Application of a microalgal polysaccharide in enhancing intestinal immunity in dairy cows

Abstract

This invention relates to the application of microalgae polysaccharides in enhancing intestinal immunity in dairy cows, belonging to the field of feed technology. The microalgae polysaccharides prepared by this invention are used to increase the secretion of IgA, IgG, and IgM by the intestinal mucosa. This invention uses a specific ratio of kelp buds, Dunaliella salina, and Haematococcus pluvialis for pre-enzymatic hydrolysis using trypsin and nattokinase for a certain period of time, followed by enzymatic hydrolysis using hemicellulase and pectinase for a certain period of time. The resulting microalgae polysaccharide product has excellent effects in promoting the secretion of immunoglobulins in the dairy cow intestine, significantly increasing the content of IgA, IgG, and IgM in the dairy cow intestine, thereby enhancing intestinal immunity. It can serve as a highly effective alternative component for improving the intestinal immune function of dairy cows.

Description

Technical Field

[0001] This invention belongs to the field of feed technology, specifically relating to the application of a microalgae polysaccharide in improving the intestinal immunity of dairy cows. Background Technology

[0002] With increasing public concern for food safety and health, the dairy farming industry faces higher demands. Improving the health and productivity of dairy cows has become crucial for the sustainable development of the industry. The dairy cow's gut is a complex ecosystem home to a vast number of microorganisms. These microorganisms are closely related to the cow's health, not only helping them digest food and absorb nutrients but also regulating their immune system. However, when the dairy cow's gut is disturbed by external factors, such as changes in feed, environmental stress, or pathogen infection, the balance of the gut microbiota can be disrupted, leading to a decline in intestinal immune function and thus triggering various diseases.

[0003] In traditional dairy farming, antibiotics are commonly used to prevent and treat intestinal diseases in dairy cows. However, long-term use of antibiotics can lead to antibiotic resistance in pathogens and disrupt the balance of the gut microbiota, affecting the health and productivity of dairy cows. Therefore, finding a safe and effective alternative 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 widely distributed on land and in the ocean, rich in nutrients, and with high photosynthetic efficiency. Their cellular metabolism has a complex chemical composition, rich in proteins, lipids, algal polysaccharides, β-carotene, and various inorganic elements. Due to their rapid reproduction, high photosynthetic efficiency, short growth cycle, simple nutrient requirements (mainly sunlight, water, and carbon dioxide), and the fact that they do not compete with agricultural and pastoral development for land, and can also capture carbon dioxide from waste gases through photosynthesis to mitigate the greenhouse effect, they possess enormous potential for socio-economic benefits.

[0005] Microalgal polysaccharides are generally acidic heteropolysaccharides with complex monosaccharide compositions, often modified by sulfation, and linked by glycosidic bonds, often exhibiting branching. Their relative molecular mass is generally large, often exceeding 10 kDa. Currently, the main methods for extracting algal polysaccharides both domestically and internationally are dilute alkali, dilute acid, and hot water extraction, which suffer from low extraction rates, significant loss of activity, and poor efficacy of active substances.

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

[0007] Existing hormonal components used to enhance intestinal immune function in dairy cows can disrupt the balance of the intestinal microbiota, affecting the health and production performance of dairy cows. Microalgae extraction suffers from low extraction rates, significant loss of activity, poor efficacy of active substances, and insignificant effects, making it difficult to serve as a highly effective alternative for enhancing intestinal immune function in dairy cows. This invention provides an application of microalgae polysaccharides in enhancing intestinal immunity in dairy cows. A specific ratio of kelp sprouts, Dunaliella salina, and Haematococcus pluvialis is used for pre-enzymatic hydrolysis with trypsin and nattokinase within a certain time, followed by enzymatic hydrolysis with hemicellulase and pectinase within a certain time. The resulting microalgae polysaccharide product exhibits excellent effects in promoting the secretion of immunoglobulins in the dairy cow intestine, significantly increasing the levels of IgA, IgG, and IgM in the dairy cow intestine, thereby enhancing intestinal immunity and serving as a highly effective alternative for enhancing intestinal immune function in dairy cows. The specific technical solution is as follows:

[0008] An application of a microalgal polysaccharide in improving intestinal immunity in dairy cows, wherein the microalgal polysaccharide is used to increase the secretion of IgA, IgG and IgM by the intestinal mucosa; the preparation method of the microalgal polysaccharide includes the following steps: Kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:(6-10):(2-5) by mass ratio; Kelp buds, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 8-12 times the mass of the slurry is added to the slurry, the pH is adjusted to 7.8-8.5, trypsin and nattokinase are added, and enzymatic hydrolysis is carried out at 36℃-42℃ for 90-120 min; the pH is adjusted to 5.0-5.5, hemicellulase and pectinase are added, and enzymatic hydrolysis is carried out at 45℃-55℃ for 50-80 min; the mixture is filtered through a sieve, the filtrate is collected, and freeze-dried to obtain the microalgal polysaccharide product.

[0009] In the above technical solution, the kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are all fresh and cleaned raw materials.

[0010] In the above technical solution, the concentration of the brine is 5wt% to 8wt%.

[0011] 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 2000 U / g to 4000 U / g.

[0012] In the above technical solution, the amount of nattokinase added is 0.5% to 1.0% of the slurry mass; the enzyme activity of nattokinase is 10,000 U / g to 50,000 U / g.

[0013] In the above technical solution, the amount of hemicellulase added is 0.3% to 0.5% of the slurry mass; the enzyme activity of the hemicellulase is 50,000 U / g to 100,000 U / g.

[0014] In the above technical solution, the amount of pectinase added 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.

[0015] In the above technical solution, the mesh size of the sieve is 325 to 400 mesh.

[0016] In the above technical solution, the microalgal polysaccharide product also contains protein peptides.

[0017] 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%.

[0018] The application of a microalgal polysaccharide provided by this invention in improving intestinal immunity in dairy cows has the following advantages compared with existing technologies:

[0019] I. Different types of microalgae have vastly different monosaccharide compositions, including variations in the content and amount of glucose, galactose, mannose, arabinose, fucose, rhamnose, ribose, and xylose, as well as other nutrients. These differences affect the specific efficacy and degree of effectiveness of their applications. This invention uses a specific ratio of kelp sprouts, Dunaliella salina, and Haematococcus pluvialis for pre-enzymatic hydrolysis using trypsin and nattokinase within a certain timeframe, followed by further enzymatic hydrolysis using hemicellulase and pectinase within the same timeframe. The resulting microalgal polysaccharide product exhibits excellent effects in promoting the secretion of immunoglobulins in the dairy cow's intestines, significantly increasing the levels of IgA, IgG, and IgM, thereby enhancing the cow's intestinal immunity.

[0020] Second, the microalgal polysaccharides prepared in this invention also contain small molecule peptides and other small molecule water-soluble nutrients, which can act as a non-specific immune activator to enhance the immune function of animals; they can activate macrophages and complement, promote antibody formation and induce interferon, thereby enhancing the cellular and humoral immune functions of the animal body.

[0021] Third, the microalgae polysaccharides prepared by this invention contain abundant nutrients, which can provide energy and nutrients for animals, promoting their growth and development. This improves growth performance indicators such as weight gain rate and feed conversion ratio.

[0022] IV. The microalgae polysaccharide prepared in this invention contains small molecule peptides. When used in combination with the microalgae polysaccharide, it can 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 the intestinal mucosa, enhances the intestinal barrier function, and reduces the occurrence of intestinal diseases.

[0023] V. The microalgae polysaccharide product of this invention has good binding and stability, and can also improve the formability and pellet quality of feed, reducing feed loss during processing and transportation. Simultaneously, it can also act as a natural antioxidant, extending the shelf life of feed. Detailed Implementation

[0024] The present invention will be further described below with reference to specific implementation examples, but the present invention is not limited to these embodiments.

[0025] Example 1

[0026] An application of a microalgal polysaccharide in enhancing intestinal immunity in dairy cows, wherein the microalgal polysaccharide is used to increase the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0027] The preparation method of microalgal polysaccharide includes the following steps: Kelp sprouts: Dunaliella salina: Haematococcus pluvialis = 100:8:3 by mass ratio; freshly washed kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 10 times the slurry mass of 6wt% saline solution is added to the slurry to adjust the pH to 8.0; 0.3% of the slurry mass of trypsin and 0.8% of the slurry mass of nattokinase are added, and enzymatic hydrolysis is carried out at 38℃ for 100 min; the pH is adjusted to 5.2; 0.4% of the slurry mass of hemicellulase and 1.0% of the slurry mass of pectinase are added, and enzymatic hydrolysis is carried out at 50℃ for 65 min; the mixture is filtered through a 400-mesh sieve, and the filtrate is collected and freeze-dried to obtain the microalgal polysaccharide product; the microalgal polysaccharide product also contains protein peptides.

[0028] In this embodiment, the enzyme activity of trypsin was 3000 U / g; the enzyme activity of nattokinase was 30,000 U / g; the enzyme activity of hemicellulase was 80,000 U / g; and the enzyme activity of pectinase was 20,000 U / g.

[0029] Example 2

[0030] An application of a microalgal polysaccharide in enhancing intestinal immunity in dairy cows, wherein the microalgal polysaccharide is used to increase the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0031] The preparation method of microalgal polysaccharide includes the following steps: Kelp sprouts: Dunaliella salina: Haematococcus pluvialis = 100:6:2 by mass ratio; freshly washed kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 8 times the slurry mass of 5wt% saline solution is added to the slurry to adjust the pH to 7.8; 0.2% of the slurry mass of trypsin and 0.5% of the slurry mass of nattokinase are added, and enzymatic hydrolysis is carried out at 36℃ for 90 min; the pH is adjusted to 5.0; 0.3% of the slurry mass of hemicellulase and 0.8% of the slurry mass of pectinase are added, and enzymatic hydrolysis is carried out at 45℃ for 50 min; the mixture is filtered through a 325-mesh sieve, and the filtrate is collected and freeze-dried to obtain the microalgal polysaccharide product; the microalgal polysaccharide product also contains protein peptides.

[0032] In this embodiment, the enzyme activity of trypsin was 2000 U / g; the enzyme activity of nattokinase was 10,000 U / g; the enzyme activity of hemicellulase was 50,000 U / g; and the enzyme activity of pectinase was 10,000 U / g.

[0033] Example 3

[0034] An application of a microalgal polysaccharide in enhancing intestinal immunity in dairy cows, wherein the microalgal polysaccharide is used to increase the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0035] The preparation method of microalgal polysaccharide includes the following steps: Kelp sprouts: Dunaliella salina: Haematococcus pluvialis = 100:7:2.5 by mass ratio; freshly washed kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 9 times the slurry mass of 5.5wt% saline solution is added to the slurry to adjust the pH to 7.9; 0.3% of the slurry mass of trypsin and 0.6% of the slurry mass of nattokinase are added, and enzymatic hydrolysis is carried out at 37℃ for 95 min; the pH is adjusted to 5.1; 0.4% of the slurry mass of hemicellulase and 0.9% of the slurry mass of pectinase are added, and enzymatic hydrolysis is carried out at 48℃ for 60 min; the mixture is filtered through a 325-mesh sieve, and the filtrate is collected and freeze-dried to obtain the microalgal polysaccharide product; the microalgal polysaccharide product also contains protein peptides.

[0036] In this embodiment, the enzyme activity of trypsin was 2000 U / g; the enzyme activity of nattokinase was 50,000 U / g; the enzyme activity of hemicellulase was 50,000 U / g; and the enzyme activity of pectinase was 30,000 U / g.

[0037] Example 4

[0038] An application of a microalgal polysaccharide in enhancing intestinal immunity in dairy cows, wherein the microalgal polysaccharide is used to increase the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0039] The preparation method of microalgal polysaccharide includes the following steps: Kelp sprouts: Dunaliella salina: Haematococcus pluvialis = 100:10:5 by mass ratio; freshly washed kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 8wt% brine (12 times the slurry mass) is added to the slurry to adjust the pH to 8.5; 0.5% trypsin and 1.0% nattokinase (by slurry mass) are added; enzymatic hydrolysis is carried out at 42℃ for 120 min; the pH is adjusted to 5.5; 0.5% hemicellulase and 1.2% pectinase (by slurry mass) are added; enzymatic hydrolysis is carried out at 55℃ for 80 min; the mixture is filtered through a 400-mesh sieve; the filtrate is collected and freeze-dried to obtain the microalgal polysaccharide product; the microalgal polysaccharide product also contains protein peptides.

[0040] In this embodiment, the enzyme activity of trypsin was 4000 U / g; the enzyme activity of nattokinase was 50,000 U / g; the enzyme activity of hemicellulase was 100,000 U / g; and the enzyme activity of pectinase was 30,000 U / g.

[0041] Example 5

[0042] An application of a microalgal polysaccharide in enhancing intestinal immunity in dairy cows, wherein the microalgal polysaccharide is used to increase the secretion of IgA, IgG and IgM by the intestinal mucosa.

[0043] The preparation method of microalgal polysaccharide includes the following steps: Kelp sprouts: Dunaliella salina: Haematococcus pluvialis = 100:9:4 by mass ratio; freshly washed kelp sprouts, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 11 times the slurry mass of 7wt% saline solution is added to the slurry to adjust the pH to 8.4; 0.3% of the slurry mass of trypsin and 0.7% of the slurry mass of nattokinase are added, and enzymatic hydrolysis is carried out at 40℃ for 110 min; the pH is adjusted to 5.3; 0.4% of the slurry mass of hemicellulase and 1.1% of the slurry mass of pectinase are added, and enzymatic hydrolysis is carried out at 52℃ for 70 min; the mixture is filtered through a 400-mesh sieve, and the filtrate is freeze-dried to obtain the microalgal polysaccharide product; the microalgal polysaccharide product also contains protein peptides.

[0044] In this embodiment, the enzyme activity of trypsin was 4000 U / g; the enzyme activity of nattokinase was 10,000 U / g; the enzyme activity of hemicellulase was 100,000 U / g; and the enzyme activity of pectinase was 10,000 U / g.

[0045] Comparative Example 1

[0046] In the preparation method of microalgal polysaccharides, trypsin is not added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0047] Comparative Example 2

[0048] In the preparation method of microalgal polysaccharides, nattokinase is not added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0049] Comparative Example 3

[0050] In the preparation method of microalgal polysaccharides, 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 in Example 1.

[0051] Comparative Example 4

[0052] In the preparation method of microalgal polysaccharides, the enzymatic hydrolysis time of trypsin and nattokinase was 180 min, which is too long. Other methods and parameters are the same as in Example 1.

[0053] Comparative Example 5

[0054] In the preparation method of microalgal polysaccharides, the enzymatic hydrolysis time of trypsin and nattokinase was 50 min, which is too short. Other methods and parameters are the same as in Example 1.

[0055] Comparative Example 6

[0056] In the preparation method of microalgal polysaccharides, no hemicellulase is added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0057] Comparative Example 7

[0058] In the preparation method of microalgal polysaccharides, no pectinase is added for enzymatic hydrolysis. Other methods and parameters are the same as in Example 1.

[0059] Comparative Example 8

[0060] In the preparation method of microalgal polysaccharides, hemicellulase and pectinase are not added for enzymatic hydrolysis; that is, the slurry is directly filtered after enzymatic hydrolysis with trypsin and nattokinase. Other methods and parameters are the same as in Example 1.

[0061] Comparative Example 9

[0062] In the preparation method of microalgal polysaccharides, the enzymatic hydrolysis time of hemicellulase and pectinase was 120 min, which is too long. Other methods and parameters are the same as in Example 1.

[0063] Comparative Example 10

[0064] In the preparation method of microalgal polysaccharides, the enzymatic hydrolysis time of hemicellulase and pectinase is 30 min, which is too short. Other methods and parameters are the same as in Example 1.

[0065] The microalgal polysaccharides prepared in the above embodiments and comparative examples were tested and evaluated.

[0066] I. Mouse toxicity test:

[0067] The microalgae polysaccharides obtained in Examples 1 to 5 were used in mouse toxicity tests, with a negative control group included. Each group consisted of 10 male weaned mice weighing 15g–21g, housed in a constant temperature and humidity environment (25℃, 45% humidity). 10mg / g of microalgae polysaccharides was added to their daily diet. Mice were slaughtered after four weeks. The general condition of the mice was observed weekly. At the end of the experiment, blood was collected from the iris for routine blood tests. All mice were slaughtered and their internal organs were examined for pathological changes. The liver, kidneys, and spleen of all animals were weighed. The results are shown in Table 1.

[0068] Table 1 Results of mouse toxicity assay

[0069]

[0070] The products obtained by testing Comparative Examples 1 to 10 using the same method described above were also safe and non-toxic; the test results are omitted.

[0071] The results above indicate that a high dose of microalgae polysaccharide (10 mg / g) had no significant effect on the general condition, weight of major organs, and blood routine of mice, suggesting that microalgae polysaccharide is essentially non-toxic to mice.

[0072] II. Tests to Enhance Intestinal Immunoglobulin Secretion

[0073] Basic feed formula: 45% corn, 15% wheat bran, 25% soybean meal, 10% rapeseed meal, and 5% mineral and vitamin premix.

[0074] Feed formulation containing microalgae polysaccharides: 3% microalgae polysaccharides (prepared using the microalgae polysaccharides of each example and each comparative example), 45% corn, 12% wheat bran, 25% soybean meal, 10% rapeseed meal, and 5% mineral and vitamin premix.

[0075] In a dairy farm, 160 Holstein dairy cows aged 2 to 5 years were selected. The initial fecal levels of immunoglobulins IgA, IgG, and IgM (d0 value) were detected using an ELISA kit. The cows were then divided into 16 groups and continued to be raised in a well-ventilated environment at a temperature controlled at 25±5℃. One group served as a blank control group, fed a normal basal diet. The remaining 15 groups were experimental groups, fed daily with feed containing microalgae polysaccharides (each group used feeds containing microalgae polysaccharides from the respective examples and comparative examples). After 15 days of continuous feeding, fecal samples were collected, homogenized, and centrifuged after adding an appropriate amount of phosphate-buffered saline (PBS). The supernatant was then used to determine the levels of IgA, IgG, and IgM in the feces using an ELISA kit and a microplate reader (d15 value). The results are shown in Table 2 below.

[0076] Table 2. Results of immunoglobulin content determination in dairy cow feces (average value)

[0077]

[0078] The results above show that the IgA content in the cow feces of Examples 1 to 5 increased by more than 80%, the IgG content increased by more than 80%, and the IgM content increased by more than 60%. Algae polysaccharides have a good effect on promoting the secretion of intestinal immunoglobulins in cows, effectively enhancing intestinal immunity. The results of Comparative Examples 1 to 3 show that in the preparation method of microalgae polysaccharides, the absence of trypsin or nattokinase resulted in different compositions and contents of the enzymatically hydrolyzed small molecule peptides, leading to a decrease in the rate of promoting intestinal immunoglobulin secretion. Without trypsin and nattokinase hydrolysis, there were no abundant small molecule peptide components, resulting in a significant decrease in the content of intestinal immunoglobulins secreted; the increase rate of IgA and IgG secretion was less than 50%, and the increase rate of IgM secretion was less than 40%. The results of Comparative Examples 4 and 5 show that both excessively long and short hydrolysis times of trypsin and nattokinase affect the composition and content of small molecule peptides, thus reducing the effect of promoting intestinal immunoglobulin secretion. The results of Comparative Examples 6 and 8 show that the absence of hemicellulase or pectinase reduces the extraction rate of microalgal polysaccharides. Hemicellulase and pectinase can enzymatically hydrolyze large-molecule microalgal polysaccharides into smaller nutrients, which can better promote the secretion of immunoglobulins in the intestine. The absence of hemicellulase or pectinase affects the composition of the product, thus reducing its effectiveness. Furthermore, the absence of hemicellulase and pectinase significantly reduces the effect of promoting the secretion of immunoglobulins in the intestine, with the increase rate of IgA and IgG secretion less than 40% and the increase rate of IgM secretion less than 30%. The results of Comparative Examples 9 and 10 show that both excessively long and short enzymatic hydrolysis times of hemicellulase and pectinase affect the composition and content of microalgal polysaccharides, thereby reducing the effect of promoting the secretion of immunoglobulins in the intestine.

Claims

1. The application of a microalgal polysaccharide in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, Microalgal polysaccharides are used to increase the secretion of IgA, IgG, and IgM by the intestinal mucosa. The preparation method of the microalgal polysaccharides includes the following steps: Kelp buds: Dunaliella salina: Haematococcus pluvialis = 100:(6-10):(2-5) by mass ratio; Kelp buds, Dunaliella salina, and Haematococcus pluvialis are mixed and pulverized to obtain a slurry; 8-12 times the mass of the slurry is added to the slurry to adjust the pH to 7.8-8.5; 0.2%-0.5% of the slurry mass of trypsin and 0.5% of the slurry mass of... ~1.0% nattokinase was used for enzymatic hydrolysis at 36℃~42℃ for 90min~120min. The pH was adjusted to 5.0~5.

5. Then, 0.3%~0.5% hemicellulase and 0.8%~1.2% pectinase by weight of the slurry were added, and the mixture was enzymatically hydrolyzed at 45℃~55℃ for 50min~80min. The mixture was filtered through a sieve, and the filtrate was freeze-dried to obtain a microalgal polysaccharide product containing protein peptides. The microalgal polysaccharide can increase the secretion of IgA, IgG and IgM in the intestinal mucosa of dairy cows by more than 30%.

2. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The kelp sprouts, Dunaliella salina, and Haematococcus pluvialis mentioned are all fresh and cleaned raw materials.

3. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The concentration of the brine is 5 wt% to 8 wt%.

4. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The enzyme activity of trypsin is 2000 U / g to 4000 U / g.

5. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The enzyme activity of the nattokinase is 10,000 U / g to 50,000 U / g.

6. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The enzyme activity of the hemicellulase is 50,000 U / g to 100,000 U / g.

7. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The pectinase activity is 10,000 U / g to 30,000 U / g.

8. The application of the microalgal polysaccharide according to claim 1 in the preparation of feed to improve intestinal immunity in dairy cows, characterized in that, The mesh size of the sieve is 325 to 400 mesh.

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