Application of microalgae polysaccharide in improving intestinal immunity of dairy cow

Abstract

The invention relates to application of microalgae polysaccharide in improving intestinal immunity of dairy cows, belongs to the technical field of feeds, and the microalgae polysaccharide prepared by the invention is used for improving the secretion volume of intestinal mucosa to lgA, lgG and lgM. Kelp buds, dunaliella salina and haematococcus pluvialis are compounded and mixed according to a specific proportion, trypsin and nattokinase are adopted for pre-enzymolysis within a certain period of time, then hemicellulase and pectinase are adopted for enzymolysis within a certain period of time, and the enzymolysis effect is good. The obtained microalgae polysaccharide product has an excellent effect of promoting the intestinal tract of the dairy cow to secrete immune globulin, the content of IgA, IgG and IgM in the intestinal tract of the dairy cow can be greatly increased, the immunity of the intestinal tract of the dairy cow is further improved, and the microalgae polysaccharide product can be used as a substitute component for efficiently improving the immune function of the intestinal tract of the dairy cow.

Description

Technical Field

[0001] The invention belongs to the technical field of feed, and particularly relates to application of microalgae polysaccharide in improving intestinal immunity of dairy cows. Background Art

[0002] As people pay more and more attention to food safety and health, the dairy farming industry is also facing higher requirements. Improving the health level and production performance of dairy cows has become the key to the sustainable development of the dairy farming industry. The intestines of dairy cows are a complex ecosystem, inhabited by a large number of microorganisms. These microorganisms are closely related to the health of dairy cows. They can not only help dairy cows digest food and absorb nutrients, but also regulate the immune system of dairy cows. However, when the intestines of dairy cows are disturbed by external factors, such as feed changes, environmental stress, pathogen infection, etc., the balance of intestinal microbial communities may be broken, resulting in a decline in intestinal immune function, thereby causing various diseases.

[0003] In traditional dairy farming, antibiotics are often used to prevent and treat intestinal diseases in dairy cows. However, long-term use of antibiotics can lead to drug resistance in pathogens and also destroy the balance of intestinal microbial communities, affecting the health and production performance of dairy cows. Therefore, finding a safe and effective alternative method to improve the intestinal immune function of dairy cows has become an urgent need in the dairy farming industry.

[0004] Microalgae are a type of autotrophic organism that is widely distributed on land and in the ocean, rich in nutrients, and has a high photosynthetic utilization rate. Its cell metabolism chemical composition is complex, rich in proteins, lipids, algae polysaccharides, β-carotene, and a variety of inorganic elements. Due to its fast reproduction, high photosynthesis efficiency, short growth cycle, simple nutrients required (mainly sunlight, water and carbon dioxide), and no competition with agricultural and animal husbandry development, it can also use photosynthesis to capture carbon dioxide in exhaust gas and alleviate the greenhouse effect, so it has huge potential for social and economic benefits.

[0005] Among them, microalgae polysaccharides are generally acidic heteropolysaccharides, with complex monosaccharide composition and many sulfated modifications, glycosidic bonds in the connection mode, and many branches; the relative molecular mass is generally large, mostly greater than 10kDa. At present, the extraction of algae polysaccharides at home and abroad mainly adopts the method of dilute alkali, dilute acid and hot water extraction, which has the problems of low extraction rate, large activity loss and poor efficacy of active substances.

[0006] Therefore, it is necessary to continuously improve the biological ingredient extraction technology and develop safe and stable alternative ingredients to enhance the intestinal immune function of dairy cows. Summary of the invention

[0007] The existing hormone components for improving the intestinal immune function of dairy cows will destroy the balance of intestinal microbial communities and affect the health and production performance of dairy cows. The extraction of microalgae components has the problems of low extraction rate, large activity loss, poor efficacy of active substances, and the extract has the problem of unclear use effect, which makes it difficult to use as an alternative component for efficiently improving the intestinal immune function of dairy cows. The present invention provides an application of microalgae polysaccharides in improving the intestinal immunity of dairy cows. Kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are compounded and mixed in a specific proportion, and trypsin and nattokinase are used for pre-enzymatic hydrolysis within a certain period of time, and then hemicellulase and pectinase are used for enzymatic hydrolysis within a certain period of time. The obtained microalgae polysaccharide product has an excellent effect of promoting the secretion of immunoglobulins in the intestines of dairy cows, and can greatly increase the content of IgA, IgG and IgM in the intestines of dairy cows, thereby improving the immunity of the intestines of dairy cows, and can be used as an alternative component for efficiently improving the intestinal immune function of dairy cows. The specific technical scheme is as follows: The invention discloses an application of microalgae polysaccharide in improving intestinal immunity of dairy cows. The microalgae polysaccharide is used to increase the secretion of intestinal mucosa to IgA, IgG and IgM. The preparation method of the microalgae polysaccharide comprises the following steps: mixing and crushing the kelp buds, Dunaliella salina and Haematococcus pluvialis according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100: (6-10): (2-5) to obtain a slurry; adding saline solution 8 to 12 times the mass of the slurry to the slurry, adjusting the pH to 7.8 to 8.5, adding trypsin and nattokinase, performing enzymolysis at 36 to 42°C for 90 to 120 minutes, adjusting the pH to 5.0 to 5.5, adding hemicellulase and pectinase, performing enzymolysis at 45 to 55°C for 50 to 80 minutes, filtering with a sieve, taking the filtrate, and freeze-drying to obtain a microalgae polysaccharide product.

[0008] In the above technical solution, the kelp sprouts, Dunaliella salina and Haematococcus pluvialis are all freshly washed raw materials.

[0009] In the above technical solution, the concentration of the brine is 5wt% to 8wt%.

[0010] In the above technical solution, the amount of trypsin added is 0.2% to 0.5% of the mass of the slurry; the enzyme activity of trypsin is 2000U / g to 4000U / g.

[0011] In the above technical solution, the added amount of the nattokinase is 0.5% to 1.0% of the slurry mass; the enzyme activity of the nattokinase is 10,000 U / g to 50,000 U / g.

[0012] In the above technical solution, the added amount of the hemicellulase is 0.3% to 0.5% of the mass of the slurry; the enzyme activity of the hemicellulase is 50,000 U / g to 100,000 U / g.

[0013] In the above technical solution, the added amount of the pectinase is 0.8% to 1.2% of the slurry mass; the enzyme activity of the pectinase is 10,000 U / g to 30,000 U / g.

[0014] In the above technical solution, the mesh size of the sieve is 325 to 400 meshes.

[0015] In the above technical solution, the microalgae polysaccharide product also contains protein peptides.

[0016] In the above technical solution, the microalgae polysaccharide can increase the secretion of IgA, IgG and IgM in the intestinal mucosa of dairy cows by more than 30%.

[0017] The application of a microalgae polysaccharide provided by the present invention in improving intestinal immunity of dairy cows has the following beneficial effects compared with the prior art: 1. Different types of microalgae have very different monosaccharide components, such as glucose, galactose, mannose, arabinose, fucose, rhamnose, ribose and xylose, and other nutrients, which affect the specific use of the efficacy and effect. The present invention uses kelp sprouts, Dunaliella salina, and Haematococcus pluvialis to mix in a specific ratio, use trypsin and nattokinase to pre-enzyme for a certain period of time, and then use hemicellulase and pectinase to enzymolyze for a certain period of time. The obtained microalgae polysaccharide product has an excellent effect of promoting the secretion of immunoglobulins in the intestines of dairy cows, and can greatly increase the content of IgA, IgG and IgM in the intestines of dairy cows, thereby improving the immunity of the intestines of dairy cows.

[0018] 2. The microalgae polysaccharides prepared by the present invention also contain small molecule peptides and other small molecule water-soluble nutrients, which can act as a nonspecific immune activator to enhance the immune function of animals; they can activate macrophages and complement, promote antibody formation and induce interferon, etc., thereby enhancing the cellular immunity and humoral immunity of the animal body.

[0019] 3. The microalgae polysaccharide prepared by the present invention contains rich nutrients, which can provide energy and nutrients for animals, promote the growth and development of animals, and improve the growth performance indicators such as the weight growth rate and feed conversion rate of animals.

[0020] Fourth, the microalgae polysaccharide prepared by the present invention contains small molecule peptides, which can be used in combination with microalgae polysaccharides to regulate the intestinal flora of animals, increase the number of beneficial bacteria, inhibit the growth of harmful bacteria, and thus improve intestinal health. It promotes the repair and regeneration of intestinal mucosa, enhances the barrier function of the intestine, and reduces the occurrence of intestinal diseases.

[0021] 5. The microalgae polysaccharide product of the present invention has good adhesion and stability, can also improve the moldability and particle quality of feed, and reduce the loss of feed during processing and transportation. At the same time, it can also serve as a natural antioxidant to extend the shelf life of feed. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific implementation cases, but the present invention is not limited to these embodiments.

[0023] Example 1 A microalgae polysaccharide is used for improving the intestinal immunity of dairy cows. The microalgae polysaccharide is used for increasing the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0024] The preparation method of microalgae polysaccharides comprises the following steps: according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:8:3, freshly washed kelp buds, Dunaliella salina and Haematococcus pluvialis are mixed and crushed to obtain a slurry; saline solution with a concentration of 6wt% which is 10 times the mass of the slurry is added to the slurry, the pH value is adjusted to 8.0, 0.3% of trypsin and 0.8% of nattokinase are added to the slurry, enzymolysis is performed at 38°C for 100min, the pH value is adjusted to 5.2, 0.4% of hemicellulase and 1.0% of pectinase are added to the slurry, enzymolysis is performed at 50°C for 65min, filtering is performed using a 400-mesh sieve, taking the filtrate, and freeze-drying to obtain a microalgae polysaccharide product; the microalgae polysaccharide product also contains protein peptides.

[0025] The trypsin enzyme activity used in this embodiment is 3000 U / g; the enzyme activity of nattokinase is 30,000 U / g; the enzyme activity of hemicellulase is 80,000 U / g; and the enzyme activity of pectinase is 20,000 U / g.

[0026] Example 2 A microalgae polysaccharide is used for improving the intestinal immunity of dairy cows. The microalgae polysaccharide is used for increasing the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0027] The preparation method of microalgae polysaccharides comprises the following steps: according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:6:2, freshly washed kelp buds, Dunaliella salina and Haematococcus pluvialis are mixed and crushed to obtain a slurry; salt water with a concentration of 5wt% which is 8 times the mass of the slurry is added to the slurry, the pH value is adjusted to 7.8, 0.2% of trypsin and 0.5% of nattokinase are added to the slurry, enzymolysis is performed at 36°C for 90min, the pH value is adjusted to 5.0, 0.3% of hemicellulase and 0.8% of pectinase are added to the slurry, enzymolysis is performed at 45°C for 50min, filtering is performed using a 325-mesh sieve, taking the filtrate, and freeze-drying to obtain a microalgae polysaccharide product; the microalgae polysaccharide product also contains protein peptides.

[0028] The trypsin enzyme activity used in this embodiment is 2000 U / g; the enzyme activity of nattokinase is 10,000 U / g; the enzyme activity of hemicellulase is 50,000 U / g; and the enzyme activity of pectinase is 10,000 U / g.

[0029] Example 3 A microalgae polysaccharide is used for improving the intestinal immunity of dairy cows. The microalgae polysaccharide is used for increasing the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0030] The preparation method of microalgae polysaccharides comprises the following steps: according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:7:2.5, freshly washed kelp buds, Dunaliella salina and Haematococcus pluvialis are mixed and crushed to obtain a slurry; saline solution with a concentration of 5.5wt% which is 9 times the mass of the slurry is added to the slurry, the pH value is adjusted to 7.9, 0.3% of trypsin and 0.6% of nattokinase are added to the slurry, enzymolysis is performed at 37°C for 95min, the pH value is adjusted to 5.1, 0.4% of hemicellulase and 0.9% of pectinase are added to the slurry, enzymolysis is performed at 48°C for 60min, filtering is performed using a 325-mesh sieve, taking the filtrate, and freeze-drying to obtain a microalgae polysaccharide product; the microalgae polysaccharide product also contains protein peptides.

[0031] The trypsin enzyme activity used in this embodiment is 2000 U / g; the enzyme activity of nattokinase is 50,000 U / g; the enzyme activity of hemicellulase is 50,000 U / g; and the enzyme activity of pectinase is 30,000 U / g.

[0032] Example 4 A microalgae polysaccharide is used for improving the intestinal immunity of dairy cows. The microalgae polysaccharide is used for increasing the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0033] The preparation method of microalgae polysaccharides comprises the following steps: according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:10:5, freshly washed kelp buds, Dunaliella salina and Haematococcus pluvialis are mixed and crushed to obtain a slurry; 8wt% salt water with a concentration of 12 times the mass of the slurry is added to the slurry, the pH is adjusted to 8.5, 0.5% of trypsin by mass of the slurry and 1.0% of nattokinase by mass of the slurry are added, enzymolysis is performed at 42°C for 120min, the pH is adjusted to 5.5, 0.5% of hemicellulase by mass of the slurry and 1.2% of pectinase by mass of the slurry are added, enzymolysis is performed at 55°C for 80min, filtering is performed using a 400-mesh sieve, taking the filtrate, and freeze-drying to obtain a microalgae polysaccharide product; the microalgae polysaccharide product also contains protein peptides.

[0034] The trypsin enzyme activity used in this embodiment is 4000 U / g; the enzyme activity of nattokinase is 50,000 U / g; the enzyme activity of hemicellulase is 100,000 U / g; and the enzyme activity of pectinase is 30,000 U / g.

[0035] Example 5 A microalgae polysaccharide is used for improving the intestinal immunity of dairy cows. The microalgae polysaccharide is used for increasing the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0036] The preparation method of microalgae polysaccharides comprises the following steps: according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:9:4, freshly washed kelp buds, Dunaliella salina and Haematococcus pluvialis are mixed and crushed to obtain a slurry; saline solution with a concentration of 7wt% which is 11 times the mass of the slurry is added to the slurry, the pH is adjusted to 8.4, 0.3% of trypsin and 0.7% of nattokinase are added to the slurry, enzymolysis is performed at 40°C for 110min, the pH is adjusted to 5.3, 0.4% of hemicellulase and 1.1% of pectinase are added to the slurry, enzymolysis is performed at 52°C for 70min, filtering is performed using a 400-mesh sieve, taking the filtrate, and freeze-drying to obtain a microalgae polysaccharide product; the microalgae polysaccharide product also contains protein peptides.

[0037] The trypsin enzyme activity used in this embodiment is 4000 U / g; the enzyme activity of nattokinase is 10,000 U / g; the enzyme activity of hemicellulase is 100,000 U / g; and the enzyme activity of pectinase is 10,000 U / g.

[0038] Comparative Example 1 In the preparation method of microalgae polysaccharide, trypsin is not added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0039] Comparative Example 2 In the preparation method of microalgae polysaccharide, nattokinase is not added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0040] Comparative Example 3 In the preparation method of microalgae polysaccharide, trypsin and nattokinase are not added for enzymatic hydrolysis; that is, the slurry is directly hydrolyzed by hemicellulase and pectinase. Other methods and parameters are the same as those in Example 1.

[0041] Comparative Example 4 In the preparation method of microalgae polysaccharide, the enzymatic hydrolysis time of trypsin and nattokinase is 180 minutes, that is, the enzymatic hydrolysis time is too long. Other methods and parameters are the same as in Example 1.

[0042] Comparative Example 5 In the preparation method of microalgae polysaccharide, the enzymatic hydrolysis time of trypsin and nattokinase is 50 minutes, that is, the enzymatic hydrolysis time is too short. Other methods and parameters are the same as in Example 1.

[0043] Comparative Example 6 In the preparation method of microalgae polysaccharide, hemicellulase is not added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0044] Comparative Example 7 In the preparation method of microalgae polysaccharide, pectinase is not added for enzymolysis. Other methods and parameters are the same as in Example 1.

[0045] Comparative Example 8 In the preparation method of microalgae polysaccharide, hemicellulase and pectinase are not added for enzymatic hydrolysis at the same time; that is, the slurry is directly filtered after enzymatic hydrolysis by trypsin and nattokinase. Other methods and parameters are the same as those in Example 1.

[0046] Comparative Example 9 In the preparation method of microalgae polysaccharide, the enzymatic hydrolysis time of hemicellulase and pectinase is 120 minutes, that is, the enzymatic hydrolysis time is too long. Other methods and parameters are the same as in Example 1.

[0047] Comparative Example 10 In the preparation method of microalgae polysaccharide, the enzymatic hydrolysis time of hemicellulase and pectinase is 30 minutes, that is, the enzymatic hydrolysis time is too short. Other methods and parameters are the same as in Example 1.

[0048] The microalgae polysaccharides prepared in the above-mentioned embodiments and comparative examples were tested.

[0049] 1. Mouse toxicity experiment: The microalgae polysaccharides obtained in Examples 1 to 5 were used for mouse toxicity tests, and a negative control group was set up. Each group used 10 male weaned mice weighing 15g to 21g, which were raised in a constant temperature and humidity environment (temperature 25°C, humidity 45%), and 10 mg / g of microalgae polysaccharides were added to the diet. The mice were slaughtered after four weeks. The general condition of the mice was observed every week. At the end of the test, blood was collected from the eyeballs for routine blood tests. All mice were slaughtered to observe whether there were pathological changes in the internal organs, and the liver, kidney, and spleen of all animals were weighed. The results are shown in Table 1.

[0050] Table 1 Results of mouse toxicity test The products of Comparative Examples 1 to 10 tested in the same manner as above are also safe and non-toxic, and the test results are omitted.

[0051] From the above results, it can be seen that there is no significant difference in the effect of large doses of microalgae polysaccharides (10 mg / g) on ​​the general condition, weight of major organs and blood routine of mice, and it is believed that microalgae polysaccharides are basically non-toxic to mice.

[0052] 2. Test to enhance intestinal immunoglobulin secretion Basic feed formula: 45% corn, 15% bran, 25% soybean meal, 10% rapeseed meal, and 5% mineral and vitamin premix.

[0053] The feed formula containing microalgae polysaccharides: 3% microalgae polysaccharides (corresponding to the microalgae polysaccharides prepared in each embodiment and each comparative example), 45% corn, 12% bran, 25% soybean meal, 10% rapeseed meal, and 5% mineral and vitamin premix.

[0054] In a farm, 160 Holstein cows aged 2 to 5 were selected, and the ELISA kit was used to detect the content of immunoglobulins IgA, IgG and IgM in the initial feces (d0 value), and then divided into 16 groups, and continued to be raised in a well-ventilated environment, and the ambient temperature was controlled at 25±5℃; one group was a blank control group, which was fed normally with basic feed; the remaining 15 groups were experimental groups, which were fed with feed containing microalgae polysaccharides every day (each group corresponded to the feed containing microalgae polysaccharides of each embodiment and each comparative example); after continuous feeding for 15 days, the feces samples of the cows were collected, homogenized, and centrifuged after adding an appropriate amount of phosphate buffer (PBS), and the supernatant was taken, and the contents of IgA, IgG and IgM in the feces of the cows were determined by ELISA kits and microplate reader (d15 value). The test results are shown in Table 2 below.

[0055] Table 2 Results of immunoglobulin content determination in dairy cow feces (average value) From the above results, it can be seen that the IgA content in the cow feces of Examples 1 to 5 is increased by more than 80%, the IgG content is increased by more than 80%, and the IgM content is increased by more than 60%. Seaweed polysaccharides have a good effect of promoting the secretion of immunoglobulins in the intestines of cows, and effectively enhance intestinal immunity. From the results of Comparative Examples 1 to 3, it can be seen that in the preparation method of microalgae polysaccharides, trypsin or nattokinase is not added, so that the composition and content of the enzymatic hydrolysis small molecule peptide products are different, resulting in a decrease in the secretion rate of intestinal immunoglobulins; without trypsin and nattokinase enzymolysis, there is no rich small molecule peptide component, and the secretion content of intestinal immunoglobulins is greatly reduced, the secretion rate of IgA and IgG is less than 50%, and the secretion rate of IgM is less than 40%. From the results of Comparative Examples 4 and 5, it can be seen that if the enzymatic hydrolysis time of trypsin and nattokinase is too long or too short, it will affect the composition and content of small molecule peptides, and then affect the effect of promoting the secretion of intestinal immunoglobulins. From the results of Comparative Examples 6 and 8, it can be seen that without adding hemicellulase or pectinase, the extraction rate of microalgae polysaccharide components is reduced; hemicellulase and pectinase can hydrolyze macromolecular microalgae polysaccharides into smaller nutrients, which can better promote the secretion of immunoglobulins in the intestine. Without adding hemicellulase or pectinase, the composition of the product is affected, thereby reducing the effect; at the same time, without adding hemicellulase and pectinase, the effect of promoting the secretion of immunoglobulins in the intestine is greatly reduced, and the secretion increase rate of IgA and IgG is less than 40%, and the secretion increase rate of IgM is less than 30%. From the results of Comparative Examples 9 and 10, it can be seen that if the enzymatic hydrolysis time of hemicellulase and pectinase is too long or too short, it will affect the composition and content of microalgae polysaccharides, thereby affecting the effect of promoting the secretion of intestinal immunoglobulins.

Claims

1. An application of microalgae polysaccharide in improving intestinal immunity of dairy cows, characterized in that: Microalgae polysaccharides are used to increase the secretion of IgA, IgG and IgM by intestinal mucosa; the preparation method of the microalgae polysaccharides comprises the following steps: according to the mass ratio of kelp buds: Dunaliella salina: Haematococcus pluvialis = 100: (6-10): (2-5), kelp buds, Dunaliella salina and Haematococcus pluvialis are mixed and crushed to obtain a slurry; saline solution of 8 to 12 times the mass of the slurry is added to the slurry, the pH is adjusted to 7.8 to 8.5, trypsin and nattokinase are added, enzymolysis is performed at 36°C to 42°C for 90 minutes to 120 minutes, the pH is adjusted to 5.0 to 5.5, hemicellulase and pectinase are added, enzymolysis is performed at 45°C to 55°C for 50 minutes to 80 minutes, sieve filtering is used, the filtrate is taken, and freeze-drying is performed to obtain a microalgae polysaccharide product.

2. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The kelp sprouts, Dunaliella salina and Haematococcus pluvialis are all freshly washed raw materials.

3. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The concentration of the brine is 5wt% to 8wt%.

4. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The amount of trypsin added is 0.2% to 0.5% of the mass of the slurry; the enzyme activity of trypsin is 2000U / g to 4000U / g.

5. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The added amount of the nattokinase is 0.5% to 1.0% of the slurry mass; the enzyme activity of the nattokinase is 10,000 U / g to 50,000 U / g.

6. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The amount of hemicellulase added is 0.3% to 0.5% of the mass of the slurry; the enzyme activity of the hemicellulase is 50,000 U / g to 100,000 U / g.

7. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The added amount of the pectinase is 0.8% to 1.2% of the slurry mass; the enzyme activity of the pectinase is 10,000 U / g to 30,000 U / g.

8. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The mesh number of the sieve is 325-400 meshes.

9. The use of a microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The microalgae polysaccharide product also contains protein peptides.

10. The use of microalgae polysaccharide in improving intestinal immunity of dairy cows according to claim 1, characterized in that: The microalgae polysaccharide can increase the secretion of IgA, IgG and IgM in the intestinal mucosa of dairy cows by more than 30%.

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