between SA and GL. Composite solution stability control: In S2.2, the solid-liquid ratio and viscosity of SA are controlled at 300-400. Ensure the SA solution is homogeneous and has suitable fluidity to avoid clumping; S2.3 slowly drips the GL concentrate, controlling the temperature at 30℃ and the viscosity at 600-800. This process ensures that SA and GL undergo a thorough dehydration condensation reaction, preventing uneven compounding caused by localized over-addition. Grafting efficiency and structural protection: In step S2.4, EDC-NHS coupling agent (molar ratio 1.1-1.3:1) is added and the pH is controlled at 5.5-6.0 to activate the C6 carboxyl group of SA, significantly improving the esterification reaction efficiency with PGA. In step S2.5, the filtered PGA is slowly dripped and stirred in a sealed container to ensure that PGA preferentially grafts onto the active sites of SA, reducing the consumption of GL hydroxyl groups and preventing air oxidation from damaging the molecular structure. Safe purification and dispersibility assurance: Steps S2.6-S2.7 involve precipitation and washing with acetone to remove residual coupling agents such as EDC and NHS (total residual amount <0.05wt%), preventing irritation to the goose's intestinal mucosa. Step S2.8 involves drying, pulverizing, and sieving to obtain a uniform powder, ensuring uniform dispersion with the base material and providing a structural basis for forming a 10-20nm pore size network of ionic bonds with modified chitosan.

[0033] Furthermore, the screen mesh size for the first sieve is 10-15 mesh, and the screen mesh size for the second sieve is 4-6 mesh.

[0034] First-pass sieving (10-15 mesh): For basic nutritional components such as wheat flour and rice bran, this pore size can remove large particulate impurities in the raw materials (such as broken rice husks and clumps of soybean meal), ensuring the purity of the basic components. It can also make the particle size of each component uniform, avoiding the aggregation of local components during subsequent mixing due to particle differences (such as the separation of high-protein soybean meal and high-fiber rice bran). This lays the foundation for the uniform mixing of basic materials with corn oil, modified polysaccharides, and probiotics.

[0035] Secondary sieving (4-6 mesh): For dried pelleted feed, this pore size can remove broken particles generated during pelleting and drying, leaving whole particles with uniform particle size (suitable for goose beak feeding size), avoiding uneven nutrition caused by broken particles (functional components in broken particles are easily lost) and goose rejection of feeding, ensuring that the nutritional ratio of each feed pellet in the final product is consistent, and stably exerting the effect of improving goose immunity.

[0036] Beneficial effects of the present invention 1. Balanced nutrition and controllable cost: The basic components are scientifically formulated. Wheat flour provides carbohydrates and enhances the cohesiveness of feed pellets with the help of gluten protein. Corn oil contains linoleic acid (which helps the development of the intestinal mucosa) and vitamin E (which reduces damage to immune cells). Soybean meal provides high-quality plant protein and essential amino acids (which support the synthesis of immunoglobulins), fully meeting the growth and immune needs of geese. At the same time, agricultural by-products such as rice bran (which promotes intestinal peristalsis), distillers' grains (which supplement amino acids and B vitamins), and vinegar residues (which inhibit harmful bacteria in the intestines) are incorporated, which can reduce feed costs while enriching the variety of nutrients and improving palatability.

[0037] 2. Overcoming the Challenge of Anti-nutritional Factors: Modified chitosan and modified dextran work synergistically to form a stable (10-20 nm) network complex in the weakly alkaline environment of the goose small intestine through ionic and hydrogen bonds. This complex can retain large-molecule anti-nutritional factors (such as phytohemagglutinins) >120 kDa while allowing small-molecule nutrients (such as amino acids and glucose) <100 kDa to pass through normally. This prevents anti-nutritional factors from binding to sugar and amino acid receptors in small intestinal cells, thus affecting absorption. After entering the large intestine, the complex is broken down into small-molecule oligosaccharides by β-galactosidase and carboxylesterase secreted by intestinal flora, and excreted with the anti-nutritional factors without residue. The accompanying probiotics (such as Bifidobacterium animalis) can also secrete enzymes to assist in the degradation of the complex and the digestion of crude fiber, further optimizing the intestinal microenvironment and preventing intestinal blockage.

[0038] 3. Enhance goose immunity through multiple pathways: On the one hand, optimize nutrient absorption efficiency to provide a material basis for goose immune function; on the other hand, strengthen the intestinal health barrier, linoleic acid promotes intestinal mucosal development, vinegar residue and probiotics synergistically inhibit harmful bacteria, pectin promotes the proliferation of probiotics; in addition, the effects of vitamin E (antioxidant to protect immune cells), flavonoids (directly enhance immunity), and soybean protein (synthesize immunoglobulins) enhance goose immunity in multiple dimensions and reduce the risk of disease. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is an electron microscope image of the goose small intestine feed in Experiment Example 3 of the present invention; Figure 2 The image shows HE staining of goose small intestine in Experiment Example 4 of the present invention, where (a) is the staining result of Example 3 group and (b) is the result of Comparative Example 4 group; Figure 3This is a GPC elution curve of the contents of goose small intestine and large intestine in group 3 of test example 5 of the present invention; Figure 4 This is a GPC elution curve of the contents of goose small intestine and large intestine in group 9 of test example 5 of the present invention; Figure 5 This is a diagram illustrating the procedure for collecting blood from the subwing vein of a goose in Experiment Example 2 of this invention. Figure 6 This is a schematic diagram of the goose farming situation in Experiment Example 1 of the present invention; Figure 7 This is a diagram of normal goose feces in Experiment Example 2 of the present invention; Figure 8 This is a diagram of the feces of geese experiencing diarrhea in Experiment Example 2 of this invention. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element, wherein all materials used in this invention not expressly specified are commercially available.

[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0044] Example 1 1. Raw material components 30 kg wheat flour, 3 kg corn oil, 10 kg rice bran, 5 kg distiller's grains, 3 kg apple peel, 5 kg vinegar residue, 20 kg soybean meal, 0.5 kg modified chitosan, 0.3 kg modified dextran, and 0.1 kg probiotics (Bifidobacterium animalis). 2. Preparation method S1 Preparation of Modified Chitosan S1.1: Carboxymethyl cellulose powder was sieved and dried to obtain fine CMC; chitosan powder was sieved, soaked in 1 wt% hydrochloric acid for 25 min, and dried to obtain fine CTS. S1.2: Fine CTS was mixed with deionized water at a ratio of 1 g: 75 mL, and 0.9 mol / L hydrochloric acid was added dropwise at 220 rpm to adjust the pH to 5.2. The mixture was then heated to a constant temperature water bath at 32℃ and stirred until the CTS was completely dissolved to obtain a CTS solution. S1.3: Maintaining a temperature of 32℃ and a rotation speed of 220 rpm, fine CMC (mass ratio of fine CMC to fine CTS 1:1) was added to the CTS solution in multiple portions, with 8 min intervals between each addition. After the addition was complete, the mixture was stirred for 1 h until the viscosity reached 800. The CMC-CTS composite solution was obtained. S1.4: Add p-toluenesulfonic acid (0.15:1 mass ratio to galactose) and stir until pH 4.5. S1.5: Heat to 50℃, add β-D-galactose (0.2:1 mass ratio to CTS fines), at 12-min intervals, seal, and stir at 180 rpm for 4 h. Detect the free β-D-galactose content. S1.6: When free β-D-galactose < 0.3 g / L, adjust pH to 6.8 to obtain a crude CMC-CTS-Gal solution. S1.7: Pour 3 times the volume of 95 wt% ethanol into the crude solution, stir, and let stand for 25 min until no precipitate forms. S1.8: Filter the precipitate and wash with 95 wt% ethanol until the washing solution is negative on p-toluenesulfonic acid test paper. S1.9: Dry the precipitate for 10 h to constant weight, pulverize, and sieve to obtain modified chitosan.

[0045] S2 Preparation of Modified Dextran (Sodium Alginate-Dextran Grafted with Propylene Alginate) S2.1: Sodium alginate powder was sieved and dried to obtain SA fines; dextran was dissolved in deionized water at a ratio of 1 g:19 mL, filtered through a 0.45 μm filter membrane, and concentrated under reduced pressure to obtain GL concentrate. S2.2: SA fines were mixed with deionized water at a ratio of 1 g:55 mL, stirred at 180 rpm at room temperature until dissolved, with a viscosity of 300... SA solution was obtained. S2.3: The GL concentrate was added dropwise to the SA solution at a rate of 0.9 mL / min. After the addition was complete, the temperature was raised to 30°C, and the solution was stirred at 180 rpm for 2 hours to obtain a solution with a viscosity of 600. SA-GL composite solution. S2.4: Add EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide) and NHS (N-hydroxysuccinimide), with a molar ratio of EDC to NHS of 1.1:1 and a mass ratio of EDC to SA fines of 0.06:1, and stir until pH 5.5. S2.5: Add propylene glycol alginate solution (0.45 μm filtered) dropwise at 0.9 mL / min, seal, and stir at 30℃ and 180 rpm for 2.5 h to obtain crude SA-GL-PGA solution. S2.6: Pour 4 times the volume of acetone into the crude solution, stir, and let stand for 15 min until no precipitate remains. S2.7: Filter the precipitate, wash with acetone, and then use HPLC to determine that the total residual amount of EDC and NHS is 0.02 wt%, less than 0.05 wt%, which meets the requirements. S2.8: Dry the precipitate for 10 h to constant weight, pulverize and sieve to obtain modified dextran. S3-S9 Feed Preparation S3: Wheat flour, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal are sieved through a 10-mesh sieve once, and the apple peel is crushed. S4: The above raw materials are mixed with corn oil and stirred at 140 r / min for 15 min to obtain a basic mixture. S5: Modified chitosan and modified dextran are added, and stirred at 110 r / min for 10 min to obtain a mixed material. S6: The mixture is cooled to below 30℃, probiotics are added, and stirred at 70 r / min for 5 min to obtain a final mixture. S7: Granulation is performed at 60℃ with a particle diameter of 3 mm to obtain wet pellets. S8: The mixture is dried at 50℃ with an air velocity of 1.2 m / s for 20 min to obtain dry pellets. The moisture content is tested according to GB / T 6435-2014 "Determination of Moisture in Feed," and the measured moisture content is 8.4%, less than 12%, which meets the standard. S9: After cooling to room temperature, the mixture is sieved through a 4-mesh sieve a second time, retaining intact pellets to obtain a compound feed.

[0046] Example 2 1. Raw material components 50 kg wheat flour, 8 kg corn oil, 20 kg rice bran, 15 kg distiller's grains, 8 kg apple peel, 12 kg vinegar residue, 35 kg soybean meal, 2 kg modified chitosan, 1.5 kg modified dextran, and 0.5 kg probiotics (0.25 kg Bifidobacterium animalis and 0.25 kg Clostridium butyricum).

[0047] 2. Preparation method S1 Preparation of Modified Chitosan S1.1: Carboxymethyl cellulose (CMC) powder was sieved and dried to obtain fine CMC. Chitosan powder was sieved, soaked in 1 wt% hydrochloric acid for 30 min, and dried to obtain fine CTS. S1.2: Fine CTS was mixed with deionized water at a ratio of 1 g: 85 mL. 1.1 mol / L hydrochloric acid was added dropwise at 280 rpm to adjust the pH to 5.8. The mixture was then heated to a constant temperature water bath at 38℃ and stirred until the CTS was completely dissolved, yielding a CTS solution. S1.3: Maintaining a temperature of 38℃ and a rotation speed of 280 rpm, fine CMC (in a mass ratio of 1.5:1 to fine CTS) was added to the CTS solution in multiple portions, with 12 min intervals between each addition. After the addition was complete, the mixture was stirred for 2 h until the viscosity reached 1000. The CMC-CTS composite solution was obtained. S1.4: Add p-toluenesulfonic acid (0.20:1 mass ratio to galactose) and stir until pH 5.0. S1.5: Heat to 50℃, add β-D-galactose (0.4:1 mass ratio to CTS fines), at 18-min intervals, seal, and stir at 220 rpm for 5 h. Detect the free β-D-galactose content. S1.6: When free β-D-galactose < 0.3 g / L, adjust pH to 7.2 to obtain a crude CMC-CTS-Gal solution. S1.7: Pour 3 times the volume of 95 wt% ethanol into the crude solution, stir, and let stand for 35 min until no precipitate forms. S1.8: Filter the precipitate and wash with 95 wt% ethanol until the washing solution is negative on p-toluenesulfonic acid test paper. S1.9: Dry the precipitate for 15 h to constant weight, pulverize, and sieve to obtain modified chitosan.

[0048] S2 Preparation of Modified Dextran (Sodium Alginate-Dextran Grafted with Propylene Alginate) S2.1: Sodium alginate powder was sieved and dried to obtain SA fines; dextran was dissolved in deionized water at a ratio of 1 g: 21 mL, filtered through a 0.45 μm filter membrane, and concentrated under reduced pressure to obtain GL concentrate. S2.2: SA fines were mixed with deionized water at a ratio of 1 g: 65 mL, stirred at 220 rpm at room temperature until dissolved, with a viscosity of 400. SA solution was obtained. S2.3: The GL concentrate was added dropwise to the SA solution at a rate of 1.1 mL / min. After the addition was complete, the temperature was raised to 30℃, and the mixture was stirred at 220 rpm for 2 h to obtain a solution with a viscosity of 800. SA-GL composite solution. S2.4: Add EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide) and NHS (N-hydroxysuccinimide), with a molar ratio of EDC to NHS of 1.3:1 and a mass ratio of EDC to SA fines of 0.10:1, and stir until pH 6.0. S2.5: Add propylene glycol alginate solution (0.45 μm filtered) dropwise at 1.1 mL / min, seal, and stir at 30℃ and 220 rpm for 3.5 h to obtain crude SA-GL-PGA solution. S2.6: Pour 4 times the volume of acetone into the crude solution, stir, and let stand for 25 min until no precipitate remains. S2.7: Filter the precipitate, wash with acetone, and then use HPLC to determine that the total residual amount of EDC and NHS is 0.02 wt%, which is less than 0.05 wt%, meeting the requirements. S2.8: Dry the precipitate for 15 h to constant weight, pulverize and sieve to obtain modified dextran.

[0049] S3-S9 Feed Preparation S3: Wheat flour, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal are sieved through a 15-mesh sieve once, and the apple peel is crushed. S4: The above raw materials are mixed with corn oil and stirred at 160 r / min for 20 min to obtain a basic mixture. S5: Modified chitosan and modified dextran are added, and stirred at 130 r / min for 15 min to obtain a mixed material. S6: The mixture is cooled to below 30℃, probiotics are added, and stirred at 90 r / min for 8 min to obtain a final mixture. S7: Granulation is performed at 70℃ with a particle diameter of 5 mm to obtain wet pellets. S8: The mixture is dried at 60℃ with an air velocity of 1.8 m / s for 30 min to obtain dry pellets. The moisture content is tested according to GB / T6435-2014 "Determination of Moisture in Feed," and the measured moisture content is 6.7%, less than 12%, which meets the standard. S9: After cooling to room temperature, the mixture is sieved through a 6-mesh sieve a second time, retaining intact pellets to obtain a compound feed.

[0050] Example 3 1. Raw material components 40 parts wheat flour, 5.5 parts corn oil, 15 parts rice bran, 10 parts distiller's grains, 5.5 parts apple peel, 8.5 parts vinegar residue, 27.5 parts soybean meal, 1.25 parts modified chitosan, 0.9 parts modified dextran, and 0.3 parts probiotics (0.15 kg of Enterobacter sieboldii and 0.15 kg of Bacillus tekirae).

[0051] 2. Preparation method S1 Preparation of Modified Chitosan S1.1: Carboxymethyl cellulose (CMC) powder was sieved and dried to obtain CMC fines; chitosan powder was sieved, soaked in 1 wt% hydrochloric acid for 27.5 min, and dried to obtain CTS fines. S1.2: CTS fines were mixed with deionized water at a ratio of 1 g: 80 mL. 1.0 mol / L hydrochloric acid was added dropwise at 250 rpm to adjust the pH to 5.5. The mixture was then heated to a constant temperature water bath at 35°C and stirred until the CTS was completely dissolved to obtain a CTS solution. S1.3: Maintaining a temperature of 35°C and a rotation speed of 250 rpm, CMC fines (mass ratio of CMC to CTS fines 1.25:1) were added to the CTS solution in multiple portions, with 10 min intervals between each addition. After the addition was complete, the mixture was stirred for 1.5 h until the viscosity reached 900 μL. The CMC-CTS composite solution was obtained. S1.4: Add p-toluenesulfonic acid (mass ratio of 0.175:1 to galactose) and stir until pH 4.75. S1.5: Heat to 50℃, add β-D-galactose (mass ratio of 0.3:1 to CTS fines), at 15-min intervals, seal, and stir at 200 rpm for 4.5 h. Detect the free β-D-galactose content. S1.6: When free β-D-galactose < 0.3 g / L, adjust pH to 7.0 to obtain a crude CMC-CTS-Gal solution. S1.7: Pour 3 times the volume of 95 wt% ethanol into the crude solution, stir, and let stand for 30 min until no precipitate forms. S1.8: Filter the precipitate and wash with 95 wt% ethanol until the washing solution is negative on p-toluenesulfonic acid test paper. S1.9: Dry the precipitate for 12.5 h to constant weight, pulverize, and sieve to obtain modified chitosan.

[0052] S2 Preparation of Modified Dextran (Sodium Alginate-Dextran Grafted with Propylene Alginate) S2.1: Sodium alginate powder was sieved and dried to obtain SA fines; dextran was dissolved in deionized water at a ratio of 1g:20mL, filtered through a 0.45μm filter membrane, and concentrated under reduced pressure to obtain GL concentrate. S2.2: SA fines were mixed with deionized water at a ratio of 1g:60mL, stirred at 200rpm at room temperature until dissolved, with a viscosity of 350. SA solution was obtained. S2.3: The GL concentrate was added dropwise to the SA solution at a rate of 1.0 mL / min. After the addition was complete, the temperature was raised to 30°C, and the mixture was stirred at 200 rpm for 2 hours to obtain a solution with a viscosity of 700. SA-GL composite solution. S2.4: Add EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide) and NHS (N-hydroxysuccinimide), with a molar ratio of EDC to NHS of 1.2:1 and a mass ratio of EDC to SA fines of 0.08:1, and stir until pH 5.75. S2.5: Add propylene glycol alginate solution (0.45μm filtered) dropwise at 1.0mL / min, seal, and stir at 30℃ and 200rpm for 3.0h to obtain crude SA-GL-PGA solution. S2.6: Pour 4 times the volume of acetone into the crude solution, stir, and let stand for 20min until no precipitate remains. S2.7: Filter the precipitate, wash with acetone, and then use HPLC to determine that the total residual amount of EDC and NHS is 0.01wt%, which is less than 0.05wt%, meeting the requirements. S2.8: Dry the precipitate for 12.5h to constant weight, pulverize and sieve to obtain modified dextran.

[0053] S3-S9 Feed Preparation S3: Wheat flour, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal are sieved through a 12.5 mesh sieve once, and the apple peel is crushed. S4: The above raw materials are mixed with corn oil and stirred at 150 rpm for 17.5 min to obtain the basic mixture. S5: Modified chitosan and modified dextran are added, and stirred at 120 rpm for 12.5 min to obtain the final mixture. S6: The mixture is cooled to below 30℃, probiotics are added, and stirred at 80 rpm for 6.5 min to obtain the final mixture. S7: Pelletize at 65℃ with a particle diameter of 4 mm to obtain wet pellets. S8: Dry at 55℃ with an air velocity of 1.5 m / s for 25 min to obtain dry pellets. The moisture content is tested according to GB / T6435-2014 "Determination of Moisture in Feed," and the measured moisture content is 7.7%, less than 12%, which meets the standard. S9: After cooling to room temperature, the mixture is sieved through a 5 mesh sieve a second time, retaining intact pellets to obtain the compound feed.

[0054] Example 4 1. Raw material components 45 kg wheat flour, 6.75 kg corn oil, 17.5 kg rice bran, 12.5 kg distiller's grains, 6.75 kg apple peel, 10.25 kg vinegar residue, 31.25 kg soybean meal, 1.625 kg modified chitosan, 1.2 kg modified dextran, and 0.4 kg probiotics (0.2 kg Bifidobacterium animalis and 0.2 kg Enterobacter vesiculosus).

[0055] 2. Preparation method S1 Preparation of Modified Chitosan S1.1: Carboxymethyl cellulose (CMC) powder was sieved and dried to obtain fine CMC. Chitosan powder was sieved, soaked in 1 wt% hydrochloric acid for 28.75 min, and dried to obtain fine CTS. S1.2: Fine CTS was mixed with deionized water at a ratio of 1 g: 82.5 mL. 1.05 mol / L hydrochloric acid was added dropwise at 265 rpm to adjust the pH to 5.65. The mixture was heated to 36.5℃ and kept in a constant temperature water bath, stirring until the CTS was completely dissolved to obtain a CTS solution. S1.3: Maintaining a temperature of 36.5℃ and a rotation speed of 265 rpm, fine CMC (in a mass ratio of 1.375:1 to fine CTS) was added to the CTS solution in multiple portions, with 11 min intervals between each addition. After the addition was complete, the mixture was stirred for 1.75 h until the viscosity reached 950. The CMC-CTS composite solution was obtained. S1.4: Add p-toluenesulfonic acid (mass ratio of 0.1875:1 to galactose) and stir until pH 4.875. S1.5: Heat to 50℃, add β-D-galactose (mass ratio of 0.35:1 to CTS fines), at 16.5 min intervals, seal, and stir at 210 rpm for 4.75 h. Detect the free β-D-galactose content. S1.6: When free β-D-galactose < 0.3 g / L, adjust pH to 7.1 to obtain crude CMC-CTS-Gal solution. S1.7: Pour 3 times the volume of 95 wt% ethanol into the crude solution, stir, and let stand for 32.5 min until no precipitate remains. S1.8: Filter the precipitate and wash with 95 wt% ethanol until the washing solution is negative on p-toluenesulfonic acid test paper. S1.9: Dry the precipitate for 13.75 h to constant weight, pulverize, and sieve to obtain modified chitosan.

[0056] S2 Preparation of Modified Dextran (Sodium Alginate-Dextran Grafted with Propylene Alginate) S2.1: Sodium alginate powder was sieved and dried to obtain SA fines; dextran was dissolved in deionized water at a ratio of 1g:20.5mL, filtered through a 0.45μm filter membrane, and concentrated under reduced pressure to obtain GL concentrate. S2.2: SA fines were mixed with deionized water at a ratio of 1g:62.5mL, stirred at 210rpm at room temperature until dissolved, with a viscosity of 375. SA solution was obtained. S2.3: The GL concentrate was added dropwise to the SA solution at a rate of 1.05 mL / min. After the addition was complete, the temperature was raised to 30°C, and the mixture was stirred at 210 rpm for 2 hours to obtain a solution with a viscosity of 750. SA-GL composite solution. S2.4: Add EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide) and NHS (N-hydroxysuccinimide), with a molar ratio of EDC to NHS of 1.25:1 and a mass ratio of EDC to SA fines of 0.09:1, and stir until pH 5.875. S2.5: Add propylene glycol alginate solution (0.45μm filtered) dropwise at 1.05mL / min, seal, and stir at 30℃ and 210rpm for 3.25h to obtain crude SA-GL-PGA solution. S2.6: Pour 4 times the volume of acetone into the crude solution, stir, and let stand for 22.5min until no precipitate remains. S2.7: Filter the precipitate, wash with acetone, and then use HPLC to determine that the total residual amount of EDC and NHS is 0.03wt%, which is less than 0.05wt%, meeting the requirements. S2.8: Dry the precipitate for 13.75h to constant weight, pulverize and sieve to obtain modified dextran.

[0057] S3-S9 Feed Preparation S3: Wheat flour, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal are sieved through a 14-mesh sieve once, and the apple peel is crushed. S4: The above raw materials are mixed with corn oil and stirred at 155 rpm for 18.75 min to obtain the basic mixture. S5: Modified chitosan and modified dextran are added, and stirred at 125 rpm for 13.75 min to obtain the final mixture. S6: The mixture is cooled to below 30℃, probiotics are added, and stirred at 85 rpm for 7.25 min to obtain the final mixture. S7: Pelletize at 67.5℃ with a particle diameter of 4.5 mm to obtain wet pellets. S8: Dry at 57.5℃ with an air velocity of 1.65 m / s for 27.5 min to obtain dry pellets. The moisture content is tested according to GB / T6435-2014 "Determination of Moisture in Feed," and the measured moisture content is 8.5%, less than 12%, meeting the standard. S9: After cooling to room temperature, the mixture is sieved through a 5.5-mesh sieve a second time, retaining intact pellets to obtain the compound feed.

[0058] Example 5 1. Raw material components 35 kg wheat flour, 4.25 kg corn oil, 12.5 kg rice bran, 7.5 kg distiller's grains, 4.25 kg apple peel, 6.75 kg vinegar residue, 23.75 kg soybean meal, 0.875 kg modified chitosan, 0.6 kg modified dextran, and 0.2 kg probiotics (0.1 kg Bifidobacterium animalis and 0.1 kg Enterobacter vesiculosus).

[0059] 2. Preparation method S1 Preparation of Modified Chitosan S1.1: Carboxymethyl cellulose powder was sieved and dried to obtain CMC fines; chitosan powder was sieved and soaked in 1wt% hydrochloric acid for 26.25 min, then dried to obtain CTS fines. S1.2: CTS fines were mixed with deionized water at a ratio of 1 g: 77.5 mL. 0.95 mol / L hydrochloric acid was added dropwise at 235 rpm to adjust the pH to 5.35. The mixture was heated to 33.5℃ and kept in a constant temperature water bath, stirring until the CTS was completely dissolved to obtain a CTS solution. S1.3: Maintaining a temperature of 33.5℃ and a rotation speed of 235 rpm, CMC fines (mass ratio of CMC to CTS fines 1.125:1) were added to the CTS solution in multiple portions, with 9 min intervals between each addition. After the addition was complete, the mixture was stirred for 1.25 h until the viscosity reached 850. The CMC-CTS composite solution was obtained. S1.4: Add p-toluenesulfonic acid (mass ratio of 0.1625:1 to galactose) and stir until pH 4.625. S1.5: Heat to 50℃, add β-D-galactose (mass ratio of 0.25:1 to CTS fines), at 13.5 min intervals, seal, and stir at 190 rpm for 4.25 h. Detect the free β-D-galactose content. S1.6: When free β-D-galactose < 0.3 g / L, adjust pH to 6.9 to obtain a crude CMC-CTS-Gal solution. S1.7: Pour 3 times the volume of 95 wt% ethanol into the crude solution, stir, and let stand for 27.5 min until no precipitate remains. S1.8: Filter the precipitate and wash with 95 wt% ethanol until the washing solution is negative on p-toluenesulfonic acid test paper. S1.9: Dry the precipitate for 11.25 h to constant weight, pulverize, and sieve to obtain modified chitosan.

[0060] S2 Preparation of Modified Dextran (Sodium Alginate-Dextran Grafted with Propylene Alginate) S2.1: Sodium alginate powder was sieved and dried to obtain SA fines; dextran was dissolved in deionized water at a ratio of 1g:19.5mL, filtered through a 0.45μm filter membrane, and concentrated under reduced pressure to obtain GL concentrate. S2.2: SA fines were mixed with deionized water at a ratio of 1g:57.5mL, stirred at 190rpm at room temperature until dissolved, with a viscosity of 325. SA solution was obtained. S2.3: The GL concentrate was added dropwise to the SA solution at a rate of 0.95 mL / min. After the addition was complete, the temperature was raised to 30°C, and the solution was stirred at 190 rpm for 2 hours to obtain a solution with a viscosity of 650. SA-GL composite solution. S2.4: Add EDC (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide) and NHS (N-hydroxysuccinimide), with a molar ratio of EDC to NHS of 1.15:1 and a mass ratio of EDC to SA fines of 0.07:1, and stir until pH 5.625. S2.5: Add propylene glycol alginate solution (0.45μm filtered) dropwise at 0.95mL / min, seal, and stir at 30℃ and 190rpm for 2.75h ​​to obtain crude SA-GL-PGA solution. S2.6: Pour 4 times the volume of acetone into the crude solution, stir, and let stand for 17.5min until no precipitate remains. S2.7: Filter the precipitate, wash with acetone, and then use HPLC to determine that the total residual amount of EDC and NHS is 0.02wt%, which is less than 0.05wt%, meeting the requirements. S2.8: Dry the precipitate for 11.25h to constant weight, pulverize and sieve to obtain modified dextran.

[0061] S3-S9 Feed Preparation S3: Wheat flour, rice bran, distiller's grains, apple peel, vinegar residue, and soybean meal are sieved through an 11.25 mesh screen once, and the apple peel is crushed. S4: The above raw materials are mixed with corn oil and stirred at 145 rpm for 16.25 min to obtain the basic mixture. S5: Modified chitosan and modified dextran are added, and stirred at 115 rpm for 11.25 min to obtain the final mixture. S6: The mixture is cooled to below 30℃, probiotics are added, and stirred at 75 rpm for 5.75 min to obtain the final mixture. S7: Pelletize at 62.5℃ with a particle diameter of 3.5 mm to obtain wet pellets. S8: Dry at 52.5℃ with an air velocity of 1.35 m / s for 22.5 min to obtain dry pellets. The moisture content is tested according to GB / T6435-2014 "Determination of Moisture in Feed," and the measured moisture content is 9.3%, less than 12%, which meets the standard. S9: After cooling to room temperature, pass through a 4.5-mesh sieve twice to retain intact particles, thus obtaining compound feed.

[0062] Comparative Example 1 This comparative example is based on Example 1, except that the modified chitosan is replaced with ordinary chitosan, and the remaining components are prepared in the same way.

[0063] Comparative Example 2 This comparative example is based on Example 1, except that the modified dextran is replaced with ordinary dextran, and the remaining components are prepared in the same way.

[0064] Comparative Example 3 This comparative example is based on Example 1, without the addition of probiotics, and the remaining components are prepared in the same way as in Example 1.

[0065] Comparative Example 4 This comparative example uses commercially available ordinary goose feed (without immune-enhancing components).

[0066] Comparative Example 5 Based on Example 1, the modified chitosan was replaced with ordinary chitosan, the modified dextran was replaced with ordinary dextran, and the remaining components were prepared in the same way as in Example 1.

[0067] Experimental Example 1 300 one-day-old white-feathered goslings were purchased (from the same hatchery, healthy parents, hatching time difference <12 h, initial weight 35-40g, good mental state, no beak or foot deformities). Upon arrival at the laboratory, they were first raised in an isolation shed for 3 days (temperature 32℃, free access to 5 wt% glucose water + electrolyte multivitamins). Goslings with abnormal weight (<30 g or >45 g) or lethargy were culled, leaving 200 goslings for the experiment. These 200 goslings were divided into 10 groups, each with half males and half females, numbered 1-10. They were fed daily, in sequence, the goose feed prepared in Examples 1-5 and Comparative Examples 1-5. Nine groups served as controls, raised in cages. Environmental control: Temperature: 32℃ for 1-7 days, 30℃ for 8-14 days, 28℃ for 15-21 days (error ±1℃); Humidity: 60%-65% (monitored in real-time with a hygrometer; water was sprinkled on the ground when below 55%); Light: 16 8 hours of light (8:00-24:00) + 8 hours of darkness, light intensity 20-30 lux; ventilation: 3 air changes per hour, ensuring ammonia concentration <10 ppm, and aquaculture conditions as follows. Figure 6 As shown.

[0068] Feeding: 0-7 days old: 6 times a day (7:00, 10:00, 13:00, 16:00, 19:00, 22:00), each animal is fed 3-5 g each time (gradually increase), ensure that there is no leftover food in the feed trough, and provide free access to clean tap water (water temperature 25-30℃) throughout the entire process. Clean and disinfect the waterers daily.

[0069] Observe the goslings' mental state and fecal shape daily (normally formed, diarrheal feces are pasty), with fecal shape referring to... Figure 7 and Figure 8 As shown, record the number of deaths and the cause (if diseased geese are found, immediately dissect them and rule out infectious diseases).

[0070] Sample collection: (1) Fecal sample collection (5 samples were collected from each group at 14-day and 21-day age) Time: 8:00 AM before feeding (on an empty stomach to reduce interference from feed residue); Methods: Three goslings were randomly selected from each group and fresh feces (about 5 g per gosling) were collected with sterile cotton swabs and placed into 50 mL centrifuge tubes (labeled with group name, replicate, and date). Handling: Immediately place in a -80℃ ultra-low temperature freezer for storage (to avoid degradation of anti-nutritional factors), and conduct unified testing after sampling is completed at 21 days of age.

[0071] Detection of macromolecular anti-nutritional substances: 1. Phytohemagglutinins: Sample pretreatment: Take 0.5 g of frozen feces, add 5 mL of PBS buffer (pH 7.4), vortex for 1 min, centrifuge at 4℃ and 5000 rpm for 5 min, and take the supernatant and filter it through a 0.22 μm filter membrane (omitting multiple centrifugations, directly take the supernatant in one go).

[0072] Detection procedure: Follow the "3-step rapid method" in the kit instructions: (1) Add 100 μL of sample / standard to 96-well plate and incubate at 37℃ for 30 min (the original 1 h was shortened to 30 min, and the kit has been verified to not affect the accuracy); (2) After discarding the liquid, add the detection antibody and incubate at 37℃ for 20 min; (3) Add the substrate for color development for 10 min, and after termination, read the microplate reader at 450 nm.

[0073] Calculation: Use the standard curve provided with the kit to directly substitute the OD value to calculate the content.

[0074] 2. High-polymer tannins: Sample pretreatment: 0.5 g feces + 10 mL 70% acetone, sonicate for 20 min, centrifuge at 4000 rpm for 5 min at 4℃, and collect the supernatant.

[0075] Detection procedure: (1) Add 1 mL of supernatant, 0.5 mL of Folin reagent, and 1 mL of 10% Na2CO3 to a final volume of 10 mL; (2) Incubate in a 37℃ water bath for 20 min and measure the absorbance at 520 nm (use distilled water as a blank); (3) Use tannic acid standard (0.1-1.0 mg / mL) to create three gradient standard curves and substitute them into the curves to calculate the content.

[0076] The retention rate of each group was calculated using the formula: Retention rate = (Anti-nutritional factor content in feces of groups 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 10 - Anti-nutritional factor content in feces of group 9) / Anti-nutritional factor content in feces of group 9 × 100%. The results are shown in Table 1.

[0077] Table 1 Calculation of Retention Rate Content

[0078] According to the results in Table 1, geese fed with the goose feed prepared in Examples 1-5 of this invention exhibited retention rates of over 35% and 45% for macromolecular anti-nutritional factors such as phytohemagglutinins and high-polymer tannins, respectively. In contrast, geese fed with the goose feed prepared in Comparative Examples 1, 2, and 5 showed no significant retention of macromolecular anti-nutritional factors. However, geese fed with the goose feed prepared in Comparative Example 3 showed a slight increase compared to the control group. This is presumably due to the low amount of probiotics added, which resulted in the incomplete degradation of some complexes, leading to their accumulation in the goose's intestines and their inability to be excreted.

[0079] Experimental Example 2: Detection of Goose Serum Immunoglobulins Test subjects: Same as in test example 1.

[0080] Detection method: On days 21 and 42 of the experiment, 10 geese were randomly selected from each group, and blood was collected from the subwing vein (procedure as follows). Figure 5 As shown in the figure, serum was separated, and the levels of IgG and IgA in the serum were detected by enzyme-linked immunosorbent assay (ELISA), and the average values ​​were calculated.

[0081] The results are shown in Table 2: Table 2. Serum IgG and IgA levels in each group

[0082] Results Analysis: As shown in Table 2, the IgA and IgG contents in geese fed with the goose feed prepared in Examples 1-5 were significantly higher than those in the goose feed prepared in Comparative Examples 1-5. Furthermore, the IgA and IgG contents in groups 1-5 and 8 increased by approximately 10% after 42 days, while the IgA and IgG contents in groups 6, 7, 9, and 10 did not show a significant increase after 42 days. Therefore, it can be seen that the goose feed prepared in the embodiments of the present invention can improve the absorption efficiency of nutrients by geese, thereby enhancing their immunity.

[0083] Experimental Example 3 One goose from Group 1 of Experiment 1 was fed at 8:00 AM on the day of euthanasia, and then placed in a carbon dioxide anesthesia chamber at 10:00 AM after feeding at 8:00 AM. The chamber was purged with 50% CO2 and 50% air for 5 minutes until respiration ceased (to avoid stress-induced changes in intestinal structure). Immediately after euthanasia, the goose was bled (from the jugular vein to avoid internal bleeding and blood contamination of the intestines). The abdomen was quickly dissected in a clean bench, and the entire small intestine (from the pylorus of the stomach to the cecal inlet) was removed. The outer wall of the small intestine was rinsed with pre-cooled 0.1 mol / L PBS buffer, and the rinsing fluid was collected. The rinsing fluid was centrifuged at 800 rpm, the supernatant was discarded, and the precipitate was observed under an electron microscope. The results are as follows: Figure 1 show.

[0084] according to Figure 1The results show that the pore size of the membrane network is approximately 10-20 nm, while the molecular diameter of polymerized tannins is approximately 18-25 nm, and the hydrodynamic diameter of phytohemagglutinins is approximately 25-30 nm. The 10-20 nm pore size can effectively trap these large molecular anti-nutritional factors. The diameters of small molecular nutrients, such as amino acids and glucose, are all below 2 nm, so they can effectively pass through the membrane network and be effectively absorbed by the small intestine in geese, thereby enhancing the goose's immunity.

[0085] Experimental Example 4: HE staining and morphological observation of goose small intestine tissue Test subjects: 10 geese raised in 3 groups in Experiment 1 and 10 geese raised in 9 groups in Experiment 1 were selected; Experimental steps: 1. Five geese were randomly selected from each group and slaughtered after fasting for 6 hours. The middle section of the small intestine (about 1 cm) was quickly separated, and the surface impurities were rinsed with pre-cooled PBS. The geese were then immediately placed in 10% neutral buffered formaldehyde fixative for 24 hours.

[0086] 2. Preparation of paraffin sections: After fixation, the tissue was dehydrated in a gradient (70% ethanol → 80% ethanol → 95% ethanol → anhydrous ethanol, 5 min each), cleared with xylene (xylene I and II, 15 min each), embedded in paraffin (60℃, 2 h), cut into 4 μm thick sections using a paraffin microtome, spread out and dried for later use.

[0087] 3. HE staining: Follow the standard procedure: Dewaxing (xylene I 15 min → xylene II 15 min → xylene: anhydrous ethanol = 1:12 min) → Rehydration (100% ethanol I and II 5 min each → 80% ethanol 5 min → distilled water 5 min) → Hematoxylin staining 5 min → Rinse with running water 10 min → Differentiation with 1% hydrochloric acid ethanol 30 s → Rinse with distilled water 5 s → 0.5% eosin staining 2 min → Rinse briefly with distilled water 30 s → Gradient dehydration (80% ethanol → 95% ethanol I and II → anhydrous ethanol I and II 3 min each) → Xylene clearing (I and II 3 min each) → Mounting with neutral resin.

[0088] Observation and photography: The height of small intestinal villi, crypt depth, and mucosal integrity of each group were observed under an optical microscope (100×, 400×). Five fields of view were randomly selected from each sample for photography, and a scale bar (50μm) was marked. The results are as follows: Figure 2 As shown.

[0089] according to Figure 2The results showed that in (a), the small intestinal villi were neatly and densely arranged, with a height of approximately 220 μm and a crypt depth of approximately 45 μm; in (b), the villi were atrophied and accompanied by villi breakage, with a height of approximately 50-80 μm and a crypt depth of approximately 100-120 μm. The left villi were neatly and densely arranged with sufficient height, which maximizes the absorption area of ​​nutrients, while the right villi were significantly atrophied and structurally incomplete, resulting in a significant decrease in absorption function. Furthermore, the left crypt depth was normal, and the mucosal layer structure was intact, ensuring the normal renewal and functional maintenance of intestinal epithelial cells. Due to structural damage, cell renewal and barrier function of the right mucosal layer may be impaired.

[0090] Experimental Example 5: Verification of the binding and degradation of the modified polysaccharide-antinutritional factor complex Test subject: Same as test case 4 Experimental steps: 1. Sample collection: Five geese were selected from each group after fasting for 6 hours before slaughter at 42 days of age. The middle section of the small intestine and the middle section of the large intestine were quickly separated, and the intestinal contents (about 0.5g) were collected separately. The contents were immediately placed in pre-cooled centrifuge tubes and transported to the laboratory on ice.

[0091] 2. Sample pretreatment: Add 5 mL of pre-cooled PBS to the intestinal contents, homogenize in an ice bath for 3 min (3000 rpm) using a tissue homogenizer, centrifuge at 12000 rpm for 15 min at 4℃, and collect the supernatant. Take 1 mL of the supernatant, add 3 mL of THF, vortex to mix for 10 min, incubate at 4℃ for 2 hours, centrifuge at 12000 rpm for 10 min, collect the supernatant and filter through a 0.22 μm organic phase filter membrane for later use.

[0092] 3. GPC testing conditions: Mobile phase: THF; Flow rate: 1.0 mL / min; Column temperature: 35℃; Injection volume: 50 μL; Detection wavelength: 254 nm.

[0093] Standard curve establishment: Prepare a series of concentration solutions using narrow-distribution polystyrene standards, and perform detection under the conditions described above. Establish a calibration curve (R0) with retention time as the x-axis and the logarithm of molecular weight as the y-axis. 2 ≥0.995).

[0094] 4. Sample Testing: The processed small and large intestine contents samples were subjected to GPC testing under the conditions described above. The elution curves were recorded, and the results are as follows: Figure 3 and Figure 4 As shown.

[0095] according to Figure 3The results showed that the elution curve of the small intestinal contents in group 3 showed a high molecular weight peak (molecular weight 120-180 kDa, corresponding to the modified polysaccharide-antinutritional factor complex) at a retention time of 8-10 min, while the elution curve of the large intestinal contents only showed a low molecular weight peak (molecular weight 500-800 Da, corresponding to the degraded oligosaccharide) at a retention time of 15-17 min. according to Figure 4 The results showed that the elution curves of the small intestinal contents and the large intestinal contents in group 9 did not have high molecular weight peaks, but only low molecular weight impurity peaks.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A compound feed for enhancing the immunity of geese, characterized in that: Includes the following components, calculated in parts by weight: Wheat flour 30-50 parts, corn oil 3-8 parts, rice bran 10-20 parts, distiller's grains 5-15 parts, apple peel 3-8 parts, vinegar residue 5-12 parts, soybean meal 20-35 parts, modified chitosan 0.5-2 parts, modified dextran 0.3-1.5 parts, probiotics 0.1-0.5 parts; The modified chitosan is carboxymethyl cellulose-chitosan grafted with galactose, and the galactose and the carboxymethyl cellulose-chitosan are linked by β-glycosidic bonds; the modified dextran is sodium alginate-dextran grafted with propylene glycol alginate. The modified chitosan and the modified dextran can cross-link in the small intestine of a goose to form a complex with a pore size of 10-20 nm.

2. The compound feed for improving goose immunity according to claim 1, characterized in that: The probiotics include one or more of Bifidobacterium animalis, Clostridium butyricum, Bacillus tekirae, and Enterobacter vesiculosus.

3. A method for preparing a compound feed for improving goose immunity as described in any one of claims 1 or 2, characterized in that: Includes the following steps: S1. The modified chitosan is prepared. S2. The modified dextran is prepared. S3. Take the wheat flour, rice bran, distiller's grains, apple peel, vinegar residue and soybean meal and sieve them one by one, then crush the apple peel; S4. Mix the sieved wheat flour, rice bran, distiller's grains, vinegar residue, and soybean meal with the crushed apple peel, then add the corn oil and stir well to obtain the basic mixture. S5. Add the modified chitosan and the modified dextran to the base mixture and stir well to obtain the mixture. S6. After the mixture has cooled naturally to below 30°C, add the probiotics and stir well to obtain the final mixture. S7. The final mixed material is fed into a pellet mill and pressed into pelleted feed to obtain wet pellets. S8. Place the wet granules in a hot air drying oven and dry for 20-30 minutes to obtain dry granules. S9. Allow the dried granules to cool naturally to room temperature, then sieve them a second time to retain intact granules, thus obtaining the compound feed that enhances the immunity of geese.

4. The method for preparing the compound feed for improving goose immunity according to claim 3, characterized in that: S1 specifically includes the following steps: S1.

1. Take carboxymethyl cellulose powder, sieve it and dry it to obtain CMC fines. Take chitosan powder, sieve it and soak it in hydrochloric acid solution for 25-30 minutes and then dry it to obtain CTS fines. S1.

2. Take the CTS fine material and mix it with deionized water. While stirring, add hydrochloric acid solution dropwise to adjust the pH to 5.2-5.

8. Keep the mixture in a constant temperature water bath and stir until the CTS is completely dissolved to obtain a CTS solution. S1.

3. Maintain the temperature and rotation speed in S1.2, and slowly add the CMC fines to the CTS solution in multiple portions, with an interval of 8-12 minutes between each addition. After complete addition, stir until the solution viscosity is 800-1000 mPa·s to obtain the CMC-CTS composite solution. S1.4 Add p-toluenesulfonic acid to the CMC-CTS composite solution and stir until the pH of the solution drops to 4.5-5.0; S1.

5. Heat to 50℃ and add the β-D-galactose in multiple portions, with an interval of 12-18 minutes between each addition. After complete addition, seal the container and stir for 4-5 hours. Then, detect the content of free β-D-galactose. S1.

6. When the free β-D-galactose content is <0.3 g / L, stop the reaction, adjust the pH to 6.8-7.2, and obtain the crude CMC-CTS-Gal solution; S1.7 Slowly pour the crude CMC-CTS-Gal solution into 3 times its volume of ethanol solution while stirring. After it is completely mixed, let it stand for 25-35 minutes until no excess white precipitate is formed. S1.8 After filtration, collect the precipitate and wash it several times with ethanol solution until the washing solution tests negative with p-toluenesulfonic acid test paper. S1.

9. Dry the washed precipitate for 10-15 hours to constant weight, then pulverize and sieve to obtain the modified chitosan.

5. The method for preparing the compound feed for improving goose immunity according to claim 4, characterized in that: S2 specifically includes the following steps: S2.

1. Take sodium alginate powder, sieve it and dry it to obtain SA fine material. Take dextran powder, dissolve it in deionized water, filter it and concentrate it under reduced pressure to obtain GL concentrated solution. S2.2 Add the SA fines to deionized water and stir until the SA is completely dissolved and the solution viscosity is 300-400 mPa·s to obtain an SA solution; S2.

3. The GL concentrate is slowly added dropwise to the SA solution at a rate of 0.9-1.1 mL. After the addition is complete, the temperature is raised to 30°C and stirred for 2 hours to obtain the SA-GL composite solution. S2.4 Add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide to the SA-GL composite solution, and stir until the pH of the solution is 5.5-6.0 to obtain a mixed solution; S2.5 Dissolve propylene glycol alginate powder in deionized water, filter, and slowly add it dropwise to the mixture at a rate of 0.9-1.1 mL. After the addition is complete, seal the container and stir for 2.5-3.5 hours to obtain SA-GL-PGA crude solution. S2.6 Slowly pour the crude SA-GL-PGA solution into 4 times its volume of acetone while stirring. After it is completely mixed, let it stand for 15-25 minutes until no excess white precipitate is formed. S2.

7. Collect the precipitate by vacuum filtration, and wash it several times with acetone until the total residual amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide in the washing solution is <0.05 wt%. S2.

8. Dry the washed precipitate for 10-15 hours until constant weight, then pulverize and sieve to obtain the modified dextran.

6. The method for preparing the compound feed for improving goose immunity according to claim 3, characterized in that: The screen mesh size for the first sieve is 10-15 mesh, and the screen mesh size for the second sieve is 4-6 mesh.

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