Slow-release fat powder for pigs and preparation method thereof

Abstract

The invention belongs to the technical field of feed additives, and particularly relates to slow-release fat powder for pigs and a preparation method of the slow-release fat powder. The slow-release fat powder for pigs comprises an intragastric adhesion-slow release layer, a small intestine forepart bile acid response controlled release layer and a small intestine posterior microbe response controlled release layer. The prepared slow-release fat powder for the pigs is good in stability, accurate release of different nutritional ingredients in different parts of gastrointestinal tracts of the pigs can be achieved, and powerful support is provided for sustainable development of the pig raising industry.

Description

Technical Field

[0001] The invention belongs to the technical field of feed additives, and more specifically relates to a slow-release fat powder for pigs and a preparation method thereof. Background Art

[0002] With rising living standards, the demand for high-quality pork is growing, making precision animal husbandry a key factor in the pig farming industry. Fat is a high-energy nutrient, with each gram of fat produced by oxidation producing approximately twice the energy of carbohydrates and protein. Fat powder plays a vital role in pig farming. First, it provides pigs with high energy, meeting their high energy needs at different stages of growth, promoting their growth and development, and increasing lean meat percentage and pork quality. Second, fat powder improves feed palatability, increasing pigs' feed intake and helping them receive more adequate nutrition. Furthermore, it promotes the absorption of fat-soluble vitamins, safeguarding the pigs' normal physiological functions, immune system, and reproductive performance.

[0003] As an omnivorous animal, the pig's gastrointestinal tract has unique physiological characteristics: the stomach is highly acidic, with a pH value often ranging from 1.5 to 3.5. Although the highly acidic environment is conducive to the initial digestion and sterilization of protein, it can easily lead to the degradation and inactivation of nutrients in the feed; the small intestine can be up to 15-20 times the body length, providing a wide area for digestion and absorption, and the bile acid concentration in the anterior small intestine is significantly higher than that in the posterior small intestine. This distribution characteristic allows fat to be rapidly emulsified and digested in the anterior small intestine; at the same time, the microbial flora enriched in the posterior small intestine can secrete glycosidases to assist in the deep decomposition of carbohydrates. However, most existing pig fat powders are ordinary preparations that are difficult to match the complex digestive environment of the pig's gastrointestinal tract. There are problems such as the easy decomposition of nutrients in the highly acidic stomach environment, uneven fat digestion efficiency in different sections of the small intestine, and inability to coordinate with intestinal microbial metabolism, resulting in low fat utilization and increased breeding costs.

[0004] In view of the above situation, the present invention provides a slow-release fat powder to solve the problem that ordinary fat powder has poor stability and cannot achieve accurate energy release. Summary of the Invention

[0005] The present invention aims to provide a sustained-release fat powder for pigs and a preparation method thereof. Through innovative structural design and ingredient combination, the precise release of different nutrients in different parts of the pig's gastrointestinal tract can be achieved, thereby improving the absorption and utilization rate of nutrients, reducing breeding costs, and improving the growth performance and health level of pigs.

[0006] The invention provides a slow-release fat powder for pigs, comprising: an intragastric adhesion-slow-release layer, a bile acid response controlled-release layer in the anterior small intestine, and a microbial response slow-release layer in the posterior small intestine.

[0007] Preferably, the intragastric adhesion-sustained release layer comprises, by mass: 25-35 parts of xanthan gum, 5-7 parts of porcine gastric mucin, 0.1-0.6 parts of glycine, 0.2-0.4 parts of genipin, 25-35 parts of dopamine hydrochloride, 5-8 parts of sodium butyrate-sodium bicarbonate effervescent microspheres, 10-20 parts of chitosan, and 4-20 parts of pepsin-trehalose crystals@SiO2 nanoparticles.

[0008] Preferably, the bile acid responsive controlled-release layer in the anterior small intestine comprises, by mass: 7-10 parts of sodium cholate, 35-40 parts of dimethylaminoethyl methacrylate, 15-20 parts of ethylene glycol dimethacrylate, 0.1-0.3 parts of azobisisobutyronitrile, 10-19 parts of caprylic acid glyceride; 10-19 parts of capric monoester; 5-7 parts of gelatin, 0.05-0.1 parts of Tween-80, and 0.2-0.5 parts of calcium chloride.

[0009] Preferably, the microbial response sustained-release layer in the posterior small intestine comprises, by mass: 10-15 parts of linoleic acid, 10-15 parts of linolenic acid, 1-3 parts of docosahexaenoic acid, 15-20 parts of palmitic acid, 1-3 parts of vitamin A, 1-3 parts of vitamin E, 0.6-1 parts of lecithin, 0.6-1 parts of Tween 80, 31-58 parts of β-glucan, 0.3-0.8 parts of calcium chloride, 2-4 parts of xanthan gum, and 1-3 parts of gum arabic.

[0010] Preferably, the method for preparing the intragastric adhesion-sustained release layer comprises the following steps:

[0011] S1: xanthan gum, porcine gastric mucin and glycine were added to deionized water, stirred and heated to 50°C; cooled to room temperature, genipin was added, and stirred for 4 hours to form a colloidal matrix;

[0012] S2: Prepare a 10% chitosan ion aqueous solution, dissolve sodium butyrate and sodium bicarbonate in the chitosan solution, spray dry, and spray with sodium alginate to produce sodium butyrate-sodium bicarbonate effervescent microspheres with a diameter of 100–150 μm;

[0013] S3: First, pepsin and trehalose are co-crystallized in a mass ratio of 1:1; the crystals are immersed in a porous SiO2 solution for adsorption loading, and vacuum dried to obtain pepsin-trehalose crystals@SiO2 nanoparticles;

[0014] S4: adding the effervescent microspheres prepared in S2 and the nanoparticles prepared in S3 to the colloidal matrix prepared in S1; stirring uniformly to form a colloidal suspension;

[0015] S5: Polydopamine coating: The colloidal suspension obtained in S4 is placed in tris(hydroxymethylaminomethane) hydrochloride buffer solution, and dopamine hydrochloride is added; the mixture is stirred at 25°C for 12 hours to form a polydopamine coating; the mixture is filtered and washed with pure water to obtain a gastric adhesion-sustained release layer.

[0016] Preferably, the mass ratio of the sodium butyrate to the sodium bicarbonate is 1:1.

[0017] Preferably, the method for preparing the bile acid-responsive controlled-release layer in the anterior small intestine comprises the following steps:

[0018] S1: Sodium hyorhocholate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate were dissolved in a mixture of 40 mL and 10 mL of deionized water; the temperature was controlled at 60°C and the reaction was carried out for 4–6 hours to form a microparticle polymer; the polymer was eluted three times with methanol-acetic acid at a volume ratio of 9:1 until no sodium hyorhocholate residue was detected by HPLC; and the bile acid molecularly imprinted polymer was obtained by vacuum drying.

[0019] S2: Add caprylic acid glyceryl ester and capric acid monoester to 10 mL of a mixed aqueous solution of gelatin and Tween-80, the temperature being controlled at 40°C; and emulsify into small droplets using a high shear emulsifier;

[0020] S3: The polymer particles obtained in S1 were slowly added to the emulsion system prepared in S2, and CaCl2 was added for cross-linking; the reaction was stirred at 40°C for 2 hours to obtain bile acid-responsive controlled-release composite microspheres in the anterior segment of the small intestine; the particle size distribution was controlled at 150–300 μm.

[0021] Preferably, the method for preparing the posterior small intestine microbial response sustained-release layer comprises the following steps:

[0022] S1: Linoleic acid, linolenic acid, docosahexaenoic acid, palmitic acid, vitamin A, vitamin E, lecithin, and Tween-80 were added to 50 mL of deionized water, treated with a high shear homogenizer, and then ultrasonically emulsified for 2.5 hours to obtain nanoemulsified nutrients;

[0023] S2: The nanoemulsified nutrient obtained in S1 was mixed with the β-glucan solution, and 0.2 M CaCl2 solution was added dropwise to crosslink into microgels. The mixture was allowed to stand for 30 minutes to solidify, centrifuged, and washed three times to obtain microgel particles with a particle size of 150–250 μm.

[0024] S3: Dissolve xanthan gum and gum arabic in 10 mL of deionized water, add calcium chloride, stir for 30 minutes, add the microgel particles obtained in S2, stir for 3 hours, and spray dry to obtain the final particles.

[0025] The present invention also provides a method for preparing a slow-release pig fat powder, comprising the following steps:

[0026] S1: Place the microbial response sustained-release layer particles in the posterior small intestine in a fluidized bed and spray them into the bile acid response controlled-release layer microspheres in the anterior small intestine at a pressure of 0.5-1.0 MPa. The inlet air temperature is 25-30°C. Genipin is sprayed simultaneously. The bed temperature is 25°C. The reaction is carried out for 3 hours to form a uniform middle layer.

[0027] S2: Place the intermediate layer particles obtained in S1 in a fluidized bed, spray them into the stomach adhesion-sustained release layer with an inlet air temperature of 40°C, and instantly solidify the outer layer with cold air at 10-15°C to obtain the product.

[0028] Preferably, the mass ratio of the genipin to the anterior small intestine bile acid responsive controlled release layer microspheres is 1:0.005.

[0029] The gastric adhesion-sustained-release layer relies primarily on the acidic environment of the stomach to release nutrients. First, in the acidic environment of the stomach, sodium bicarbonate-sodium bicarbonate effervescent microspheres react with gastric acid to produce carbon dioxide gas, which destroys the microsphere structure, rapidly releasing the sodium butyrate encapsulated therein and simultaneously neutralizing gastric acid to create an optimal pH (2.5-3.5) for pepsin. Chitosan has certain viscosity and gel properties, which can slow the release rate of sodium butyrate and sodium bicarbonate microspheres in the stomach. Pepsin-trehalose crystals are embedded in porous silica to protect pepsin from being active in the suitable acidic environment of the stomach and prevent premature degradation. Xanthan gum is covalently cross-linked with porcine gastric mucin, and polydopamine is protonated at a pH < 3, electrostatically adsorbing to gastric epithelial cells and enhancing adhesion to the gastric wall. This structure simulates the viscoelasticity of the porcine gastric mucus layer, which can prolong the residence time of nutrients in the stomach and enable their full absorption and utilization.

[0030] The design of the bile acid-responsive controlled-release layer in the anterior small intestine is based on the presence of bile acids in the anterior small intestine. The bile acid molecularly imprinted polymer is formed by reacting sodium cholate with dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate under specific conditions. It dissociates when the concentration of cholate exceeds 2 mM, demonstrating specific recognition of the porcine small intestinal environment. When the fat powder enters the anterior small intestine and the concentration of cholate reaches the polymer response threshold, the polymer structure changes, thereby controlling the gradual release of the encapsulated nutrients. Caprylic acid glyceride and capric monoester gradually dissolve and diffuse under the physiological environment of the anterior small intestine, while the gelatin and Tween-80 components help maintain the structural stability of the microspheres and promote nutrient release.

[0031] The release of the microbial-responsive sustained-release layer in the posterior small intestine primarily relies on the microbial activity of the posterior small intestine. Xanthan gum and gum arabic form a three-dimensional network structure through ionic crosslinking under the action of calcium chloride, encapsulating the nutrients protected by β-glucan. This structure is highly stable and remains intact in the physiological environment of the stomach and anterior small intestine, preventing premature release of nutrients. The microbial community in the posterior small intestine secretes xanthanase and arabinanase, which recognize and hydrolyze the β-D-mannuronic acid backbone and α-L-arabinofuranosyl side chains of xanthan gum and gum arabic. These enzymes gradually degrade the microgel network by cleaving glycosidic bonds. As the microgel network is destroyed, the encapsulated nutrients are gradually released into the intestinal lumen. The release rate is influenced by microbial enzyme activity, microgel crosslinking density, and the binding strength between the nutrient and matrix. Because the species and population of microorganisms in the posterior small intestine are relatively stable, the release process is controllable, ensuring efficient absorption of nutrients in specific locations.

[0032] In the three-layer process, genipin is sprayed and evenly distributed on the surface of the microbial-responsive sustained-release layer particles in the posterior small intestine. Upon contact with the bile acid-responsive controlled-release microspheres in the anterior small intestine, the catechol structure of genipin forms a molecular spatial network with the functional groups of the gelatin, polysaccharide, and bile acid molecularly imprinted polymer in both layers. This cross-linked network not only enhances the mechanical strength of the interlayers but also prevents the microgel particles from falling off during processing or storage through steric hindrance. During the fluidized bed process, the microgel particles in the posterior small intestine microbial-responsive sustained-release layer and the composite microspheres in the anterior small intestine controlled-release layer partially interlock through airflow collision. The rough surface of the microgel forms a mechanical interlock with the pores of the controlled-release microspheres, enhancing interfacial bonding. Furthermore, the genipin-induced cross-linking reaction promotes interpenetration of molecular chains at the interface between the two layers, forming a continuous transition zone that further prevents interlayer separation. This stable interlayer bonding ensures that the fat powder is not easily damaged by external physical forces, including mixing, vibration during transportation, and fluctuations in ambient temperature and humidity, maintaining its overall integrity and stability. Furthermore, the stable layered structure helps control the rate of fat release, enabling a slow and sustained release tailored to the needs of pigs at different digestive stages, thereby improving fat utilization.

[0033] Beneficial effects

[0034] Precise targeted release: The three-layer gradient response structure targets the physiological environment characteristics of different parts of the pig's gastrointestinal tract. Through the characteristics of different response materials, it realizes the release of short-chain fatty acids in the stomach, the controlled release of medium-chain fatty acids in the anterior small intestine, and the sustained release of long-chain fatty acids and nutritional fortification factors in the posterior small intestine. It accurately matches the digestion and absorption rules of various parts of the pig's gastrointestinal tract. Compared with traditional fat powder, the fat digestibility exceeds 90%.

[0035] Synergistic effect of ingredients: The nutrients and functional substances in each layer work together. Sodium butyrate and pepsin in the stomach synergistically improve the digestive environment in the stomach; the porcine bile acid produced by the decomposition of bile acid molecular imprinted polymers in the anterior small intestine can enhance the digestion of medium-chain fatty acids; the vitamins and long-chain fatty acids in the posterior small intestine jointly promote the growth and development of pigs. The synergistic effect of multiple ingredients comprehensively improves the health level and growth performance of pigs. Compared with traditional fat powder, the daily weight gain of piglets is increased by 37%.

[0036] Improved stability: In the three-layer process, the catechol structure of genipin forms a molecular spatial network with the functional groups of the gelatin, polysaccharide, and bile acid molecularly imprinted polymer in the gastric release layer and the proto-small intestinal sustained-release layer. The microgel particles in the proto-small intestinal microbial-responsive sustained-release layer and the composite microspheres in the proto-small intestinal controlled-release layer partially interlock through airflow collision in the fluidized bed process, forming a stable interlayer bond. This structure ensures excellent stability of the fat powder during transportation and use.

[0037] In order to explain the present invention more clearly, the technical solutions in the embodiments will be described in detail and accurately in conjunction with the specific cases in the embodiments of the present invention. The embodiments described here are only partial examples of the present invention, not all of them. Based on the embodiments provided by the present invention, all other implementation methods obtained by those skilled in the art without creative work are included in the protection scope of the present invention. The experimental methods in the following embodiments, unless otherwise specified, are conventional methods. The materials, reagents, etc. used in the following examples and comparative examples, unless otherwise specified, are purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. DETAILED DESCRIPTION

[0038] Example 1

[0039] Example 1 provides a sustained-release fat powder for pigs, comprising: a gastric adhesion-sustained-release layer, a bile acid-responsive controlled-release layer in the anterior small intestine, and a microbial-responsive sustained-release layer in the posterior small intestine.

[0040] The preparation method of the slow-release pig fat powder comprises the following steps:

[0041] S1: Place the microbial response sustained-release layer particles in the posterior small intestine in a fluidized bed and spray them into the bile acid response controlled-release layer microspheres in the anterior small intestine at a pressure of 0.6 MPa. The inlet air temperature is 28°C. Genipin is sprayed simultaneously. The bed temperature is 25°C. The reaction is carried out for 3 hours to form a uniform intermediate layer.

[0042] S2: Place the intermediate layer particles obtained in S1 in a fluidized bed, spray them into the stomach adhesion-sustained release layer at an inlet air temperature of 40°C, and instantly solidify the outer layer with cold air at 12°C to obtain the product.

[0043] The intragastric adhesion-sustained release layer includes, by mass, 30 parts of xanthan gum, 6 parts of porcine gastric mucin, 0.3 parts of glycine, 0.3 parts of genipin, 30 parts of dopamine hydrochloride, 6 parts of sodium butyrate-sodium bicarbonate effervescent microspheres, 16 parts of chitosan, and 11.4 parts of pepsin-trehalose crystals@SiO2 nanoparticles.

[0044] The bile acid responsive controlled-release layer for the anterior small intestine comprises, by weight: 8 parts of sodium hyodolic acid, 38 parts of dimethylaminoethyl methacrylate, 17 parts of ethylene glycol dimethacrylate, 0.2 parts of azobisisobutyronitrile, 15 parts of caprylic acid glyceride, 15.3 parts of capric monoester, 6 parts of gelatin, 0.08 parts of Tween-80, and 0.42 parts of calcium chloride.

[0045] The microbial response sustained-release layer in the posterior small intestine includes, by weight, 13 parts of linoleic acid, 13 parts of linolenic acid, 2 parts of docosahexaenoic acid, 18 parts of palmitic acid, 2 parts of vitamin A, 2 parts of vitamin E, 0.8 parts of lecithin, 0.8 parts of Tween 80, 42.9 parts of beta-glucan, 0.5 parts of calcium chloride, 3 parts of xanthan gum, and 2 parts of gum arabic.

[0046] The preparation method of the intragastric adhesion-sustained release layer comprises the following steps:

[0047] S1: xanthan gum, porcine gastric mucin and glycine were added to deionized water, stirred and heated to 50°C; cooled to room temperature, genipin was added, and stirred for 4 hours to form a colloidal matrix;

[0048] S2: Prepare a 10% chitosan ion aqueous solution, dissolve sodium butyrate and sodium bicarbonate in the chitosan solution, spray dry, and spray sodium alginate to obtain sodium butyrate-sodium bicarbonate effervescent microspheres with a diameter of 100–150 μm.

[0049] S3: First, pepsin and trehalose are co-crystallized in a mass ratio of 1:1; the crystals are immersed in a porous SiO2 solution (pore size 5 nm) for adsorption loading, and vacuum dried to obtain pepsin-trehalose crystals@SiO2 nanoparticles.

[0050] S4: adding the effervescent microspheres prepared in S2 and the nanoparticles prepared in S3 to the colloidal matrix prepared in S1; stirring evenly to form a colloidal suspension.

[0051] S5: Polydopamine coating: The colloidal suspension obtained in S4 was placed in tris(hydroxymethylaminomethane) hydrochloride buffer (pH 8.5), and dopamine hydrochloride was added; the mixture was stirred at 25°C for 12 hours to form a polydopamine coating; the mixture was filtered and washed with pure water to obtain a gastric adhesion-sustained release layer.

[0052] The preparation method of the bile acid-responsive controlled-release layer in the anterior small intestine comprises the following steps:

[0053] S1: Sodium hyorhocholate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate were dissolved in a mixture of 40 mL and 10 mL of deionized water; the temperature was controlled at 60°C and the reaction was carried out for 4 hours to form a particulate polymer; the mixture was eluted with methanol-acetic acid (9:1, v / v) three times until no sodium hyorhocholate residue was detected by HPLC; and the bile acid molecularly imprinted polymer was obtained by vacuum drying.

[0054] S2: Add caprylic acid glyceryl ester and capric acid monoester to 10 mL of a mixed aqueous solution of gelatin and Tween-80, and control the temperature at 40°C; use a high shear emulsifier (10,000 rpm, 3 min) to emulsify into small droplets.

[0055] S3: The polymer particles obtained in S1 were slowly added to the emulsion system prepared in S2, and CaCl2 was added for cross-linking; the reaction was stirred at 40°C for 2 hours to obtain bile acid-responsive controlled-release composite microspheres in the anterior segment of the small intestine; the particle size distribution was controlled at 150–300 μm.

[0056] The method for preparing the microbial response sustained-release layer in the posterior small intestine comprises the following steps:

[0057] S1: Linoleic acid, linolenic acid, docosahexaenoic acid, palmitic acid, vitamin A, vitamin E, lecithin, and Tween-80 were added to 50 mL of deionized water, treated with a high shear homogenizer, and then ultrasonically emulsified for 2.5 hours to obtain nanoemulsified nutrients;

[0058] S2: The nanoemulsified nutrient obtained in S1 was mixed with the β-glucan solution, and 0.2 M CaCl2 solution was added dropwise to crosslink into microgels. The mixture was allowed to stand for 30 minutes to solidify, centrifuged, and washed three times to obtain microgel particles with a particle size of 150–250 μm.

[0059] S3: Dissolve xanthan gum and gum arabic in 10 mL of deionized water, add calcium chloride, stir for 30 minutes, add the microgel particles obtained in S2, stir for 3 hours, and spray dry to obtain the final particles.

[0060] In the preparation method of the sustained-release pig fat powder, the mass ratio of genipin to the bile acid-responsive controlled-release microspheres in the anterior small intestine is 1:0.005.

[0061] In the preparation method of the intragastric adhesion-sustained release layer, the mass ratio of sodium butyrate to sodium bicarbonate is 1:1.

[0062] Example 2

[0063] Example 2 provides a sustained-release pig fat powder comprising a gastric adhesion-sustained-release layer, a bile acid-responsive controlled-release layer in the anterior small intestine, and a microbial-responsive sustained-release layer in the posterior small intestine. This differs from Example 1 in the preparation method's process parameters and the ratios of the various material components.

[0064] The preparation method of the slow-release pig fat powder comprises the following steps:

[0065] S1: Place the microbial response sustained-release layer particles in the posterior small intestine in a fluidized bed and spray them into the bile acid response controlled-release layer microspheres in the anterior small intestine at a pressure of 0.5 MPa. The inlet air temperature is 25°C. Genipin is sprayed simultaneously. The bed temperature is 25°C. The reaction is carried out for 3 hours to form a uniform middle layer.

[0066] S2: Place the intermediate layer particles obtained in S1 in a fluidized bed, spray them into the stomach adhesion-sustained release layer with an inlet air temperature of 40°C, and instantly solidify the outer layer with cold air at 10°C to obtain the product.

[0067] The intragastric adhesion-sustained release layer includes, by mass, 25 parts of xanthan gum, 5 parts of porcine gastric mucin, 0.1 parts of glycine, 0.2 parts of genipin, 25 parts of dopamine hydrochloride, 5 parts of sodium butyrate-sodium bicarbonate effervescent microspheres, 20 parts of chitosan, and 19.7 parts of pepsin-trehalose crystals@SiO2 nanoparticles.

[0068] The bile acid responsive controlled-release layer for the anterior small intestine comprises, by weight, 7 parts of sodium hyodolic acid, 35 parts of dimethylaminoethyl methacrylate, 16 parts of ethylene glycol dimethacrylate, 0.15 parts of azobisisobutyronitrile, 18.3 parts of caprylic acid glyceride, 18.3 parts of capric monoester, 5 parts of gelatin, 0.05 parts of Tween-80, and 0.2 parts of calcium chloride.

[0069] The microbial response sustained-release layer in the posterior small intestine includes, by weight, 10 parts of linoleic acid, 10 parts of linolenic acid, 1 part of docosahexaenoic acid, 15 parts of palmitic acid, 1 part of vitamin A, 1 part of vitamin E, 0.6 parts of lecithin, 0.6 parts of Tween 80, 57.5 parts of β-glucan, 0.3 parts of calcium chloride, 2 parts of xanthan gum, and 1 part of gum arabic.

[0070] The preparation method of the intragastric adhesion-sustained release layer comprises the following steps:

[0071] S1: xanthan gum, porcine gastric mucin and glycine were added to deionized water, stirred and heated to 50°C; cooled to room temperature, genipin was added, and stirred for 4 hours to form a colloidal matrix;

[0072] S2: Prepare a 10% chitosan ion aqueous solution, dissolve sodium butyrate and sodium bicarbonate in the chitosan solution, spray dry, and spray sodium alginate to obtain sodium butyrate-sodium bicarbonate effervescent microspheres with a diameter of 100–150 μm.

[0073] S3: First, pepsin and trehalose are co-crystallized in a mass ratio of 1:1; the crystals are immersed in a porous SiO2 solution (pore size 5 nm) for adsorption loading, and vacuum dried to obtain pepsin-trehalose crystals@SiO2 nanoparticles.

[0074] S4: adding the effervescent microspheres prepared in S2 and the nanoparticles prepared in S3 to the colloidal matrix prepared in S1; stirring evenly to form a colloidal suspension.

[0075] S5: Polydopamine coating: The colloidal suspension obtained in S4 was placed in tris(hydroxymethylaminomethane) hydrochloride buffer (pH 8.5), and dopamine hydrochloride was added; the mixture was stirred at 25°C for 12 hours to form a polydopamine coating; the mixture was filtered and washed with pure water to obtain a gastric adhesion-sustained release layer.

[0076] The preparation method of the bile acid-responsive controlled-release layer in the anterior small intestine comprises the following steps:

[0077] S1: Sodium hyorhocholate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate were dissolved in a mixture of 40 mL and 10 mL of deionized water; the temperature was controlled at 60°C and the reaction was carried out for 4 hours to form a particulate polymer; the mixture was eluted with methanol-acetic acid (9:1, v / v) three times until no sodium hyorhocholate residue was detected by HPLC; and the bile acid molecularly imprinted polymer was obtained by vacuum drying.

[0078] S2: Add caprylic acid glyceryl ester and capric acid monoester to 10 mL of a mixed aqueous solution of gelatin and Tween-80, and control the temperature at 40°C; use a high shear emulsifier (10,000 rpm, 3 min) to emulsify into small droplets.

[0079] S3: The polymer particles obtained in S1 were slowly added to the emulsion system prepared in S2, and CaCl2 was added for cross-linking; the reaction was stirred at 40°C for 2 hours to obtain bile acid-responsive controlled-release composite microspheres in the anterior segment of the small intestine; the particle size distribution was controlled at 150–300 μm.

[0080] The method for preparing the microbial response sustained-release layer in the posterior small intestine comprises the following steps:

[0081] S1: Linoleic acid, linolenic acid, docosahexaenoic acid, palmitic acid, vitamin A, vitamin E, lecithin, and Tween-80 were added to 50 mL of deionized water, treated with a high shear homogenizer, and then ultrasonically emulsified for 2.5 hours to obtain nanoemulsified nutrients;

[0082] S2: The nanoemulsified nutrient obtained in S1 was mixed with the β-glucan solution, and 0.2 M CaCl2 solution was added dropwise to crosslink into microgels. The mixture was allowed to stand for 30 minutes to solidify, centrifuged, and washed three times to obtain microgel particles with a particle size of 150–250 μm.

[0083] S3: Dissolve xanthan gum and gum arabic in 10 mL of deionized water, add calcium chloride, stir for 30 minutes, add the microgel particles obtained in S2, stir for 3 hours, and spray dry to obtain the final particles.

[0084] In the preparation method of the sustained-release pig fat powder, the mass ratio of genipin to the bile acid-responsive controlled-release microspheres in the anterior small intestine is 1:0.005.

[0085] In the preparation method of the intragastric adhesion-sustained release layer, the mass ratio of sodium butyrate to sodium bicarbonate is 1:1.

[0086] Example 3

[0087] Example 3 provides a sustained-release pig fat powder comprising a gastric adhesion-sustained-release layer, a bile acid-responsive controlled-release layer in the anterior small intestine, and a microbial-responsive sustained-release layer in the posterior small intestine. This differs from Example 1 in that the preparation method employs different process parameters and incorporates different ratios of the various material components.

[0088] The preparation method of the slow-release pig fat powder comprises the following steps:

[0089] S1: Place the microbial response sustained-release layer particles in the posterior small intestine in a fluidized bed and spray them into the bile acid response controlled-release layer microspheres in the anterior small intestine at a pressure of 1 MPa. The inlet air temperature is 30°C. Genipin is sprayed simultaneously. The bed temperature is 25°C. The reaction is carried out for 3 hours to form a uniform intermediate layer.

[0090] S2: Place the intermediate layer particles obtained in S1 in a fluidized bed, spray them into the stomach adhesion-sustained release layer with an inlet air temperature of 40°C, and instantly solidify the outer layer with cold air at 15°C to obtain the product.

[0091] The intragastric adhesion-sustained release layer includes, by mass, 35 parts of xanthan gum, 7 parts of porcine gastric mucin, 0.6 parts of glycine, 0.4 parts of genipin, 35 parts of dopamine hydrochloride, 8 parts of sodium butyrate-sodium bicarbonate effervescent microspheres, 10 parts of chitosan, and 4 parts of pepsin-trehalose crystals@SiO2 nanoparticles.

[0092] The bile acid-responsive controlled-release layer for the anterior small intestine comprises, by weight, 10 parts of sodium hyodolic acid, 40 parts of dimethylaminoethyl methacrylate, 19 parts of ethylene glycol dimethacrylate, 0.25 parts of azobisisobutyronitrile, 11.5 parts of caprylic acid glyceride, 11.68 parts of capric monoester, 7 parts of gelatin, 0.07 parts of Tween-80, and 0.5 parts of calcium chloride.

[0093] The microbial response sustained-release layer in the posterior small intestine includes, by weight, 15 parts of linoleic acid, 15 parts of linolenic acid, 3 parts of docosahexaenoic acid, 20 parts of palmitic acid, 3 parts of vitamin A, 3 parts of vitamin E, 1 part of lecithin, 1 part of Tween 80, 31.2 parts of beta-glucan, 0.8 part of calcium chloride, 4 parts of xanthan gum, and 3 parts of gum arabic.

[0094] The preparation method of the intragastric adhesion-sustained release layer comprises the following steps:

[0095] S1: xanthan gum, porcine gastric mucin and glycine were added to deionized water, stirred and heated to 50°C; cooled to room temperature, genipin was added, and stirred for 4 hours to form a colloidal matrix;

[0096] S2: Prepare a 10% chitosan ion aqueous solution, dissolve sodium butyrate and sodium bicarbonate in the chitosan solution, spray dry, and spray sodium alginate to obtain sodium butyrate-sodium bicarbonate effervescent microspheres with a diameter of 100–150 μm.

[0097] S3: First, pepsin and trehalose are co-crystallized in a mass ratio of 1:1; the crystals are immersed in a porous SiO2 solution (pore size 5 nm) for adsorption loading, and vacuum dried to obtain pepsin-trehalose crystals@SiO2 nanoparticles.

[0098] S4: adding the effervescent microspheres prepared in S2 and the nanoparticles prepared in S3 to the colloidal matrix prepared in S1; stirring evenly to form a colloidal suspension.

[0099] S5: Polydopamine coating: The colloidal suspension obtained in S4 was placed in tris(hydroxymethylaminomethane) hydrochloride buffer (pH 8.5), and dopamine hydrochloride was added; the mixture was stirred at 25°C for 12 hours to form a polydopamine coating; the mixture was filtered and washed with pure water to obtain a gastric adhesion-sustained release layer.

[0100] The preparation method of the bile acid-responsive controlled-release layer in the anterior small intestine comprises the following steps:

[0101] S1: Sodium hyorhocholate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate were dissolved in a mixture of 40 mL and 10 mL of deionized water; the temperature was controlled at 60°C and the reaction was carried out for 4 hours to form a particulate polymer; the mixture was eluted with methanol-acetic acid (9:1, v / v) three times until no sodium hyorhocholate residue was detected by HPLC; and the bile acid molecularly imprinted polymer was obtained by vacuum drying.

[0102] S2: Add caprylic acid glyceryl ester and capric acid monoester to 10 mL of a mixed aqueous solution of gelatin and Tween-80, and control the temperature at 40°C; use a high shear emulsifier (10,000 rpm, 3 min) to emulsify into small droplets.

[0103] S3: The polymer particles obtained in S1 were slowly added to the emulsion system prepared in S2, and CaCl2 was added for cross-linking; the reaction was stirred at 40°C for 2 hours to obtain bile acid-responsive controlled-release composite microspheres in the anterior segment of the small intestine; the particle size distribution was controlled at 150–300 μm.

[0104] The method for preparing the posterior small intestinal microbial response sustained-release layer comprises the following steps:

[0105] S1: Linoleic acid, linolenic acid, docosahexaenoic acid, palmitic acid, vitamin A, vitamin E, lecithin, and Tween-80 were added to 50 mL of deionized water, treated with a high shear homogenizer, and then ultrasonically emulsified for 2.5 hours to obtain nanoemulsified nutrients;

[0106] S2: The nanoemulsified nutrient obtained in S1 was mixed with the β-glucan solution, and 0.2 M CaCl2 solution was added dropwise to crosslink into microgels. The mixture was allowed to stand for 30 minutes to solidify, centrifuged, and washed three times to obtain microgel particles with a particle size of 150–250 μm.

[0107] S3: Dissolve xanthan gum and gum arabic in 10 mL of deionized water, add calcium chloride, stir for 30 minutes, add the microgel particles obtained in S2, stir for 3 hours, and spray dry to obtain the final particles.

[0108] In the preparation method of the sustained-release pig fat powder, the mass ratio of genipin to the bile acid-responsive controlled-release microspheres in the anterior small intestine is 1:0.005.

[0109] In the preparation method of the intragastric adhesion-sustained release layer, the mass ratio of sodium butyrate to sodium bicarbonate is 1:1.

[0110] Comparative Example 1

[0111] Comparative Example 1 provides an uncoated ordinary fat powder.

[0112] The preparation method of the uncoated common fat powder is as follows:

[0113] The mixture is prepared by directly and evenly mixing sodium butyrate, pepsin, glycine, caprylic acid glyceride, capric acid monoester, linoleic acid, linolenic acid, docosahexaenoic acid, palmitic acid, vitamin A and vitamin E, with the mass ratio being the same as that in Example 1.

[0114] Comparative Example 2

[0115] Comparative Example 2 provides a single-layer coated fat powder, comprising: a microbial response sustained-release layer in the posterior small intestine and other nutrients.

[0116] The preparation method of the single-layer coated fat powder comprises the following steps:

[0117] The posterior small intestine microbial response sustained-release layer is directly and evenly mixed with sodium butyrate, pepsin, glycine, caprylic acid glyceride, and capric acid monoester, and the mass ratio is the same as that in Example 1.

[0118] The preparation method of the microbial response sustained-release layer in the posterior small intestine is the same as that in Example 1.

[0119] Comparative Example 3

[0120] Comparative Example 3 provides a double-layer coated fat powder, including: a bile acid response controlled release layer in the anterior small intestine and a microbial response sustained release layer in the posterior small intestine, as well as other nutrients.

[0121] The preparation method of the double-layer coated fat powder comprises the following steps:

[0122] The bile acid-responsive controlled-release layer in the anterior small intestine and the microbial-responsive sustained-release layer in the posterior small intestine were combined according to the method in Example 1 to obtain a composition, and then the composition was directly mixed with pepsin, sodium butyrate and glycine in the same mass ratio as in Example 1.

[0123] The preparation methods of the bile acid-responsive controlled-release layer in the anterior small intestine and the microbial-responsive sustained-release layer in the posterior small intestine are the same as those in Example 1.

[0124] The fat powder prepared in Example 1 and the fat powders of Comparative Examples 1-3 were subjected to experiments simulating the pig gastrointestinal environment. The experimental results are shown in Tables 2 and 3. The specific experimental methods are as follows:

[0125] The experimental conditions for simulating the release of nutrients in each layer were set as follows: the fat powders of Example 1 and Comparative Examples 1-3 were added to four constant-temperature magnetic stirring reaction vessels, the temperature was set to 37±0.5°C, hydrochloric acid / sodium bicarbonate buffer was added, the pH value was changed from 2.5→5.8→6.6 (switching time ≤ 5 minutes), and the magnetic stirring speed was adjusted to simulate the environments of pig gastric juice, the anterior small intestine, and the posterior small intestine, respectively. The specific experimental parameter settings are shown in Table 1.

[0126] Table 1 Parameter settings for simulation experiment on nutrient release in each layer

[0127]

[0128] Testing steps:

[0129] Gastric juice samples: After centrifugation and filtration, sodium butyrate was detected directly by UV spectrophotometry at a wavelength of 205 nm. Gastric juice sampling time points: 0.5, 1, 1.5, and 2 hours;

[0130] Small intestinal samples were homogenized and extracted with a methanol:chloroform (2:1, v / v) mixture by oscillation. The organic phase was collected after centrifugation and concentrated to dryness under nitrogen purge. The supernatant was centrifuged and methylated with concentrated sulfuric acid-methanol (5% v / v) for HPLC analysis. HPLC conditions included: C18 reversed-phase column (4.6 mm × 250 mm, 5 μm); mobile phase: acetonitrile-0.1% phosphoric acid (60:40, v / v); flow rate: 1.0 mL / min; detection wavelength: 254 nm. Sampling time points for the anterior small intestine were 3, 4, 5, and 6 hours; sampling time points for the posterior small intestine were 8, 12, 18, and 24 hours.

[0131] Each group took 5 mL of medium each time and immediately added an equal volume of fresh medium. The test results are shown in Tables 2 and 3.

[0132] Table 2 Cumulative release rate of sodium butyrate in gastric fluid environment of Example 1 and Comparative Examples 1-3

[0133] Group 0.5 hours 1 hour 1.5 hours 2 hours Example 1 27.5％ 55.8％ 82.5％ 95.5％ Comparative Example 1 82.6％ 95.6％ 96.2％ 96.5％ Comparative Example 2 74.6％ 89.4％ 94.3％ 95.8％ Comparative Example 3 68.9％ 83.5％ 93.9％ 96.3％

[0134] Table 3 Cumulative release rate of nutrients in each layer of the gastrointestinal tract of Example 1 and Comparative Examples 1-3

[0135]

[0136]

[0137] The release kinetics curve of the gastric release was fitted from 0 to 1.5 hours. 2 =0.98, k0=55% / h, which is consistent with the zero-order kinetic release model. It can be seen from Table 1 that the use of a gastric-soluble polymer as a carrier does not affect the release rate. However, the short-chain fatty acids in Comparative Examples 1-3 did not use a gastric-soluble polymer carrier, and the release rates of sodium butyrate exceeded 60% at 0.5 h, posing a significant risk of burst release.

[0138] From the results in Table 3, it can be seen that the 2-hour cumulative release rate of the gastric adhesion-sustained-release layer of the fat powder provided in Example 1 reaches 90%, the 6-hour cumulative release rate of the medium-chain fatty acids in the bile acid response controlled-release layer in the anterior small intestine is only 15%, while the 6-hour cumulative release rates of the medium-chain fatty acids in Comparative Examples 1-3 all exceed 45%; the 24-hour cumulative release rate of the long-chain fatty acids in the microbial response sustained-release layer in the posterior small intestine is only 20%, while the 24-hour cumulative release rates of the long-chain fatty acids in Comparative Examples 1-3 all exceed 50%. This shows that the fat powder structure provided in Example 1 has a good sustained-release effect and can achieve precise release of nutrients. Comparative Examples 1-3 do not use a sustained-release structure or partially use a sustained-release structure and cannot achieve the effect of precise release of nutrients.

[0139] In vitro mechanical stability tests were performed on Example 1 and Comparative Examples 1-3. The test method was as follows:

[0140] The specific method is based on the Chinese Pharmacopoeia. High-speed stirring simulation: the fat powders of Example 1 and Comparative Examples 1-3 were placed in a 500 rpm stirrer for 30 minutes. The breakage rate was determined using a Malvern 3000 laser particle size analyzer to detect changes in particle size distribution and calculate the fragmentation ratio (D90 / D10 ratio change). The test results are shown in Table 4.

[0141] Table 4 Stability test results of Example 1 and Comparative Examples 1-3

[0142] Group Initial particle size (μm) Particle size after stirring (μm) Fragmentation ratio (%) Example 1 150±12 155±15 8.2±1.5 Comparative Example 1 148±10 210±25 42.7±3.8 Comparative Example 2 152±11 185±20 28.5±2.6 Comparative Example 3 154±13 170±18 18.9±2.1

[0143] As shown in Table 4, after 30 minutes of high-speed stirring, the fragment ratio of Example 1 was only 8%, while the fragment ratios of Comparative Examples 1-3 all reached more than 19%, indicating that the three-layer gradient response structure of the fat powder provided by Example 1 has good stability.

[0144] Actual breeding experiments were conducted on Example 1 and Comparative Examples 1-3 to test three core indicators: daily weight gain, feed conversion rate, and fat digestibility. The experimental results are shown in Table 5.

[0145] The experimental method is as follows:

[0146] Animal selection: A total of 200 healthy weaned piglets (8-10 kg) were randomly divided into 4 groups, with 50 pigs in each group (half male and half female);

[0147] Group settings:

[0148] Control group: basal diet (without experimental fat powder);

[0149] Experimental group 1: basic diet + fat powder of Example 1 (addition amount 3%);

[0150] Experimental group 2: basic diet + fat powder of comparative example 1 (addition amount 3%);

[0151] Experimental group 3: basic diet + fat powder of comparative example 2 (addition amount 3%);

[0152] Experimental group 4: basic diet + fat powder of comparative example 3 (added amount 3%).

[0153] Experimental cycle and feeding management:

[0154] Adaptation period: 7 days, gradual transition to experimental diet);

[0155] The formal period was 28 days, with free access to food and water, an ambient temperature of 25±2℃, and a humidity of 65%;

[0156] Data recording: feed intake was recorded daily, weights were weighed weekly, and fecal samples were collected regularly.

[0157] Measurement indicators and methods

[0158] Daily weight gain: The body weight was weighed after fasting for 12 hours at the beginning and end of the experiment to calculate the total weight gain;

[0159] Daily weight gain (g / d) = (final weight - initial weight) / number of experimental days.

[0160] Feed conversion rate = total feed intake (kg) / total weight gain (kg);

[0161] Fat digestibility: Fecal samples were collected for three consecutive days, dried, and ground, and the acid-insoluble ash (AIA) content was determined. Fat digestibility (%) = [1 - (AIA in feed / AIA in feces) × (fat in feces / fat in feed)] × 100.

[0162] Table 5 Actual breeding experimental results of Example 1 and Comparative Examples 1-3

[0163]

[0164]

[0165] From the data in the table, it can be seen that: when fed with the fat powder provided in Example 1, the daily weight gain of the experimental group of piglets was significantly improved, which was 36.8% higher than that of the control group and 30% higher than that of the comparative example 1; the feed conversion rate was reduced by 46% compared with the comparative example 1, thereby reducing the breeding cost; the fat digestibility exceeded 90%, which was 15.2% higher than that of the comparative example 1, further proving that the three-layer sustained-release structure can effectively prolong the nutrient release time, improve feed utilization, and reduce breeding costs.

[0166] The above is a preferred embodiment of the present invention. It should be noted that those skilled in the art can make a series of improvements and modifications based on the principles of the present invention. These improvements and modifications based on the principles of the present invention are also covered by the scope of protection of the present invention.

Claims

1. A sustained-release fat powder for pigs, characterized in that: include: Gastric adhesion-sustained release layer, bile acid response controlled release layer in the anterior small intestine, and microbial response sustained release layer in the posterior small intestine.

2. The sustained-release fat powder for pigs according to claim 1, characterized in that: The intragastric adhesion-sustained release layer comprises, by weight, 25-35 parts of xanthan gum, 5-7 parts of porcine gastric mucin, 0.1-0.6 parts of glycine, 0.2-0.4 parts of genipin, 25-35 parts of dopamine hydrochloride, 5-8 parts of sodium butyrate-sodium bicarbonate effervescent microspheres, 10-20 parts of chitosan, and 4-20 parts of pepsin-trehalose crystals@SiO2 nanoparticles.

3. The sustained-release fat powder for pigs according to claim 1, characterized in that: The bile acid-responsive controlled-release layer for the anterior small intestine comprises, by weight, 7-10 parts of sodium hyodolic acid, 35-40 parts of dimethylaminoethyl methacrylate, 15-20 parts of ethylene glycol dimethacrylate, 0.1-0.3 parts of azobisisobutyronitrile, 10-19 parts of caprylic acid glyceride, 10-19 parts of capric acid monoester, 5-7 parts of gelatin, 0.05-0.1 parts of Tween-80, and 0.2-0.5 parts of calcium chloride.

4. The sustained-release fat powder for pigs according to claim 1, characterized in that: The microbial response sustained-release layer in the posterior small intestine includes, by weight, 10-15 parts of linoleic acid, 10-15 parts of linolenic acid, 1-3 parts of docosahexaenoic acid, 15-20 parts of palmitic acid, 1-3 parts of vitamin A, 1-3 parts of vitamin E, 0.6-1 parts of lecithin, 0.6-1 parts of Tween 80, 31-58 parts of beta-glucan, 0.3-0.8 parts of calcium chloride, 2-4 parts of xanthan gum, and 1-3 parts of gum arabic.

5. The sustained-release fat powder for pigs according to claim 1, characterized in that: The preparation method of the intragastric adhesion-sustained release layer comprises the following steps: S1: xanthan gum, porcine gastric mucin and glycine were added to deionized water, stirred and heated to 50°C; cooled to room temperature, genipin was added, and stirred for 4 hours to form a colloidal matrix; S2: Prepare a 10% chitosan ion aqueous solution, dissolve sodium butyrate and sodium bicarbonate in the chitosan solution, spray dry, and spray with sodium alginate to produce sodium butyrate-sodium bicarbonate effervescent microspheres with a diameter of 100–150 μm; S3: First, pepsin and trehalose are co-crystallized in a mass ratio of 1:1; the crystals are immersed in a porous SiO2 solution for adsorption loading, and vacuum dried to obtain pepsin-trehalose crystals@SiO2 nanoparticles; S4: adding the effervescent microspheres prepared in S2 and the nanoparticles prepared in S3 to the colloidal matrix prepared in S1; stirring uniformly to form a colloidal suspension; S5: Polydopamine coating: The colloidal suspension obtained in S4 is placed in tris(hydroxymethylaminomethane) hydrochloride buffer solution, and dopamine hydrochloride is added; the mixture is stirred at 25°C for 12 hours to form a polydopamine coating; the mixture is filtered and washed with pure water to obtain a gastric adhesion-sustained release layer.

6. The sustained-release fat powder for pigs according to claim 5, characterized in that: Calculated by mass, the mass ratio of the sodium butyrate to the sodium bicarbonate is 1:

1.

7. The sustained-release fat powder for pigs according to claim 1, characterized in that: The preparation method of the bile acid-responsive controlled-release layer in the anterior small intestine comprises the following steps: S1: Sodium hyorhocholate, dimethylaminoethyl methacrylate, and ethylene glycol dimethacrylate were dissolved in a mixture of 40 mL and 10 mL of deionized water; the temperature was controlled at 60°C and the reaction was carried out for 4–6 hours to form a microparticle polymer; the polymer was eluted three times with methanol-acetic acid at a volume ratio of 9:1 until no sodium hyorhocholate residue was detected by HPLC; and the bile acid molecularly imprinted polymer was obtained by vacuum drying. S2: Add caprylic acid glyceryl ester and capric acid monoester to 10 mL of a mixed aqueous solution of gelatin and Tween-80, the temperature being controlled at 40°C; and emulsify into small droplets using a high shear emulsifier; S3: The polymer particles obtained in S1 were slowly added to the emulsion system prepared in S2, and CaCl2 was added for cross-linking; the reaction was stirred at 40°C for 2 hours to obtain bile acid-responsive controlled-release composite microspheres in the anterior segment of the small intestine; the particle size distribution was controlled at 150–300 μm.

8. The sustained-release fat powder for pigs according to claim 1, characterized in that: The method for preparing the microbial response sustained-release layer in the posterior small intestine comprises the following steps: S1: Linoleic acid, linolenic acid, docosahexaenoic acid, palmitic acid, vitamin A, vitamin E, lecithin, and Tween-80 were added to 50 mL of deionized water, treated with a high shear homogenizer, and then ultrasonically emulsified for 2.5 hours to obtain nanoemulsified nutrients; S2: The nanoemulsified nutrient obtained in S1 was mixed with the β-glucan solution, and 0.2 M CaCl2 solution was added dropwise to crosslink into microgels. The mixture was allowed to stand for 30 minutes to solidify, centrifuged, and washed three times to obtain microgel particles with a particle size of 150–250 μm. S3: Dissolve xanthan gum and gum arabic in 10 mL of deionized water, add calcium chloride, stir for 30 minutes, add the microgel particles obtained in S2, stir for 3 hours, and spray dry to obtain the final particles.

9. The method for preparing the sustained-release fat powder for pigs according to any one of claims 1 to 8, characterized in that: The steps include: S1: Place the microbial response sustained-release layer particles in the posterior small intestine in a fluidized bed and spray them into the bile acid response controlled-release layer microspheres in the anterior small intestine at a pressure of 0.5-1.0 MPa. The inlet air temperature is 25-30°C. Genipin is sprayed simultaneously. The bed temperature is 25°C. The reaction is carried out for 3 hours to form a uniform middle layer. S2: Place the intermediate layer particles obtained in S1 in a fluidized bed, spray them into the stomach adhesion-sustained release layer with an inlet air temperature of 40°C, and instantly solidify the outer layer with cold air at 10-15°C to obtain the product.

10. The method for preparing the slow-release fat powder for pigs according to claim 9, characterized in that: The mass ratio of genipin to the bile acid-responsive controlled-release microspheres in the anterior small intestine is 1:0.005.

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