Preparation method and application of a kind of time-release silybin

Abstract

The application provides a preparation method and application of a post-rumen shikonin, and belongs to the technical field of biological medicine preparations. The post-rumen shikonin is prepared by adopting a core preparation and double-layer coating post-rumen process. In the core preparation, the addition of a flow aid can solve the problems of poor flowability and easy moisture absorption of the shikonin powder. The first layer of coating forms a functional isolation layer, which can preliminarily isolate the rumen environment and lay a good foundation for the second layer of coating. The second layer of coating is a post-rumen protective layer, which can form a solid physical barrier in the rumen.

Description

Technical Field

[0001] This invention belongs to the field of biopharmaceutical preparation technology, specifically relating to a method for preparing rumen-exposed silymarin and its application. Background Technology

[0002] Silymarin is a flavonoid compound (the core active ingredient of silymarin) extracted from the silymarin plant (Silybum marianum). Current research has confirmed its antioxidant, anti-inflammatory, hepatocyte membrane stabilizing, and hepatocyte repair promoting effects. Clinically, it is often used to assist in the improvement of specific liver diseases. The structure of silymarin is shown in formula (1): (1) Numerous studies have revealed that silymarin has strong effects on promoting production, enhancing liver antioxidant capacity, and protecting liver physiological function in livestock. Current animal production prioritizes high feed conversion rates, high productivity, and high energy metabolism, placing a significant burden on animal livers. Therefore, silymarin can be used as a feed additive in livestock farming to improve liver health and productivity. However, due to significant differences in the physiological metabolism of the digestive systems of different livestock, the low digestibility and absorption efficiency of silymarin needs to be addressed. In ruminants, due to the presence of the rumen, silymarin is first broken down by rumen microorganisms after ingestion, and high doses of silymarin can also negatively impact rumen microorganisms. Therefore, to improve the digestibility and absorption efficiency of silymarin in ruminants, a rumen-passing process is needed to treat silymarin, thereby increasing the rumen pass-through rate and small intestinal digestibility, maximizing the biological functions of silymarin without affecting normal rumen fermentation in ruminants. Summary of the Invention

[0003] Based on this, the present invention provides a method for preparing rumen-passing silybin, which adopts a core preparation and double-layer coating process to prepare rumen-passing silybin, and the silybin content in the rumen-passing silybin sample is 70-80%.

[0004] The present invention discloses a method for preparing rumen-protected silymarin, comprising the following steps: (1) Core processing: Silymarin powder is thoroughly mixed with a flow aid, then a binder solution is sprayed onto the mixed powder, wet granulation is used to make a soft material, which is then extruded through a screen, rolled into microspheres, and then dried to obtain the core. (2) First layer of coating: A coating solution is prepared by mixing oil, emulsifier, silymarin absorbent and water; the coating solution is then uniformly sprayed onto the core surface to complete the first coating layer. (3) Second layer of coating Solid oil, polyacrylic acid resin, anhydrous ethanol and excipients are mixed to obtain a dispersion; the dispersion is used as a coating agent for a second coating to obtain rumen-protected silymarin.

[0005] Preferably, the gliding agent in step (1) is magnesium stearate; the adhesive solution is a hydroxypropyl methylcellulose solution with a mass concentration of 1%-3%; and the gliding agent is 0.5%-1% of the mass of silymarin powder. The flow aid can solve the problems of poor flowability and easy moisture absorption of silymarin powder.

[0006] Preferably, the moisture content of the soft material in step (1) is 20-25%; the aperture of the sieve is 0.8-1.0 mm; and the particle size of the microspheres is 0.3-0.8 mm.

[0007] Preferably, the drying temperature in step (1) is 40-50°C and the time is 30-60 minutes, and the moisture content of the microspheres after drying is less than 3%.

[0008] Preferably, the oil in step (2) is hydrogenated palm oil, the emulsifier is glyceryl monostearate, and the silymarin absorption aid is hydroxypropyl-β-cyclodextrin.

[0009] The coating solution in step (2) comprises, by weight percentage, 7% to 18% oil, 1% to 4% emulsifier, 1% to 1.5% silymarin absorbent and the remainder water, with the sum of the weight percentages of each component being 100%.

[0010] Preferably, the spraying in step (2) is carried out using a bottom spray fluidized bed coating machine with an inlet temperature of 30-60℃; the first layer of coating has a mass of 15%-30% of the core weight.

[0011] Preferably, the solid oil in step (3) is at least one of palmitic acid and hydrogenated oil; the particle size of the polyacrylic acid resin is <80μm, the polyacrylic acid resin is polyacrylic acid resin III, and the excipients are one or more of zinc stearate, magnesium stearate, calcium oxide, talc, polyethylene glycol, glyceryl monostearate, glyceryl distearate, and triethyl citrate. Preferably, the solid oil is a mixture of palmitic acid and hydrogenated oil, and when the solid oil is a mixture of palmitic acid and hydrogenated oil, the mass ratio of palmitic acid to hydrogenated oil is 1.4:1.

[0012] Preferably, the mass ratio of the solid oil, polyacrylic acid resin, anhydrous ethanol and excipients in step (3) is 60-65:25-30:25-30:4-5.

[0013] Preferably, the second coating in step (3) is carried out using a bottom-spray fluidized bed with an air inlet temperature of 50-70°C and a material temperature of 40-50°C. The coating weight gain is 30%-50% of the core weight.

[0014] Another object of the present invention is to provide the application of the rumen-protected silymarin in dairy cow feeding.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing silybin through the rumen and its application. It adopts a rumen-passing process of core preparation and double-layer coating. Adding a flow aid in the core preparation can solve the problems of poor flowability and easy moisture absorption of silybin powder.

[0016] This invention achieves rumen protection of silybin through a double-layer coating. The first coating layer contains an oil (hydrogenated palm oil) that forms a hydrophobic barrier, while an emulsifier (glyceryl monostearate) improves the dispersibility of the coating solution and the uniformity of the film. A silybin absorption aid (hydroxypropyl-β-cyclodextrin) helps improve the dispersion and release of silybin in subsequent digestive fluids. The second coating layer contains solid oils (palmitic acid and hydrogenated oil) that form a dense lipid barrier, while polyacrylic acid resin III enhances the continuity, mechanical strength, and abrasion resistance of the film. Various excipients further improve the anti-sticking properties, flexibility, and stability of the coating layer.

[0017] In this invention, the first coating layer initially blocks rumen fluid from contacting the core and provides a smooth and stable substrate for the second coating layer to adhere. The second coating layer further enhances the barrier properties and structural stability of the formulation in the rumen. The synergistic effect of the two coating layers reduces the premature release and degradation of silymarin in the rumen and allows it to be gradually released after entering the subsequent digestive tract, thereby increasing the rumen clearance rate and small intestinal release rate of silymarin. Attached Figure Description

[0018] Figure 1 It is the silymarin standard curve; Figure 2 The results show the effect of rumen-passed silymarin on the body condition scores of lactating cows before and after calving. Detailed Implementation

[0019] This invention provides a method for preparing rumen-protected silymarin, comprising the following steps: (1) Core processing: Silymarin powder is thoroughly mixed with a flow aid, then a binder solution is sprayed onto the mixed powder, wet granulation is used to make a soft material, which is then extruded through a screen, rolled into microspheres, and then dried to obtain the core. (2) First layer of coating: A coating solution is prepared by mixing oil, emulsifier, silymarin absorbent and water; the coating solution is then uniformly sprayed onto the core surface to complete the first coating layer. (3) Second layer of coating Solid oil, polyacrylic acid resin, anhydrous ethanol and excipients are mixed to obtain a dispersion; the dispersion is used as a coating agent for a second coating to obtain rumen-protected silymarin.

[0020] Preferably, the gliding agent in step (1) is magnesium stearate; the adhesive solution is a hydroxypropyl methylcellulose (HPMC) solution with a mass concentration of 1%-3%; and the gliding agent is 0.5%-1% of the mass of silymarin powder. The flow aid can solve the problems of poor flowability and easy moisture absorption of silymarin powder.

[0021] Preferably, the moisture content of the soft material in step (1) is 25%; the aperture of the sieve is 0.8-1.0 mm; and the particle size of the microspheres is 0.3-0.8 mm.

[0022] Preferably, the drying temperature in step (1) is 40-50°C and the time is 30-60 minutes, and the moisture content of the microspheres after drying is less than 3%.

[0023] In a specific embodiment of the present invention, the core processing method is as follows: silymarin powder is thoroughly mixed with a flow aid, and wet granulation is performed. A binder solution is sprayed onto the mixed powder to produce a soft material with a water content of 25%. The soft material is extruded through a sieve with a pore size of 0.8-1.0 mm, and then sphericalized in a shot blasting machine to form smooth, dense spherical or near-spherical microspheres (particle size approximately 0.3-0.8 mm). The microspheres are then dried in a fluidized bed at 40-50°C for 30-60 minutes to reduce the water content of the microspheres to below 3%.

[0024] Preferably, the oil in step (2) is hydrogenated palm oil, the emulsifier is glyceryl monostearate, and the silymarin absorption aid is hydroxypropyl-β-cyclodextrin.

[0025] The coating solution in step (2) comprises, by weight percentage, 7%–18% hydrogenated palm oil, 1%–4% glyceryl monostearate, 1%–1.5% hydroxypropyl-β-cyclodextrin, and the balance water, with the sum of the weight percentages of each component being 100%.

[0026] Preferably, the spraying in step (2) is carried out using a bottom spray fluidized bed coating machine with an inlet temperature of 30-60℃; the first layer of coating has a mass of 15%-30% of the core weight.

[0027] In a specific embodiment of the present invention, the method for the first coating layer is as follows: hydrogenated palm oil is heated to 60-70°C to completely melt it, glyceryl monostearate is added and stirred evenly; hydroxypropyl-β-cyclodextrin is added to water and stirred to dissolve or evenly disperse at 50°C to obtain an aqueous phase; the aqueous phase is then slowly added to the molten oil phase and sheared at high speed at 50°C for 5-15 minutes to form a uniform water-in-oil (W / O) emulsion. Using a bottom-spray fluidized bed coating machine with the inlet temperature controlled at 30-60°C, the above emulsion is evenly sprayed onto the core surface, and this coating layer increases the weight by 15%-30% of the core weight.

[0028] Preferably, the solid oil in step (3) is at least one of palmitic acid and hydrogenated oil; the polyacrylic acid resin is polyacrylic acid resin III; and the excipients are one or more of zinc stearate, magnesium stearate, calcium oxide, talc, polyethylene glycol, glyceryl monostearate, glyceryl distearate, and triethyl citrate. Preferably, the solid oil is a mixture of palmitic acid and hydrogenated oil, and when the solid oil is a mixture of palmitic acid and hydrogenated oil, the mass ratio of palmitic acid to hydrogenated oil is 1.4:1.

[0029] Preferably, the mass ratio of the solid oil, polyacrylic acid resin, anhydrous ethanol and excipients in step (3) is 60-65:25-30:25-30:4-5.

[0030] Preferably, the second coating in step (3) is carried out using a bottom-spray fluidized bed with an air inlet temperature of 50-70°C and a material temperature of 40-50°C. The coating weight gain is 30%-50% of the core weight.

[0031] In a specific embodiment of the present invention, the second coating method is as follows: First, polyacrylic acid resin III with a particle size <80μm is mixed with a small amount of anhydrous ethanol, allowing it to fully absorb the ethanol and swell to form a polyacrylic acid resin III swollen material. Separately, solid oil is added to a mixing container, heated to 65-75°C, and continuously stirred until completely melted. Fusible or liquid excipients are added and mixed evenly. Then, the polyacrylic acid resin III swollen material is slowly added to the molten solid oil, and stirring is continued at 65-75°C for 10-20 minutes. Powdered excipients are then added in batches, and stirring is continued for 10-15 minutes to obtain a uniform oil-phase polyacrylic acid resin III dispersion. A bottom-spray fluidized bed is then used, with an inlet air temperature of 50-70°C and the material temperature maintained at 40-50°C. The coating weight gain target is 30%-50% of the core weight.

[0032] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0033] Example 1 A method for preparing rumen-protected silymarin, comprising the following steps: (1) Core processing: Silymarin powder is thoroughly mixed with magnesium stearate (0.75% of the mass of silymarin powder), and then HPMC solution (2% concentration) is sprayed into the mixed powder. Wet granulation is used to produce a soft material with a moisture content of 25%. The material is then extruded through a sieve with a pore size of 0.8 mm and rolled in a shot blasting machine to form smooth and dense spherical or near-spherical microspheres (0.3-0.8 mm in diameter). The microspheres are then dried at 45°C for 45 minutes to reduce the moisture content to 2.5%, which is the core. (2) First layer of coating: Prepare the following ingredients: 12% hydrogenated palm oil, 2.5% glyceryl monostearate, 1% hydroxypropyl-β-cyclodextrin, and the remainder water; Hydrogenated palm oil was heated to 65 °C and held for 10 min to completely melt it. Glyceryl monostearate was added and stirred until homogeneous to obtain the oil phase. Hydroxypropyl-β-cyclodextrin was added to water and stirred at 50 °C until dissolved or uniformly dispersed to obtain the aqueous phase. Using a stator-rotor type high-speed shear emulsifier, the aqueous phase was slowly added to the oil phase while maintaining the oil phase temperature at 50 °C and the shearing speed at 8000 r / min. After the aqueous phase was completely added, shearing was continued for 10 min to obtain a water-in-oil emulsion. Using a bottom-spray fluidized bed coating machine, the emulsion was uniformly sprayed onto the core surface. The inlet air temperature was controlled at 45 °C, and the weight gain of the first coating layer was 20% of the core mass.

[0034] (3) Second layer of coating Prepare 64 parts of raw material solid oil (the weight ratio of palmitic acid and hydrogenated oil is 1.4:1), 30 parts of polyacrylic acid resin III with a particle size <80μm, 30 parts of anhydrous ethanol, and excipients (3 parts of talc and 2 parts of triethyl citrate). First, mix polyacrylic acid resin III with a portion of anhydrous ethanol (10 parts) and stir at room temperature for 25 minutes to fully wet and swell the polyacrylic acid resin III, forming a polyacrylic acid resin III swollen product. Separately, add solid oil to the mixing container, heat to 70°C and stir continuously until completely melted, add triethyl citrate and stir evenly. Then, slowly add the polyacrylic acid resin III swollen product to the molten solid oil, stir at 70°C for 15 minutes, then slowly add the remaining anhydrous ethanol, and add talc powder in batches, and continue stirring for 10 minutes to obtain a uniform oil phase polyacrylic acid resin III dispersion.

[0035] The dispersion was used as a coating agent, and a bottom-spray fluidized bed was adopted. The inlet air temperature was 60℃, and the material temperature was maintained at 45℃. The coating weight gain was 40% of the core weight. A second coating was carried out to obtain rumen-protected silymarin.

[0036] Comparative Example 1 A method for preparing uncoated silymarin microgranules, the specific steps of which are as follows: Silymarin powder and magnesium stearate were thoroughly mixed, with the amount of magnesium stearate being 0.75% of the mass of the silymarin powder. A 2% (w / w) hydroxypropyl methylcellulose solution was sprayed onto the mixed powder, and wet granulation was performed to prepare a soft material with a moisture content of 25%. The soft material was extruded through a 0.8 mm sieve and spherically rounded in a shot blasting machine to obtain spherical or near-spherical microspheres with a particle size of 0.3–0.8 mm. The microspheres were dried at 45°C for 45 min to reduce their moisture content to below 3%, resulting in uncoated silymarin microspheres. These uncoated silymarin microspheres, without undergoing a first or second coating, served as a control group sample.

[0037] The rumen-passing rate and small intestinal release rate of silymarin in Example 1 and Comparative Example 1 were determined using the following methods: The rumen degradation rate of rumen-protected silybin was determined using a semi-in vivo nylon bag method. A 10cm × 20cm nylon bag was made of 300-mesh nylon fabric. 7g of rumen-protected silybin sample was accurately weighed into the nylon bag, resulting in a sample volume to surface area ratio of 17.5mg / cm². 2 The incubation times for the samples were 0, 2, 4, 8, 12, 16, 24, 36, and 48 hours. The number of nylon bags at each time point for each sample was 2, 2, 3, 4, 4, 4, 6, 6, and 6 respectively (the number of nylon bags was increased as the disappearance rate increased over time to meet the sample size requirements). After incubation, the nylon bags were removed from the rumen and rinsed together with the 0-hour bags under cold water to stop fermentation and clean the rumen contents until the water was clear. After washing, all nylon bags were dried at 55°C for 48 hours. The dried samples were stored at 4°C for later analysis.

[0038] The rumen degradation rate of silymarin was calculated using the rumen dynamics calculation model based on equation (2): Y = a + b (1 - e) -ct (2).

[0039] In the formula: Y is the degradation rate (%) of a certain nutrient component of the feed after the nylon bag has been retained in the rumen for t (h), a is the rapidly degraded portion (%), b is the slowly degraded portion (%), and c is the degradation rate (% / h) of the slowly degraded portion.

[0040] The formula for calculating the effective degradation rate is shown in equation (3): ED = a + [b × c / (c + k)] (3).

[0041] In the formula: k is the rumen outflow velocity constant of the feed to be tested (% / h). In this experiment, the k value of the sample was assumed to be 0.06% / h.

[0042] The mobile nylon bag method was used to test Holstein dairy cows with duodenal fistulas. Nylon fabric with a pore size of 42 μm was selected, cut into 6 cm × 6 cm pieces, folded in half, and made into 3 cm × 6 cm mobile nylon bags. 0.5 g of the 16-hour residue obtained by the above method was weighed and placed into the mobile nylon bags, which were then sealed using a heat sealer. Three nylon bags were prepared for each cow and each type of feed. The mobile nylon bags were immersed in a 0.004 mol / L hydrochloric acid solution and incubated at 25°C for 1 hour, followed by incubation at 40°C with shaking in a hydrochloric acid solution containing 0.01% (w / v) pepsin for 2 hours. The treated mobile nylon bags were inserted into the duodenal fistula every 30 minutes, with two bags inserted each time. After 24 hours, the mobile nylon bags were collected from the feces, the feces on the bags were cleaned, and they were stored at 20°C. The collected mobile nylon bags were then rinsed under a gentle tap water stream until the water flowing from the bags was clear, bright, and odorless. Finally, rinse the residue in the nylon bag with water to the bottom of the bag; dry at 55℃ for 48 hours, weigh, pack into a sealable plastic bag for storage, and determine the required nutrient components.

[0043] The formula for calculating the small intestinal release rate of different nutrients is shown in equation (4): (4) The rumen content of a nutrient is the amount of that nutrient remaining after 16 hours of rumen degradation.

[0044] The detection methods for silybin in rumen-processed silybin samples, as well as samples after rumen degradation and small intestinal digestion, are as follows: Silymarin detection method The high-performance liquid chromatography (HPLC) conditions were optimized according to the method for determining silymarin content in the 2020 edition of the Pharmacopoeia of the People's Republic of China. The chromatographic column was an Agilent C18 (4.6 mm × 250 mm, 5 μm); the mobile phase was water:methanol = 43:57, 47:53, 53:47 (volume ratio); the flow rate was 0.65 or 0.70 mL / min; the column temperature was 30℃; the detection wavelength was 288 nm; and the injection volume was 20 μL.

[0045] Preparation of standard solutions Standard stock solution: Accurately weigh 20 mg of silymarin standard into a 50 mL volumetric flask, dissolve in methanol and dilute to the mark to obtain a 400 μg / mL silymarin solution. Take 250 μL of the 400 μg / mL silymarin solution into a 10 mL volumetric flask, dissolve in methanol and dilute to the mark, shake well and set aside. The concentration of the obtained silymarin standard stock solution is 10 μg / mL.

[0046] Standard working solutions: Pipette 0.1, 0.5, 1.0, 2.5, and 5.0 mL of silybin standard stock solution into 10 mL volumetric flasks, dilute to the mark with methanol, and shake well to obtain a series of silybin standard working solutions with concentrations of 0.1, 0.5, 1.0, 2.5, and 5.0 μg / mL.

[0047] Standard curve plotting The prepared standard working solutions of 0.1, 0.5, 1.0, 2.5, and 5.0 μg / mL were analyzed under the same liquid chromatography conditions. A standard curve was plotted with silymarin concentration on the x-axis and peak area on the y-axis. The linear regression equation for the silymarin standard curve was obtained, as follows: Figure 1 .

[0048] Sample pretreatment 10g of the rumen-protected silymarin and degraded silymarin sample prepared in Example 1 were pulverized and placed in a stoppered conical flask. 50ml of 75% methanol solution was added, the flask was sealed, and the sample was weighed. Subsequently, the mixture was heated under reflux for 30 minutes, cooled, and weighed again. The weight loss was made up with 75% methanol, the mixture was shaken well, allowed to stand, and filtered through a 0.22μm microporous membrane for analysis by high-performance liquid chromatography (HPLC).

[0049] The results of the determination of rumen-passing silymarin rate and small intestinal release rate in Example 1 are shown in Table 1.

[0050] Table 1

[0051] In Table 1, a represents the rapidly degraded fraction; b represents the slowly degraded fraction; c represents the degradation rate of the slowly degraded fraction; EDSLB represents the effective degradation rate of silybin; RUSLB represents the rumen clearance rate of silybin; and IDSLB represents the small intestinal release rate of silybin.

[0052] The effects of rumen-passed silymarin on the lactation performance of newborn calves are shown in Table 2.

[0053] Table 2

[0054] In Table 2, T represents the treatment effect; D represents the time effect; and T×D represents the interaction effect between treatment and time.

[0055] The effects of rumen-transferring silymarin on blood parameters in newborn cattle are shown in Table 3.

[0056] Table 3

[0057] In Table 3, T represents the treatment effect; D represents the time effect; and T×D represents the interaction effect between treatment and time.

[0058] The effect of rumen-passed silymarin on body condition scores of lactating cows before and after calving, such as Figure 2 , Figure 2 In this context, BCS stands for Body Condition Score; Control group refers to the control group; and Treated group refers to the rumen-treated silymarin group.

[0059] The effect of rumen-transferring silymarin on the disease incidence rate (%) of newborn cattle 21 days postpartum is shown in Table 4.

[0060] Table 4

[0061] 1 is defined as dairy cows with moderate (approximately 40 mg / dL) or high (>80 mg / dL) ketone body concentrations in their urine, and who are treated by a veterinarian with oral propylene glycol; 2. The patient presented with a supine position and muscle tremors, and was given oral Bovikalc (Boehringer Ingelheim, USA).

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing rumen-exposed silymarin, characterized in that, Includes the following steps: (1) Core processing: Silymarin powder is thoroughly mixed with a flow aid, then a binder solution is sprayed onto the mixed powder, wet granulation is used to make a soft material, which is then extruded through a screen, rolled into microspheres, and then dried to obtain the core. (2) First layer of coating: A coating solution is prepared by mixing oil, emulsifier, silymarin absorbent and water; the coating solution is then uniformly sprayed onto the core surface to complete the first coating layer. (3) Second layer of coating Solid oil, polyacrylic acid resin, anhydrous ethanol and excipients are mixed to obtain a dispersion; the dispersion is used as a coating agent for a second coating to obtain rumen-protected silymarin.

2. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The gliding agent in step (1) is magnesium stearate; the adhesive solution is a hydroxypropyl methylcellulose solution with a mass concentration of 1%-3%; and the gliding agent is 0.5%-1% of the mass of silymarin powder.

3. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The moisture content of the soft material in step (1) is 20-25%; the aperture of the sieve is 0.8-1.0 mm; and the particle size of the microspheres is 0.3-0.8 mm.

4. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The drying temperature in step (1) is 40-50℃ and the time is 30-60 minutes. After drying, the moisture content of the microspheres is less than 3%.

5. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The oil mentioned in step (2) is hydrogenated palm oil, the emulsifier is glyceryl monostearate, and the silymarin absorption aid is hydroxypropyl-β-cyclodextrin. The coating solution in step (2) comprises, by weight percentage, 7% to 18% oil, 1% to 4% emulsifier, 1% to 1.5% silymarin absorbent and the remainder water, with the sum of the weight percentages of each component being 100%.

6. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The spraying in step (2) is carried out using a bottom spray fluidized bed coating machine with an inlet temperature of 30-60℃; the first coating layer has a mass of 15%-30% of the core weight.

7. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The solid oil in step (3) is at least one of palmitic acid and hydrogenated oil; the particle size of the polyacrylic acid resin is <80μm, the polyacrylic acid resin is polyacrylic acid resin III, and the excipients are one or more of zinc stearate, magnesium stearate, calcium oxide, talc, polyethylene glycol, glyceryl monostearate, glyceryl distearate, and triethyl citrate.

8. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The mass ratio of the solid grease, polyacrylic acid resin, anhydrous ethanol and excipients in step (3) is 60-65:25-30:25-30:4-5.

9. The method for preparing rumen-passed silymarin according to claim 1, characterized in that, The second coating in step (3) is carried out using a bottom-spray fluidized bed with an inlet air temperature of 50-70℃ and a material temperature of 40-50℃. The coating weight gain is 30%-50% of the core weight.

10. The application of rumen-protected silymarin prepared by any one of claims 1-9 in dairy cow feeding.

Images